# Copyright (C) 2001-2024, Python Software Foundation
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#
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# josix, 2018
# Steven Hsu , 2021
msgid ""
msgstr ""
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"PO-Revision-Date: 2022-12-26 23:12+0800\n"
"Last-Translator: Adrian Liaw \n"
"Language-Team: Chinese - TAIWAN (https://github.com/python/python-docs-zh-"
"tw)\n"
"Language: zh_TW\n"
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"X-Generator: Poedit 3.2.2\n"
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#: ../../tutorial/classes.rst:5
msgid "Classes"
msgstr "Class"
#: ../../tutorial/classes.rst:7
msgid ""
"Classes provide a means of bundling data and functionality together. "
"Creating a new class creates a new *type* of object, allowing new "
"*instances* of that type to be made. Each class instance can have "
"attributes attached to it for maintaining its state. Class instances can "
"also have methods (defined by its class) for modifying its state."
msgstr ""
"Class class \\ *"
" (type)*\\ * (instance)* class "
" (attribute)Class class "
"method"
#: ../../tutorial/classes.rst:13
msgid ""
"Compared with other programming languages, Python's class mechanism adds "
"classes with a minimum of new syntax and semantics. It is a mixture of the "
"class mechanisms found in C++ and Modula-3. Python classes provide all the "
"standard features of Object Oriented Programming: the class inheritance "
"mechanism allows multiple base classes, a derived class can override any "
"methods of its base class or classes, and a method can call the method of a "
"base class with the same name. Objects can contain arbitrary amounts and "
"kinds of data. As is true for modules, classes partake of the dynamic "
"nature of Python: they are created at runtime, and can be modified further "
"after creation."
msgstr ""
"Python class class "
" C++ Modula-3 class Python class "
" (Object Oriented Programming) class base "
"class derived class (override) base "
"class method method base class "
"methodclass "
"Python (runtime) "
#: ../../tutorial/classes.rst:23
msgid ""
"In C++ terminology, normally class members (including the data members) are "
"*public* (except see below :ref:`tut-private`), and all member functions are "
"*virtual*. As in Modula-3, there are no shorthands for referencing the "
"object's members from its methods: the method function is declared with an "
"explicit first argument representing the object, which is provided "
"implicitly by the call. As in Smalltalk, classes themselves are objects. "
"This provides semantics for importing and renaming. Unlike C++ and "
"Modula-3, built-in types can be used as base classes for extension by the "
"user. Also, like in C++, most built-in operators with special syntax "
"(arithmetic operators, subscripting etc.) can be redefined for class "
"instances."
msgstr ""
" C++ class \\ **\\ "
":ref:`tut-private`\\ \\ **\\ "
"Modula-3 Python method "
"method (explicit)"
" (implicitly) Smalltak class "
"import C++ Modula-3Pyhon "
" base class (extension) C++ "
" class "
#: ../../tutorial/classes.rst:34
msgid ""
"(Lacking universally accepted terminology to talk about classes, I will make "
"occasional use of Smalltalk and C++ terms. I would use Modula-3 terms, "
"since its object-oriented semantics are closer to those of Python than C++, "
"but I expect that few readers have heard of it.)"
msgstr ""
" class Smalltalk C++ "
" Modula-3 C++ Python "
""
#: ../../tutorial/classes.rst:43
msgid "A Word About Names and Objects"
msgstr ""
#: ../../tutorial/classes.rst:45
msgid ""
"Objects have individuality, and multiple names (in multiple scopes) can be "
"bound to the same object. This is known as aliasing in other languages. "
"This is usually not appreciated on a first glance at Python, and can be "
"safely ignored when dealing with immutable basic types (numbers, strings, "
"tuples). However, aliasing has a possibly surprising effect on the "
"semantics of Python code involving mutable objects such as lists, "
"dictionaries, and most other types. This is usually used to the benefit of "
"the program, since aliases behave like pointers in some respects. For "
"example, passing an object is cheap since only a pointer is passed by the "
"implementation; and if a function modifies an object passed as an argument, "
"the caller will see the change --- this eliminates the need for two "
"different argument passing mechanisms as in Pascal."
msgstr ""
" (individuality) (scope) "
" (aliasing) Python "
"tuple"
" listdictionary"
" Python "
" (pointer)"
" "
"(caller) Pascal "
#: ../../tutorial/classes.rst:61
msgid "Python Scopes and Namespaces"
msgstr "Python (Scope) (Namespace)"
#: ../../tutorial/classes.rst:63
msgid ""
"Before introducing classes, I first have to tell you something about "
"Python's scope rules. Class definitions play some neat tricks with "
"namespaces, and you need to know how scopes and namespaces work to fully "
"understand what's going on. Incidentally, knowledge about this subject is "
"useful for any advanced Python programmer."
msgstr ""
" class Python Class "
"definition"
""
" Python "
#: ../../tutorial/classes.rst:69
msgid "Let's begin with some definitions."
msgstr ""
#: ../../tutorial/classes.rst:71
msgid ""
"A *namespace* is a mapping from names to objects. Most namespaces are "
"currently implemented as Python dictionaries, but that's normally not "
"noticeable in any way (except for performance), and it may change in the "
"future. Examples of namespaces are: the set of built-in names (containing "
"functions such as :func:`abs`, and built-in exception names); the global "
"names in a module; and the local names in a function invocation. In a sense "
"the set of attributes of an object also form a namespace. The important "
"thing to know about namespaces is that there is absolutely no relation "
"between names in different namespaces; for instance, two different modules "
"may both define a function ``maximize`` without confusion --- users of the "
"modules must prefix it with the module name."
msgstr ""
"**\\ Python "
"dictionary "
" :func:`abs` "
" (global) (local) "
""
" "
"``maximize`` (prefix) "
#: ../../tutorial/classes.rst:82
msgid ""
"By the way, I use the word *attribute* for any name following a dot --- for "
"example, in the expression ``z.real``, ``real`` is an attribute of the "
"object ``z``. Strictly speaking, references to names in modules are "
"attribute references: in the expression ``modname.funcname``, ``modname`` is "
"a module object and ``funcname`` is an attribute of it. In this case there "
"happens to be a straightforward mapping between the module's attributes and "
"the global names defined in the module: they share the same namespace! [#]_"
msgstr ""
"\\ * (attribute)* (dot) "
" ``z.real````real`` ``z`` "
" ``modname.funcname`` ``modname`` "
" ``funcname`` "
"[#]_"
#: ../../tutorial/classes.rst:90
msgid ""
"Attributes may be read-only or writable. In the latter case, assignment to "
"attributes is possible. Module attributes are writable: you can write "
"``modname.the_answer = 42``. Writable attributes may also be deleted with "
"the :keyword:`del` statement. For example, ``del modname.the_answer`` will "
"remove the attribute :attr:`!the_answer` from the object named by "
"``modname``."
msgstr ""
""
" ``modname.the_answer = 42`` :keyword:`del` "
"``del modname.the_answer`` ``modname`` "
" :attr:`!the_answer`"
#: ../../tutorial/classes.rst:96
msgid ""
"Namespaces are created at different moments and have different lifetimes. "
"The namespace containing the built-in names is created when the Python "
"interpreter starts up, and is never deleted. The global namespace for a "
"module is created when the module definition is read in; normally, module "
"namespaces also last until the interpreter quits. The statements executed "
"by the top-level invocation of the interpreter, either read from a script "
"file or interactively, are considered part of a module called :mod:"
"`__main__`, so they have their own global namespace. (The built-in names "
"actually also live in a module; this is called :mod:`builtins`.)"
msgstr ""
" Python "
""
""
" (top-level invocation) "
" :mod:`__main__` "
" :mod:`builtins`"
#: ../../tutorial/classes.rst:106
msgid ""
"The local namespace for a function is created when the function is called, "
"and deleted when the function returns or raises an exception that is not "
"handled within the function. (Actually, forgetting would be a better way to "
"describe what actually happens.) Of course, recursive invocations each have "
"their own local namespace."
msgstr ""
""
""
" (recursive invocation) "
#: ../../tutorial/classes.rst:112
msgid ""
"A *scope* is a textual region of a Python program where a namespace is "
"directly accessible. \"Directly accessible\" here means that an unqualified "
"reference to a name attempts to find the name in the namespace."
msgstr ""
"**\\ Python (textual region)"
" "
"(unqualified reference) "
#: ../../tutorial/classes.rst:116
msgid ""
"Although scopes are determined statically, they are used dynamically. At any "
"time during execution, there are 3 or 4 nested scopes whose namespaces are "
"directly accessible:"
msgstr ""
""
" 3 4 "
#: ../../tutorial/classes.rst:120
msgid "the innermost scope, which is searched first, contains the local names"
msgstr ""
#: ../../tutorial/classes.rst:121
msgid ""
"the scopes of any enclosing functions, which are searched starting with the "
"nearest enclosing scope, contain non-local, but also non-global names"
msgstr ""
" (enclosing function) "
" (non-local) (non-global) "
#: ../../tutorial/classes.rst:123
msgid "the next-to-last scope contains the current module's global names"
msgstr ""
#: ../../tutorial/classes.rst:124
msgid ""
"the outermost scope (searched last) is the namespace containing built-in "
"names"
msgstr ""
#: ../../tutorial/classes.rst:126
msgid ""
"If a name is declared global, then all references and assignments go "
"directly to the next-to-last scope containing the module's global names. To "
"rebind variables found outside of the innermost scope, the :keyword:"
"`nonlocal` statement can be used; if not declared nonlocal, those variables "
"are read-only (an attempt to write to such a variable will simply create a "
"*new* local variable in the innermost scope, leaving the identically named "
"outer variable unchanged)."
msgstr ""
""
" :keyword:"
"`nonlocal` nonlocal"
"\\ **\\ "
""
#: ../../tutorial/classes.rst:133
msgid ""
"Usually, the local scope references the local names of the (textually) "
"current function. Outside functions, the local scope references the same "
"namespace as the global scope: the module's namespace. Class definitions "
"place yet another namespace in the local scope."
msgstr ""
""
"Class definition "
""
#: ../../tutorial/classes.rst:138
msgid ""
"It is important to realize that scopes are determined textually: the global "
"scope of a function defined in a module is that module's namespace, no "
"matter from where or by what alias the function is called. On the other "
"hand, the actual search for names is done dynamically, at run time --- "
"however, the language definition is evolving towards static name resolution, "
"at \"compile\" time, so don't rely on dynamic name resolution! (In fact, "
"local variables are already determined statically.)"
msgstr ""
""
""
" (run time) "
" (compile time) (static name resolution)"
" (dynamic name resolution) "
#: ../../tutorial/classes.rst:146
msgid ""
"A special quirk of Python is that -- if no :keyword:`global` or :keyword:"
"`nonlocal` statement is in effect -- assignments to names always go into the "
"innermost scope. Assignments do not copy data --- they just bind names to "
"objects. The same is true for deletions: the statement ``del x`` removes "
"the binding of ``x`` from the namespace referenced by the local scope. In "
"fact, all operations that introduce new names use the local scope: in "
"particular, :keyword:`import` statements and function definitions bind the "
"module or function name in the local scope."
msgstr ""
" Python :keyword:`global` :keyword:`nonlocal` "
" (assignment) "
" ``del x`` "
" ``x`` "
" :keyword:`import` "
#: ../../tutorial/classes.rst:154
msgid ""
"The :keyword:`global` statement can be used to indicate that particular "
"variables live in the global scope and should be rebound there; the :keyword:"
"`nonlocal` statement indicates that particular variables live in an "
"enclosing scope and should be rebound there."
msgstr ""
":keyword:`global` "
":keyword:`nonlocal` "
""
#: ../../tutorial/classes.rst:162
msgid "Scopes and Namespaces Example"
msgstr ""
#: ../../tutorial/classes.rst:164
msgid ""
"This is an example demonstrating how to reference the different scopes and "
"namespaces, and how :keyword:`global` and :keyword:`nonlocal` affect "
"variable binding::"
msgstr ""
" :keyword:`global` :"
"keyword:`nonlocal` ::"
#: ../../tutorial/classes.rst:168
msgid ""
"def scope_test():\n"
" def do_local():\n"
" spam = \"local spam\"\n"
"\n"
" def do_nonlocal():\n"
" nonlocal spam\n"
" spam = \"nonlocal spam\"\n"
"\n"
" def do_global():\n"
" global spam\n"
" spam = \"global spam\"\n"
"\n"
" spam = \"test spam\"\n"
" do_local()\n"
" print(\"After local assignment:\", spam)\n"
" do_nonlocal()\n"
" print(\"After nonlocal assignment:\", spam)\n"
" do_global()\n"
" print(\"After global assignment:\", spam)\n"
"\n"
"scope_test()\n"
"print(\"In global scope:\", spam)"
msgstr ""
#: ../../tutorial/classes.rst:191
msgid "The output of the example code is:"
msgstr ""
#: ../../tutorial/classes.rst:193
msgid ""
"After local assignment: test spam\n"
"After nonlocal assignment: nonlocal spam\n"
"After global assignment: nonlocal spam\n"
"In global scope: global spam"
msgstr ""
#: ../../tutorial/classes.rst:200
msgid ""
"Note how the *local* assignment (which is default) didn't change "
"*scope_test*\\'s binding of *spam*. The :keyword:`nonlocal` assignment "
"changed *scope_test*\\'s binding of *spam*, and the :keyword:`global` "
"assignment changed the module-level binding."
msgstr ""
"**\\ *scope_test* *spam* :"
"keyword:`nonlocal` *scope_test* *spam* :keyword:"
"`global` "
#: ../../tutorial/classes.rst:205
msgid ""
"You can also see that there was no previous binding for *spam* before the :"
"keyword:`global` assignment."
msgstr " :keyword:`global` *spam* "
#: ../../tutorial/classes.rst:212
msgid "A First Look at Classes"
msgstr " class"
#: ../../tutorial/classes.rst:214
msgid ""
"Classes introduce a little bit of new syntax, three new object types, and "
"some new semantics."
msgstr "Class "
#: ../../tutorial/classes.rst:221
msgid "Class Definition Syntax"
msgstr "Class definition"
#: ../../tutorial/classes.rst:223
msgid "The simplest form of class definition looks like this::"
msgstr "Class definition ::"
#: ../../tutorial/classes.rst:225
msgid ""
"class ClassName:\n"
" \n"
" .\n"
" .\n"
" .\n"
" "
msgstr ""
"class ClassName:\n"
" \n"
" .\n"
" .\n"
" .\n"
" "
#: ../../tutorial/classes.rst:232
msgid ""
"Class definitions, like function definitions (:keyword:`def` statements) "
"must be executed before they have any effect. (You could conceivably place "
"a class definition in a branch of an :keyword:`if` statement, or inside a "
"function.)"
msgstr ""
"Class definition\\ :keyword:`def` "
" class definition :keyword:`if` "
""
#: ../../tutorial/classes.rst:236
msgid ""
"In practice, the statements inside a class definition will usually be "
"function definitions, but other statements are allowed, and sometimes useful "
"--- we'll come back to this later. The function definitions inside a class "
"normally have a peculiar form of argument list, dictated by the calling "
"conventions for methods --- again, this is explained later."
msgstr ""
"class definition "
"Class "
" method "
#: ../../tutorial/classes.rst:242
msgid ""
"When a class definition is entered, a new namespace is created, and used as "
"the local scope --- thus, all assignments to local variables go into this "
"new namespace. In particular, function definitions bind the name of the new "
"function here."
msgstr ""
" class definition"
""
""
#: ../../tutorial/classes.rst:247
msgid ""
"When a class definition is left normally (via the end), a *class object* is "
"created. This is basically a wrapper around the contents of the namespace "
"created by the class definition; we'll learn more about class objects in the "
"next section. The original local scope (the one in effect just before the "
"class definition was entered) is reinstated, and the class object is bound "
"here to the class name given in the class definition header (:class:`!"
"ClassName` in the example)."
msgstr ""
" class definition *class *\\ "
" (wrapper) class definition "
" class class definition "
" class class definition "
" class :class:`!ClassName`\\ "
#: ../../tutorial/classes.rst:259
msgid "Class Objects"
msgstr "Class "
#: ../../tutorial/classes.rst:261
msgid ""
"Class objects support two kinds of operations: attribute references and "
"instantiation."
msgstr ""
"Class (attribute reference) "
"(instantiation)"
#: ../../tutorial/classes.rst:264
msgid ""
"*Attribute references* use the standard syntax used for all attribute "
"references in Python: ``obj.name``. Valid attribute names are all the names "
"that were in the class's namespace when the class object was created. So, "
"if the class definition looked like this::"
msgstr ""
"**\\ Python ``obj.name``"
" class class class "
"definition ::"
#: ../../tutorial/classes.rst:269
msgid ""
"class MyClass:\n"
" \"\"\"A simple example class\"\"\"\n"
" i = 12345\n"
"\n"
" def f(self):\n"
" return 'hello world'"
msgstr ""
"class MyClass:\n"
" \"\"\"\"\"\"\n"
" i = 12345\n"
"\n"
" def f(self):\n"
" return 'hello world'"
#: ../../tutorial/classes.rst:276
msgid ""
"then ``MyClass.i`` and ``MyClass.f`` are valid attribute references, "
"returning an integer and a function object, respectively. Class attributes "
"can also be assigned to, so you can change the value of ``MyClass.i`` by "
"assignment. :attr:`!__doc__` is also a valid attribute, returning the "
"docstring belonging to the class: ``\"A simple example class\"``."
msgstr ""
" ``MyClass.i`` ``MyClass.f`` "
"Class (assign) "
"``MyClass.i`` :attr:`!__doc__` class "
" (docstring)``\"A simple example class\"``"
#: ../../tutorial/classes.rst:282
msgid ""
"Class *instantiation* uses function notation. Just pretend that the class "
"object is a parameterless function that returns a new instance of the class. "
"For example (assuming the above class)::"
msgstr ""
"Class **\\ (function notation) class "
" class class ::"
#: ../../tutorial/classes.rst:286 ../../tutorial/classes.rst:303
msgid "x = MyClass()"
msgstr "x = MyClass()"
#: ../../tutorial/classes.rst:288
msgid ""
"creates a new *instance* of the class and assigns this object to the local "
"variable ``x``."
msgstr " class \\ ** ``x``"
#: ../../tutorial/classes.rst:291
msgid ""
"The instantiation operation (\"calling\" a class object) creates an empty "
"object. Many classes like to create objects with instances customized to a "
"specific initial state. Therefore a class may define a special method named :"
"meth:`~object.__init__`, like this::"
msgstr ""
" class class "
"class :meth:"
"`~object.__init__` method ::"
#: ../../tutorial/classes.rst:296
msgid ""
"def __init__(self):\n"
" self.data = []"
msgstr ""
"def __init__(self):\n"
" self.data = []"
#: ../../tutorial/classes.rst:299
msgid ""
"When a class defines an :meth:`~object.__init__` method, class instantiation "
"automatically invokes :meth:`!__init__` for the newly created class "
"instance. So in this example, a new, initialized instance can be obtained "
"by::"
msgstr ""
" class :meth:`~object.__init__` methodclass "
"class :meth:`!__init__`"
" ::"
#: ../../tutorial/classes.rst:305
msgid ""
"Of course, the :meth:`~object.__init__` method may have arguments for "
"greater flexibility. In that case, arguments given to the class "
"instantiation operator are passed on to :meth:`!__init__`. For example, ::"
msgstr ""
":meth:`~object.__init__` method "
" class :meth:`!__init__` ::"
#: ../../tutorial/classes.rst:309
msgid ""
">>> class Complex:\n"
"... def __init__(self, realpart, imagpart):\n"
"... self.r = realpart\n"
"... self.i = imagpart\n"
"...\n"
">>> x = Complex(3.0, -4.5)\n"
">>> x.r, x.i\n"
"(3.0, -4.5)"
msgstr ""
">>> class Complex:\n"
"... def __init__(self, realpart, imagpart):\n"
"... self.r = realpart\n"
"... self.i = imagpart\n"
"...\n"
">>> x = Complex(3.0, -4.5)\n"
">>> x.r, x.i\n"
"(3.0, -4.5)"
#: ../../tutorial/classes.rst:322
msgid "Instance Objects"
msgstr ""
#: ../../tutorial/classes.rst:324
msgid ""
"Now what can we do with instance objects? The only operations understood by "
"instance objects are attribute references. There are two kinds of valid "
"attribute names: data attributes and methods."
msgstr ""
""
" (data attribute) method"
#: ../../tutorial/classes.rst:328
msgid ""
"*data attributes* correspond to \"instance variables\" in Smalltalk, and to "
"\"data members\" in C++. Data attributes need not be declared; like local "
"variables, they spring into existence when they are first assigned to. For "
"example, if ``x`` is the instance of :class:`!MyClass` created above, the "
"following piece of code will print the value ``16``, without leaving a "
"trace::"
msgstr ""
"**\\ Smalltalk C++ "
""
" ``x`` :class:`!MyClass` "
"``16`` ::"
#: ../../tutorial/classes.rst:334
msgid ""
"x.counter = 1\n"
"while x.counter < 10:\n"
" x.counter = x.counter * 2\n"
"print(x.counter)\n"
"del x.counter"
msgstr ""
"x.counter = 1\n"
"while x.counter < 10:\n"
" x.counter = x.counter * 2\n"
"print(x.counter)\n"
"del x.counter"
#: ../../tutorial/classes.rst:340
msgid ""
"The other kind of instance attribute reference is a *method*. A method is a "
"function that \"belongs to\" an object."
msgstr ""
#: ../../tutorial/classes.rst:345
msgid ""
"Valid method names of an instance object depend on its class. By "
"definition, all attributes of a class that are function objects define "
"corresponding methods of its instances. So in our example, ``x.f`` is a "
"valid method reference, since ``MyClass.f`` is a function, but ``x.i`` is "
"not, since ``MyClass.i`` is not. But ``x.f`` is not the same thing as "
"``MyClass.f`` --- it is a *method object*, not a function object."
msgstr ""
" method class class "
" method``x.f`` "
"method ``MyClass.f`` ``x.i`` ``MyClass."
"i`` ``x.f`` ``MyClass.f`` *method *"
""
#: ../../tutorial/classes.rst:356
msgid "Method Objects"
msgstr "Method "
#: ../../tutorial/classes.rst:358
msgid "Usually, a method is called right after it is bound::"
msgstr " method ::"
#: ../../tutorial/classes.rst:360
msgid "x.f()"
msgstr "x.f()"
#: ../../tutorial/classes.rst:362
msgid ""
"In the :class:`!MyClass` example, this will return the string ``'hello "
"world'``. However, it is not necessary to call a method right away: ``x.f`` "
"is a method object, and can be stored away and called at a later time. For "
"example::"
msgstr ""
" :class:`!MyClass` ``'hello world'``"
" method``x.f`` method "
" ::"
#: ../../tutorial/classes.rst:366
msgid ""
"xf = x.f\n"
"while True:\n"
" print(xf())"
msgstr ""
"xf = x.f\n"
"while True:\n"
" print(xf())"
#: ../../tutorial/classes.rst:370
msgid "will continue to print ``hello world`` until the end of time."
msgstr " ``hello world`` "
#: ../../tutorial/classes.rst:372
msgid ""
"What exactly happens when a method is called? You may have noticed that ``x."
"f()`` was called without an argument above, even though the function "
"definition for :meth:`!f` specified an argument. What happened to the "
"argument? Surely Python raises an exception when a function that requires an "
"argument is called without any --- even if the argument isn't actually "
"used..."
msgstr ""
" method ``x.f()`` "
" :meth:`!f` "
"Python "
"..."
#: ../../tutorial/classes.rst:378
msgid ""
"Actually, you may have guessed the answer: the special thing about methods "
"is that the instance object is passed as the first argument of the "
"function. In our example, the call ``x.f()`` is exactly equivalent to "
"``MyClass.f(x)``. In general, calling a method with a list of *n* arguments "
"is equivalent to calling the corresponding function with an argument list "
"that is created by inserting the method's instance object before the first "
"argument."
msgstr ""
"method "
"``x.f()`` ``MyClass.f(x)``"
" *n* method "
"(argument list) method "
#: ../../tutorial/classes.rst:385
msgid ""
"In general, methods work as follows. When a non-data attribute of an "
"instance is referenced, the instance's class is searched. If the name "
"denotes a valid class attribute that is a function object, references to "
"both the instance object and the function object are packed into a method "
"object. When the method object is called with an argument list, a new "
"argument list is constructed from the instance object and the argument list, "
"and the function object is called with this new argument list."
msgstr ""
""
" class class "
""
""
#: ../../tutorial/classes.rst:398
msgid "Class and Instance Variables"
msgstr "Class "
#: ../../tutorial/classes.rst:400
msgid ""
"Generally speaking, instance variables are for data unique to each instance "
"and class variables are for attributes and methods shared by all instances "
"of the class::"
msgstr ""
" class class "
" method ::"
#: ../../tutorial/classes.rst:404
msgid ""
"class Dog:\n"
"\n"
" kind = 'canine' # class variable shared by all instances\n"
"\n"
" def __init__(self, name):\n"
" self.name = name # instance variable unique to each instance\n"
"\n"
">>> d = Dog('Fido')\n"
">>> e = Dog('Buddy')\n"
">>> d.kind # shared by all dogs\n"
"'canine'\n"
">>> e.kind # shared by all dogs\n"
"'canine'\n"
">>> d.name # unique to d\n"
"'Fido'\n"
">>> e.name # unique to e\n"
"'Buddy'"
msgstr ""
#: ../../tutorial/classes.rst:422
msgid ""
"As discussed in :ref:`tut-object`, shared data can have possibly surprising "
"effects with involving :term:`mutable` objects such as lists and "
"dictionaries. For example, the *tricks* list in the following code should "
"not be used as a class variable because just a single list would be shared "
"by all *Dog* instances::"
msgstr ""
"\\ :ref:`tut-object`\\ :term:`mutable` "
" list dictionary *tricks* "
"list class list *Dog* "
" ::"
#: ../../tutorial/classes.rst:428
msgid ""
"class Dog:\n"
"\n"
" tricks = [] # mistaken use of a class variable\n"
"\n"
" def __init__(self, name):\n"
" self.name = name\n"
"\n"
" def add_trick(self, trick):\n"
" self.tricks.append(trick)\n"
"\n"
">>> d = Dog('Fido')\n"
">>> e = Dog('Buddy')\n"
">>> d.add_trick('roll over')\n"
">>> e.add_trick('play dead')\n"
">>> d.tricks # unexpectedly shared by all dogs\n"
"['roll over', 'play dead']"
msgstr ""
#: ../../tutorial/classes.rst:445
msgid "Correct design of the class should use an instance variable instead::"
msgstr " class ::"
#: ../../tutorial/classes.rst:447
msgid ""
"class Dog:\n"
"\n"
" def __init__(self, name):\n"
" self.name = name\n"
" self.tricks = [] # creates a new empty list for each dog\n"
"\n"
" def add_trick(self, trick):\n"
" self.tricks.append(trick)\n"
"\n"
">>> d = Dog('Fido')\n"
">>> e = Dog('Buddy')\n"
">>> d.add_trick('roll over')\n"
">>> e.add_trick('play dead')\n"
">>> d.tricks\n"
"['roll over']\n"
">>> e.tricks\n"
"['play dead']"
msgstr ""
#: ../../tutorial/classes.rst:469
msgid "Random Remarks"
msgstr ""
#: ../../tutorial/classes.rst:473
msgid ""
"If the same attribute name occurs in both an instance and in a class, then "
"attribute lookup prioritizes the instance::"
msgstr ""
" class "
" ::"
#: ../../tutorial/classes.rst:476
msgid ""
">>> class Warehouse:\n"
"... purpose = 'storage'\n"
"... region = 'west'\n"
"...\n"
">>> w1 = Warehouse()\n"
">>> print(w1.purpose, w1.region)\n"
"storage west\n"
">>> w2 = Warehouse()\n"
">>> w2.region = 'east'\n"
">>> print(w2.purpose, w2.region)\n"
"storage east"
msgstr ""
">>> class Warehouse:\n"
"... purpose = 'storage'\n"
"... region = 'west'\n"
"...\n"
">>> w1 = Warehouse()\n"
">>> print(w1.purpose, w1.region)\n"
"storage west\n"
">>> w2 = Warehouse()\n"
">>> w2.region = 'east'\n"
">>> print(w2.purpose, w2.region)\n"
"storage east"
#: ../../tutorial/classes.rst:488
msgid ""
"Data attributes may be referenced by methods as well as by ordinary users "
"(\"clients\") of an object. In other words, classes are not usable to "
"implement pure abstract data types. In fact, nothing in Python makes it "
"possible to enforce data hiding --- it is all based upon convention. (On "
"the other hand, the Python implementation, written in C, can completely hide "
"implementation details and control access to an object if necessary; this "
"can be used by extensions to Python written in C.)"
msgstr ""
" method "
"class Python "
" C Python "
" C Python "
""
#: ../../tutorial/classes.rst:496
msgid ""
"Clients should use data attributes with care --- clients may mess up "
"invariants maintained by the methods by stamping on their data attributes. "
"Note that clients may add data attributes of their own to an instance object "
"without affecting the validity of the methods, as long as name conflicts are "
"avoided --- again, a naming convention can save a lot of headaches here."
msgstr ""
" "
"method "
" method "
""
#: ../../tutorial/classes.rst:502
msgid ""
"There is no shorthand for referencing data attributes (or other methods!) "
"from within methods. I find that this actually increases the readability of "
"methods: there is no chance of confusing local variables and instance "
"variables when glancing through a method."
msgstr ""
" method method"
" method method "
#: ../../tutorial/classes.rst:507
msgid ""
"Often, the first argument of a method is called ``self``. This is nothing "
"more than a convention: the name ``self`` has absolutely no special meaning "
"to Python. Note, however, that by not following the convention your code "
"may be less readable to other Python programmers, and it is also conceivable "
"that a *class browser* program might be written that relies upon such a "
"convention."
msgstr ""
" ``self````self`` "
"Python "
" Python "
" *class (browser)* "
#: ../../tutorial/classes.rst:513
msgid ""
"Any function object that is a class attribute defines a method for instances "
"of that class. It is not necessary that the function definition is "
"textually enclosed in the class definition: assigning a function object to a "
"local variable in the class is also ok. For example::"
msgstr ""
" class class method"
" class definition class "
" ::"
#: ../../tutorial/classes.rst:518
msgid ""
"# Function defined outside the class\n"
"def f1(self, x, y):\n"
" return min(x, x+y)\n"
"\n"
"class C:\n"
" f = f1\n"
"\n"
" def g(self):\n"
" return 'hello world'\n"
"\n"
" h = g"
msgstr ""
#: ../../tutorial/classes.rst:530
msgid ""
"Now ``f``, ``g`` and ``h`` are all attributes of class :class:`!C` that "
"refer to function objects, and consequently they are all methods of "
"instances of :class:`!C` --- ``h`` being exactly equivalent to ``g``. Note "
"that this practice usually only serves to confuse the reader of a program."
msgstr ""
" ``f````g`` ``h`` class :class:`!C` "
"class :class:`!C` method ``h`` ``g`` "
""
#: ../../tutorial/classes.rst:535
msgid ""
"Methods may call other methods by using method attributes of the ``self`` "
"argument::"
msgstr "Method ``self`` method method ::"
#: ../../tutorial/classes.rst:538
msgid ""
"class Bag:\n"
" def __init__(self):\n"
" self.data = []\n"
"\n"
" def add(self, x):\n"
" self.data.append(x)\n"
"\n"
" def addtwice(self, x):\n"
" self.add(x)\n"
" self.add(x)"
msgstr ""
"class Bag:\n"
" def __init__(self):\n"
" self.data = []\n"
"\n"
" def add(self, x):\n"
" self.data.append(x)\n"
"\n"
" def addtwice(self, x):\n"
" self.add(x)\n"
" self.add(x)"
#: ../../tutorial/classes.rst:549
msgid ""
"Methods may reference global names in the same way as ordinary functions. "
"The global scope associated with a method is the module containing its "
"definition. (A class is never used as a global scope.) While one rarely "
"encounters a good reason for using global data in a method, there are many "
"legitimate uses of the global scope: for one thing, functions and modules "
"imported into the global scope can be used by methods, as well as functions "
"and classes defined in it. Usually, the class containing the method is "
"itself defined in this global scope, and in the next section we'll find some "
"good reasons why a method would want to reference its own class."
msgstr ""
"Method method "
"class "
"method "
"import method "
"class method class"
" method class "
#: ../../tutorial/classes.rst:559
msgid ""
"Each value is an object, and therefore has a *class* (also called its "
"*type*). It is stored as ``object.__class__``."
msgstr ""
" *class* *type*"
" ``object.__class__`` "
#: ../../tutorial/classes.rst:566
msgid "Inheritance"
msgstr " (Inheritance)"
#: ../../tutorial/classes.rst:568
msgid ""
"Of course, a language feature would not be worthy of the name \"class\" "
"without supporting inheritance. The syntax for a derived class definition "
"looks like this::"
msgstr ""
"class class "
"derived class ::"
#: ../../tutorial/classes.rst:572
msgid ""
"class DerivedClassName(BaseClassName):\n"
" \n"
" .\n"
" .\n"
" .\n"
" "
msgstr ""
"class DerivedClassName(BaseClassName):\n"
" \n"
" .\n"
" .\n"
" .\n"
" "
#: ../../tutorial/classes.rst:579
msgid ""
"The name :class:`!BaseClassName` must be defined in a namespace accessible "
"from the scope containing the derived class definition. In place of a base "
"class name, other arbitrary expressions are also allowed. This can be "
"useful, for example, when the base class is defined in another module::"
msgstr ""
" :class:`!BaseClassName` "
" derived class base class"
" base class "
" ::"
#: ../../tutorial/classes.rst:585
msgid "class DerivedClassName(modname.BaseClassName):"
msgstr "class DerivedClassName(modname.BaseClassName):"
#: ../../tutorial/classes.rst:587
msgid ""
"Execution of a derived class definition proceeds the same as for a base "
"class. When the class object is constructed, the base class is remembered. "
"This is used for resolving attribute references: if a requested attribute is "
"not found in the class, the search proceeds to look in the base class. This "
"rule is applied recursively if the base class itself is derived from some "
"other class."
msgstr ""
" derived class base class class "
"base class "
"class base class base class "
" class"
#: ../../tutorial/classes.rst:593
msgid ""
"There's nothing special about instantiation of derived classes: "
"``DerivedClassName()`` creates a new instance of the class. Method "
"references are resolved as follows: the corresponding class attribute is "
"searched, descending down the chain of base classes if necessary, and the "
"method reference is valid if this yields a function object."
msgstr ""
" derived class ``DerivedClassName()`` "
"class Method class "
" base class method "
""
#: ../../tutorial/classes.rst:599
msgid ""
"Derived classes may override methods of their base classes. Because methods "
"have no special privileges when calling other methods of the same object, a "
"method of a base class that calls another method defined in the same base "
"class may end up calling a method of a derived class that overrides it. "
"(For C++ programmers: all methods in Python are effectively ``virtual``.)"
msgstr ""
"Derived class base class method method "
" method base class method "
"base class method derived "
"class method C++ Python method "
"``virtual``"
#: ../../tutorial/classes.rst:605
msgid ""
"An overriding method in a derived class may in fact want to extend rather "
"than simply replace the base class method of the same name. There is a "
"simple way to call the base class method directly: just call ``BaseClassName."
"methodname(self, arguments)``. This is occasionally useful to clients as "
"well. (Note that this only works if the base class is accessible as "
"``BaseClassName`` in the global scope.)"
msgstr ""
" derived class method base "
"class method base class method "
" ``BaseClassName.methodname(self, arguments)``"
" base class ``BaseClassName`` "
""
#: ../../tutorial/classes.rst:612
msgid "Python has two built-in functions that work with inheritance:"
msgstr "Python "
#: ../../tutorial/classes.rst:614
msgid ""
"Use :func:`isinstance` to check an instance's type: ``isinstance(obj, int)`` "
"will be ``True`` only if ``obj.__class__`` is :class:`int` or some class "
"derived from :class:`int`."
msgstr ""
" :func:`isinstance` ``isinstance(obj, int)`` "
"``obj.__class__`` :class:`int` :class:`int` "
"``True``"
#: ../../tutorial/classes.rst:618
msgid ""
"Use :func:`issubclass` to check class inheritance: ``issubclass(bool, int)`` "
"is ``True`` since :class:`bool` is a subclass of :class:`int`. However, "
"``issubclass(float, int)`` is ``False`` since :class:`float` is not a "
"subclass of :class:`int`."
msgstr ""
" :func:`issubclass` class ``issubclass(bool, int)`` "
"``True`` :class:`bool` :class:`int` subclass"
"``issubclass(float, int)`` ``False`` :class:`float` :class:"
"`int` subclass"
#: ../../tutorial/classes.rst:628
msgid "Multiple Inheritance"
msgstr ""
#: ../../tutorial/classes.rst:630
msgid ""
"Python supports a form of multiple inheritance as well. A class definition "
"with multiple base classes looks like this::"
msgstr ""
"Python base class class definition "
" ::"
#: ../../tutorial/classes.rst:633
msgid ""
"class DerivedClassName(Base1, Base2, Base3):\n"
" \n"
" .\n"
" .\n"
" .\n"
" "
msgstr ""
"class DerivedClassName(Base1, Base2, Base3):\n"
" \n"
" .\n"
" .\n"
" .\n"
" "
#: ../../tutorial/classes.rst:640
msgid ""
"For most purposes, in the simplest cases, you can think of the search for "
"attributes inherited from a parent class as depth-first, left-to-right, not "
"searching twice in the same class where there is an overlap in the "
"hierarchy. Thus, if an attribute is not found in :class:`!DerivedClassName`, "
"it is searched for in :class:`!Base1`, then (recursively) in the base "
"classes of :class:`!Base1`, and if it was not found there, it was searched "
"for in :class:`!Base2`, and so on."
msgstr ""
" parent class"
" class "
" :class:`!DerivedClassName` :"
"class:`!Base1` :class:`!Base1` base class "
" :class:`!Base2` "
#: ../../tutorial/classes.rst:647
msgid ""
"In fact, it is slightly more complex than that; the method resolution order "
"changes dynamically to support cooperative calls to :func:`super`. This "
"approach is known in some other multiple-inheritance languages as call-next-"
"method and is more powerful than the super call found in single-inheritance "
"languages."
msgstr ""
"method :func:"
"`super` (call-"
"next-method) super call"
#: ../../tutorial/classes.rst:653
msgid ""
"Dynamic ordering is necessary because all cases of multiple inheritance "
"exhibit one or more diamond relationships (where at least one of the parent "
"classes can be accessed through multiple paths from the bottommost class). "
"For example, all classes inherit from :class:`object`, so any case of "
"multiple inheritance provides more than one path to reach :class:`object`. "
"To keep the base classes from being accessed more than once, the dynamic "
"algorithm linearizes the search order in a way that preserves the left-to-"
"right ordering specified in each class, that calls each parent only once, "
"and that is monotonic (meaning that a class can be subclassed without "
"affecting the precedence order of its parents). Taken together, these "
"properties make it possible to design reliable and extensible classes with "
"multiple inheritance. For more detail, see :ref:`python_2.3_mro`."
msgstr ""
" "
"parent class class class "
" :class:`object` :class:`object` "
" base class "
"(linearize) class parent "
" (monotonic) class subclassed"
" parent "
" class :ref:`python_2.3_mro`"
#: ../../tutorial/classes.rst:670
msgid "Private Variables"
msgstr ""
#: ../../tutorial/classes.rst:672
msgid ""
"\"Private\" instance variables that cannot be accessed except from inside an "
"object don't exist in Python. However, there is a convention that is "
"followed by most Python code: a name prefixed with an underscore (e.g. "
"``_spam``) should be treated as a non-public part of the API (whether it is "
"a function, a method or a data member). It should be considered an "
"implementation detail and subject to change without notice."
msgstr ""
"(private) Python "
" Python "
"``_spam`` API (non-public) "
""
""
#: ../../tutorial/classes.rst:682
msgid ""
"Since there is a valid use-case for class-private members (namely to avoid "
"name clashes of names with names defined by subclasses), there is limited "
"support for such a mechanism, called :dfn:`name mangling`. Any identifier "
"of the form ``__spam`` (at least two leading underscores, at most one "
"trailing underscore) is textually replaced with ``_classname__spam``, where "
"``classname`` is the current class name with leading underscore(s) "
"stripped. This mangling is done without regard to the syntactic position of "
"the identifier, as long as it occurs within the definition of a class."
msgstr ""
" class subclass "
" :dfn:`name mangling`\\ "
" ``__spam``\\ "
" (identifier) ``_classname__spam`` "
"``classname`` class class "
""
#: ../../tutorial/classes.rst:693
msgid ""
"The :ref:`private name mangling specifications ` for "
"details and special cases."
msgstr ""
"\\ :ref:` `\\ "
#: ../../tutorial/classes.rst:696
msgid ""
"Name mangling is helpful for letting subclasses override methods without "
"breaking intraclass method calls. For example::"
msgstr ""
" subclass method class method "
" ::"
#: ../../tutorial/classes.rst:699
msgid ""
"class Mapping:\n"
" def __init__(self, iterable):\n"
" self.items_list = []\n"
" self.__update(iterable)\n"
"\n"
" def update(self, iterable):\n"
" for item in iterable:\n"
" self.items_list.append(item)\n"
"\n"
" __update = update # private copy of original update() method\n"
"\n"
"class MappingSubclass(Mapping):\n"
"\n"
" def update(self, keys, values):\n"
" # provides new signature for update()\n"
" # but does not break __init__()\n"
" for item in zip(keys, values):\n"
" self.items_list.append(item)"
msgstr ""
#: ../../tutorial/classes.rst:718
msgid ""
"The above example would work even if ``MappingSubclass`` were to introduce a "
"``__update`` identifier since it is replaced with ``_Mapping__update`` in "
"the ``Mapping`` class and ``_MappingSubclass__update`` in the "
"``MappingSubclass`` class respectively."
msgstr ""
" ``MappingSubclass`` ``__update`` "
" ``Mapping`` class ``_Mapping__update`` "
"``MappingSubclass`` class ``_MappingSubclass__update``"
#: ../../tutorial/classes.rst:723
msgid ""
"Note that the mangling rules are designed mostly to avoid accidents; it "
"still is possible to access or modify a variable that is considered "
"private. This can even be useful in special circumstances, such as in the "
"debugger."
msgstr ""
""
" (debugger)"
#: ../../tutorial/classes.rst:727
msgid ""
"Notice that code passed to ``exec()`` or ``eval()`` does not consider the "
"classname of the invoking class to be the current class; this is similar to "
"the effect of the ``global`` statement, the effect of which is likewise "
"restricted to code that is byte-compiled together. The same restriction "
"applies to ``getattr()``, ``setattr()`` and ``delattr()``, as well as when "
"referencing ``__dict__`` directly."
msgstr ""
" ``exec()`` ``eval()`` class "
" class ``global`` "
" (byte-compiled) ``getattr()``"
"``setattr()`` ``delattr()`` ``__dict__`` "
#: ../../tutorial/classes.rst:738
msgid "Odds and Ends"
msgstr ""
#: ../../tutorial/classes.rst:740
msgid ""
"Sometimes it is useful to have a data type similar to the Pascal \"record\" "
"or C \"struct\", bundling together a few named data items. The idiomatic "
"approach is to use :mod:`dataclasses` for this purpose::"
msgstr ""
" Pascal record C struct"
" :mod:"
"`dataclasses` ::"
#: ../../tutorial/classes.rst:744
msgid ""
"from dataclasses import dataclass\n"
"\n"
"@dataclass\n"
"class Employee:\n"
" name: str\n"
" dept: str\n"
" salary: int"
msgstr ""
"from dataclasses import dataclass\n"
"\n"
"@dataclass\n"
"class Employee:\n"
" name: str\n"
" dept: str\n"
" salary: int"
#: ../../tutorial/classes.rst:754
msgid ""
">>> john = Employee('john', 'computer lab', 1000)\n"
">>> john.dept\n"
"'computer lab'\n"
">>> john.salary\n"
"1000"
msgstr ""
">>> john = Employee('john', 'computer lab', 1000)\n"
">>> john.dept\n"
"'computer lab'\n"
">>> john.salary\n"
"1000"
#: ../../tutorial/classes.rst:760
msgid ""
"A piece of Python code that expects a particular abstract data type can "
"often be passed a class that emulates the methods of that data type "
"instead. For instance, if you have a function that formats some data from a "
"file object, you can define a class with methods :meth:`~io.TextIOBase.read` "
"and :meth:`~io.TextIOBase.readline` that get the data from a string buffer "
"instead, and pass it as an argument."
msgstr ""
" Python class "
" class method"
" :meth:`~io.TextIOBase.read` :"
"meth:`~io.TextIOBase.readline` method class "
""
#: ../../tutorial/classes.rst:772
msgid ""
":ref:`Instance method objects ` have attributes, too: :"
"attr:`m.__self__ ` is the instance object with the method :"
"meth:`!m`, and :attr:`m.__func__ ` is the :ref:`function "
"object ` corresponding to the method."
msgstr ""
":ref:` method `\\ :attr:`m.__self__ "
"` method :meth:`!m` :attr:`m."
"__func__ ` method \\ :ref:` `"
#: ../../tutorial/classes.rst:782
msgid "Iterators"
msgstr " (Iterator)"
#: ../../tutorial/classes.rst:784
msgid ""
"By now you have probably noticed that most container objects can be looped "
"over using a :keyword:`for` statement::"
msgstr ""
" (container) :keyword:"
"`for` ::"
#: ../../tutorial/classes.rst:787
msgid ""
"for element in [1, 2, 3]:\n"
" print(element)\n"
"for element in (1, 2, 3):\n"
" print(element)\n"
"for key in {'one':1, 'two':2}:\n"
" print(key)\n"
"for char in \"123\":\n"
" print(char)\n"
"for line in open(\"myfile.txt\"):\n"
" print(line, end='')"
msgstr ""
"for element in [1, 2, 3]:\n"
" print(element)\n"
"for element in (1, 2, 3):\n"
" print(element)\n"
"for key in {'one':1, 'two':2}:\n"
" print(key)\n"
"for char in \"123\":\n"
" print(char)\n"
"for line in open(\"myfile.txt\"):\n"
" print(line, end='')"
#: ../../tutorial/classes.rst:798
msgid ""
"This style of access is clear, concise, and convenient. The use of "
"iterators pervades and unifies Python. Behind the scenes, the :keyword:"
"`for` statement calls :func:`iter` on the container object. The function "
"returns an iterator object that defines the method :meth:`~iterator."
"__next__` which accesses elements in the container one at a time. When "
"there are no more elements, :meth:`~iterator.__next__` raises a :exc:"
"`StopIteration` exception which tells the :keyword:`!for` loop to "
"terminate. You can call the :meth:`~iterator.__next__` method using the :"
"func:`next` built-in function; this example shows how it all works::"
msgstr ""
" Python "
":keyword:`for` :func:`iter`"
" :meth:`~iterator.__next__` method method "
":meth:`~iterator.__next__` :exc:"
"`StopIteration` :keyword:`!for` :"
"func:`next` :meth:`~iterator.__next__` method"
" ::"
#: ../../tutorial/classes.rst:807
msgid ""
">>> s = 'abc'\n"
">>> it = iter(s)\n"
">>> it\n"
"\n"
">>> next(it)\n"
"'a'\n"
">>> next(it)\n"
"'b'\n"
">>> next(it)\n"
"'c'\n"
">>> next(it)\n"
"Traceback (most recent call last):\n"
" File \"\", line 1, in \n"
" next(it)\n"
"StopIteration"
msgstr ""
">>> s = 'abc'\n"
">>> it = iter(s)\n"
">>> it\n"
"\n"
">>> next(it)\n"
"'a'\n"
">>> next(it)\n"
"'b'\n"
">>> next(it)\n"
"'c'\n"
">>> next(it)\n"
"Traceback (most recent call last):\n"
" File \"\", line 1, in \n"
" next(it)\n"
"StopIteration"
#: ../../tutorial/classes.rst:823
msgid ""
"Having seen the mechanics behind the iterator protocol, it is easy to add "
"iterator behavior to your classes. Define an :meth:`~container.__iter__` "
"method which returns an object with a :meth:`~iterator.__next__` method. If "
"the class defines :meth:`!__next__`, then :meth:`!__iter__` can just return "
"``self``::"
msgstr ""
" class "
" :meth:`~container.__iter__` method :meth:`~iterator."
"__next__` method class :meth:`!__next__` :meth:`!"
"__iter__` ``self`` ::"
#: ../../tutorial/classes.rst:828
msgid ""
"class Reverse:\n"
" \"\"\"Iterator for looping over a sequence backwards.\"\"\"\n"
" def __init__(self, data):\n"
" self.data = data\n"
" self.index = len(data)\n"
"\n"
" def __iter__(self):\n"
" return self\n"
"\n"
" def __next__(self):\n"
" if self.index == 0:\n"
" raise StopIteration\n"
" self.index = self.index - 1\n"
" return self.data[self.index]"
msgstr ""
#: ../../tutorial/classes.rst:845
msgid ""
">>> rev = Reverse('spam')\n"
">>> iter(rev)\n"
"\n"
">>> for char in rev:\n"
"... print(char)\n"
"...\n"
"m\n"
"a\n"
"p\n"
"s"
msgstr ""
">>> rev = Reverse('spam')\n"
">>> iter(rev)\n"
"\n"
">>> for char in rev:\n"
"... print(char)\n"
"...\n"
"m\n"
"a\n"
"p\n"
"s"
#: ../../tutorial/classes.rst:860
msgid "Generators"
msgstr " (Generator)"
#: ../../tutorial/classes.rst:862
msgid ""
":term:`Generators ` are a simple and powerful tool for creating "
"iterators. They are written like regular functions but use the :keyword:"
"`yield` statement whenever they want to return data. Each time :func:`next` "
"is called on it, the generator resumes where it left off (it remembers all "
"the data values and which statement was last executed). An example shows "
"that generators can be trivially easy to create::"
msgstr ""
":term:` `\\ "
" :keyword:`yield` "
" :func:`next` "
" ::"
#: ../../tutorial/classes.rst:869
msgid ""
"def reverse(data):\n"
" for index in range(len(data)-1, -1, -1):\n"
" yield data[index]"
msgstr ""
"def reverse(data):\n"
" for index in range(len(data)-1, -1, -1):\n"
" yield data[index]"
#: ../../tutorial/classes.rst:875
msgid ""
">>> for char in reverse('golf'):\n"
"... print(char)\n"
"...\n"
"f\n"
"l\n"
"o\n"
"g"
msgstr ""
">>> for char in reverse('golf'):\n"
"... print(char)\n"
"...\n"
"f\n"
"l\n"
"o\n"
"g"
#: ../../tutorial/classes.rst:883
msgid ""
"Anything that can be done with generators can also be done with class-based "
"iterators as described in the previous section. What makes generators so "
"compact is that the :meth:`~iterator.__iter__` and :meth:`~generator."
"__next__` methods are created automatically."
msgstr ""
" class "
":meth:`~iterator.__iter__` :"
"meth:`~generator.__next__` method "
#: ../../tutorial/classes.rst:888
msgid ""
"Another key feature is that the local variables and execution state are "
"automatically saved between calls. This made the function easier to write "
"and much more clear than an approach using instance variables like ``self."
"index`` and ``self.data``."
msgstr ""
""
" ``self.index`` ``self.data`` "
""
#: ../../tutorial/classes.rst:893
msgid ""
"In addition to automatic method creation and saving program state, when "
"generators terminate, they automatically raise :exc:`StopIteration`. In "
"combination, these features make it easy to create iterators with no more "
"effort than writing a regular function."
msgstr ""
" method :exc:"
"`StopIteration`"
#: ../../tutorial/classes.rst:902
msgid "Generator Expressions"
msgstr ""
#: ../../tutorial/classes.rst:904
msgid ""
"Some simple generators can be coded succinctly as expressions using a syntax "
"similar to list comprehensions but with parentheses instead of square "
"brackets. These expressions are designed for situations where the generator "
"is used right away by an enclosing function. Generator expressions are more "
"compact but less versatile than full generator definitions and tend to be "
"more memory friendly than equivalent list comprehensions."
msgstr ""
" list "
"comprehension"
" (enclosing function) "
" list comprehension "
""
#: ../../tutorial/classes.rst:911
msgid "Examples::"
msgstr " ::"
#: ../../tutorial/classes.rst:913
msgid ""
">>> sum(i*i for i in range(10)) # sum of squares\n"
"285\n"
"\n"
">>> xvec = [10, 20, 30]\n"
">>> yvec = [7, 5, 3]\n"
">>> sum(x*y for x,y in zip(xvec, yvec)) # dot product\n"
"260\n"
"\n"
">>> unique_words = set(word for line in page for word in line.split())\n"
"\n"
">>> valedictorian = max((student.gpa, student.name) for student in "
"graduates)\n"
"\n"
">>> data = 'golf'\n"
">>> list(data[i] for i in range(len(data)-1, -1, -1))\n"
"['f', 'l', 'o', 'g']"
msgstr ""
#: ../../tutorial/classes.rst:932
msgid "Footnotes"
msgstr ""
#: ../../tutorial/classes.rst:933
msgid ""
"Except for one thing. Module objects have a secret read-only attribute "
"called :attr:`~object.__dict__` which returns the dictionary used to "
"implement the module's namespace; the name :attr:`~object.__dict__` is an "
"attribute but not a global name. Obviously, using this violates the "
"abstraction of namespace implementation, and should be restricted to things "
"like post-mortem debuggers."
msgstr ""
" :attr:`~object.__dict__`"
" dictionary:attr:`~object.__dict__` "
""
" (post-mortem debugger) "
#: ../../tutorial/classes.rst:343
msgid "object"
msgstr "object"
#: ../../tutorial/classes.rst:343
msgid "method"
msgstr "method"
#: ../../tutorial/classes.rst:679
msgid "name"
msgstr "name"
#: ../../tutorial/classes.rst:679
msgid "mangling"
msgstr "mangling"
#~ msgid ""
#~ "The other kind of instance attribute reference is a *method*. A method is "
#~ "a function that \"belongs to\" an object. (In Python, the term method is "
#~ "not unique to class instances: other object types can have methods as "
#~ "well. For example, list objects have methods called append, insert, "
#~ "remove, sort, and so on. However, in the following discussion, we'll use "
#~ "the term method exclusively to mean methods of class instance objects, "
#~ "unless explicitly stated otherwise.)"
#~ msgstr ""
#~ " *method*Method "
#~ "Python method class "
#~ "methodlist appendinsertremovesort method"
#~ " method class "
#~ "method"