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#
SOME DESCRIPTIVE TITLE.
#
Copyright (C) 2001-2022, Python Software Foundation
#
This file is distributed under the same license as the Python package.
#
#
Translators:
msgid ""
msgstr ""
"
Project-Id-Version
:
Python 3.13\n
"
"
Report-Msgid-Bugs-To
:
\n
"
"
POT-Creation-Date
:
2025-06-27 07:36+0000\n
"
"
PO-Revision-Date
:
2018-05-23 16:17+0000\n
"
"
Last-Translator
:
Adrian Liaw <adrianliaw2000@gmail.com>\n
"
"
Language-Team
:
Chinese - TAIWAN (https://github.com/python/python-docs-zh-
"
"
tw)\n
"
"
Language
:
zh_TW\n
"
"
MIME-Version
:
1.0\n
"
"
Content-Type
:
text/plain; charset=UTF-8\n
"
"
Content-Transfer-Encoding
:
8bit\n
"
"
Plural-Forms
:
nplurals=1; plural=0;\n
"
#:
../../reference/expressions.rst:6
msgid
"Expressions"
msgstr
"運算式"
#:
../../reference/expressions.rst:10
msgid
""
"This chapter explains the meaning of the elements of expressions in Python."
msgstr
""
#:
../../reference/expressions.rst:12
msgid
""
"**Syntax Notes:** In this and the following chapters, extended BNF notation "
"will be used to describe syntax, not lexical analysis. When (one "
"alternative of) a syntax rule has the form"
msgstr
""
#:
../../reference/expressions.rst:19
msgid
""
"and no semantics are given, the semantics of this form of ``name`` are the "
"same as for ``othername``."
msgstr
""
#:
../../reference/expressions.rst:26
msgid
"Arithmetic conversions"
msgstr
""
#:
../../reference/expressions.rst:30
msgid
""
"When a description of an arithmetic operator below uses the phrase
\"
the "
"numeric arguments are converted to a common type
\"
, this means that the "
"operator implementation for built-in types works as follows:"
msgstr
""
#:
../../reference/expressions.rst:34
msgid
""
"If either argument is a complex number, the other is converted to complex;"
msgstr
""
#:
../../reference/expressions.rst:36
msgid
""
"otherwise, if either argument is a floating-point number, the other is "
"converted to floating point;"
msgstr
""
#:
../../reference/expressions.rst:39
msgid
"otherwise, both must be integers and no conversion is necessary."
msgstr
""
#:
../../reference/expressions.rst:41
msgid
""
"Some additional rules apply for certain operators (e.g., a string as a left "
"argument to the '%' operator). Extensions must define their own conversion "
"behavior."
msgstr
""
#:
../../reference/expressions.rst:49
msgid
"Atoms"
msgstr
""
#:
../../reference/expressions.rst:53
msgid
""
"Atoms are the most basic elements of expressions. The simplest atoms are "
"identifiers or literals. Forms enclosed in parentheses, brackets or braces "
"are also categorized syntactically as atoms. The syntax for atoms is:"
msgstr
""
#:
../../reference/expressions.rst:66
msgid
"Identifiers (Names)"
msgstr
""
#:
../../reference/expressions.rst:70
msgid
""
"An identifier occurring as an atom is a name. See section :ref:"
"`identifiers` for lexical definition and section :ref:`naming` for "
"documentation of naming and binding."
msgstr
""
#:
../../reference/expressions.rst:76
msgid
""
"When the name is bound to an object, evaluation of the atom yields that "
"object. When a name is not bound, an attempt to evaluate it raises a :exc:"
"`NameError` exception."
msgstr
""
#:
../../reference/expressions.rst:87
msgid
"Private name mangling"
msgstr
""
#:
../../reference/expressions.rst:89
msgid
""
"When an identifier that textually occurs in a class definition begins with "
"two or more underscore characters and does not end in two or more "
"underscores, it is considered a :dfn:`private name` of that class."
msgstr
""
#:
../../reference/expressions.rst:95
msgid
"The :ref:`class specifications <class>`."
msgstr
""
#:
../../reference/expressions.rst:97
msgid
""
"More precisely, private names are transformed to a longer form before code "
"is generated for them. If the transformed name is longer than 255 "
"characters, implementation-defined truncation may happen."
msgstr
""
#:
../../reference/expressions.rst:101
msgid
""
"The transformation is independent of the syntactical context in which the "
"identifier is used but only the following private identifiers are mangled:"
msgstr
""
#:
../../reference/expressions.rst:104
msgid
""
"Any name used as the name of a variable that is assigned or read or any name "
"of an attribute being accessed."
msgstr
""
#:
../../reference/expressions.rst:107
msgid
""
"The :attr:`~definition.__name__` attribute of nested functions, classes, and "
"type aliases is however not mangled."
msgstr
""
#:
../../reference/expressions.rst:110
msgid
""
"The name of imported modules, e.g., ``__spam`` in ``import __spam``. If the "
"module is part of a package (i.e., its name contains a dot), the name is "
"*not* mangled, e.g., the ``__foo`` in ``import __foo.bar`` is not mangled."
msgstr
""
#:
../../reference/expressions.rst:115
msgid
""
"The name of an imported member, e.g., ``__f`` in ``from spam import __f``."
msgstr
""
#:
../../reference/expressions.rst:117
msgid
"The transformation rule is defined as follows:"
msgstr
""
#:
../../reference/expressions.rst:119
msgid
""
"The class name, with leading underscores removed and a single leading "
"underscore inserted, is inserted in front of the identifier, e.g., the "
"identifier ``__spam`` occurring in a class named ``Foo``, ``_Foo`` or "
"``__Foo`` is transformed to ``_Foo__spam``."
msgstr
""
#:
../../reference/expressions.rst:124
msgid
""
"If the class name consists only of underscores, the transformation is the "
"identity, e.g., the identifier ``__spam`` occurring in a class named ``_`` "
"or ``__`` is left as is."
msgstr
""
#:
../../reference/expressions.rst:131
msgid
"Literals"
msgstr
""
#:
../../reference/expressions.rst:135
msgid
"Python supports string and bytes literals and various numeric literals:"
msgstr
""
#:
../../reference/expressions.rst:141
msgid
""
"Evaluation of a literal yields an object of the given type (string, bytes, "
"integer, floating-point number, complex number) with the given value. The "
"value may be approximated in the case of floating-point and imaginary "
"(complex) literals. See section :ref:`literals` for details."
msgstr
""
#:
../../reference/expressions.rst:150
msgid
""
"All literals correspond to immutable data types, and hence the object's "
"identity is less important than its value. Multiple evaluations of literals "
"with the same value (either the same occurrence in the program text or a "
"different occurrence) may obtain the same object or a different object with "
"the same value."
msgstr
""
#:
../../reference/expressions.rst:160
msgid
"Parenthesized forms"
msgstr
""
#:
../../reference/expressions.rst:166
msgid
""
"A parenthesized form is an optional expression list enclosed in parentheses:"
msgstr
""
#:
../../reference/expressions.rst:171
msgid
""
"A parenthesized expression list yields whatever that expression list yields: "
"if the list contains at least one comma, it yields a tuple; otherwise, it "
"yields the single expression that makes up the expression list."
msgstr
""
#:
../../reference/expressions.rst:177
msgid
""
"An empty pair of parentheses yields an empty tuple object. Since tuples are "
"immutable, the same rules as for literals apply (i.e., two occurrences of "
"the empty tuple may or may not yield the same object)."
msgstr
""
#:
../../reference/expressions.rst:185
msgid
""
"Note that tuples are not formed by the parentheses, but rather by use of the "
"comma. The exception is the empty tuple, for which parentheses *are* "
"required --- allowing unparenthesized
\"
nothing
\"
in expressions would cause "
"ambiguities and allow common typos to pass uncaught."
msgstr
""
#:
../../reference/expressions.rst:194
msgid
"Displays for lists, sets and dictionaries"
msgstr
""
#:
../../reference/expressions.rst:198
msgid
""
"For constructing a list, a set or a dictionary Python provides special "
"syntax called
\"
displays
\"
, each of them in two flavors:"
msgstr
""
#:
../../reference/expressions.rst:201
msgid
"either the container contents are listed explicitly, or"
msgstr
""
#:
../../reference/expressions.rst:203
msgid
""
"they are computed via a set of looping and filtering instructions, called a :"
"dfn:`comprehension`."
msgstr
""
#:
../../reference/expressions.rst:211
msgid
"Common syntax elements for comprehensions are:"
msgstr
""
#:
../../reference/expressions.rst:219
msgid
""
"The comprehension consists of a single expression followed by at least one :"
"keyword:`!for` clause and zero or more :keyword:`!for` or :keyword:`!if` "
"clauses. In this case, the elements of the new container are those that "
"would be produced by considering each of the :keyword:`!for` or :keyword:`!"
"if` clauses a block, nesting from left to right, and evaluating the "
"expression to produce an element each time the innermost block is reached."
msgstr
""
#:
../../reference/expressions.rst:226
msgid
""
"However, aside from the iterable expression in the leftmost :keyword:`!for` "
"clause, the comprehension is executed in a separate implicitly nested scope. "
"This ensures that names assigned to in the target list don't
\"
leak
\"
into "
"the enclosing scope."
msgstr
""
#:
../../reference/expressions.rst:230
msgid
""
"The iterable expression in the leftmost :keyword:`!for` clause is evaluated "
"directly in the enclosing scope and then passed as an argument to the "
"implicitly nested scope. Subsequent :keyword:`!for` clauses and any filter "
"condition in the leftmost :keyword:`!for` clause cannot be evaluated in the "
"enclosing scope as they may depend on the values obtained from the leftmost "
"iterable. For example: ``[x*y for x in range(10) for y in range(x, x+10)]``."
msgstr
""
#:
../../reference/expressions.rst:237
msgid
""
"To ensure the comprehension always results in a container of the appropriate "
"type, ``yield`` and ``yield from`` expressions are prohibited in the "
"implicitly nested scope."
msgstr
""
#:
../../reference/expressions.rst:244
msgid
""
"Since Python 3.6, in an :keyword:`async def` function, an :keyword:`!async "
"for` clause may be used to iterate over a :term:`asynchronous iterator`. A "
"comprehension in an :keyword:`!async def` function may consist of either a :"
"keyword:`!for` or :keyword:`!async for` clause following the leading "
"expression, may contain additional :keyword:`!for` or :keyword:`!async for` "
"clauses, and may also use :keyword:`await` expressions."
msgstr
""
#:
../../reference/expressions.rst:251
msgid
""
"If a comprehension contains :keyword:`!async for` clauses, or if it "
"contains :keyword:`!await` expressions or other asynchronous comprehensions "
"anywhere except the iterable expression in the leftmost :keyword:`!for` "
"clause, it is called an :dfn:`asynchronous comprehension`. An asynchronous "
"comprehension may suspend the execution of the coroutine function in which "
"it appears. See also :pep:`530`."
msgstr
""
#:
../../reference/expressions.rst:258
msgid
"Asynchronous comprehensions were introduced."
msgstr
""
#:
../../reference/expressions.rst:261
../../reference/expressions.rst:440
msgid
"``yield`` and ``yield from`` prohibited in the implicitly nested scope."
msgstr
""
#:
../../reference/expressions.rst:264
msgid
""
"Asynchronous comprehensions are now allowed inside comprehensions in "
"asynchronous functions. Outer comprehensions implicitly become asynchronous."
msgstr
""
#:
../../reference/expressions.rst:273
msgid
"List displays"
msgstr
""
#:
../../reference/expressions.rst:283
msgid
""
"A list display is a possibly empty series of expressions enclosed in square "
"brackets:"
msgstr
""
#:
../../reference/expressions.rst:289
msgid
""
"A list display yields a new list object, the contents being specified by "
"either a list of expressions or a comprehension. When a comma-separated "
"list of expressions is supplied, its elements are evaluated from left to "
"right and placed into the list object in that order. When a comprehension "
"is supplied, the list is constructed from the elements resulting from the "
"comprehension."
msgstr
""
#:
../../reference/expressions.rst:299
msgid
"Set displays"
msgstr
""
#:
../../reference/expressions.rst:308
msgid
""
"A set display is denoted by curly braces and distinguishable from dictionary "
"displays by the lack of colons separating keys and values:"
msgstr
""
#:
../../reference/expressions.rst:314
msgid
""
"A set display yields a new mutable set object, the contents being specified "
"by either a sequence of expressions or a comprehension. When a comma-"
"separated list of expressions is supplied, its elements are evaluated from "
"left to right and added to the set object. When a comprehension is "
"supplied, the set is constructed from the elements resulting from the "
"comprehension."
msgstr
""
#:
../../reference/expressions.rst:320
msgid
""
"An empty set cannot be constructed with ``{}``; this literal constructs an "
"empty dictionary."
msgstr
""
#:
../../reference/expressions.rst:327
msgid
"Dictionary displays"
msgstr
""
#:
../../reference/expressions.rst:338
msgid
""
"A dictionary display is a possibly empty series of dict items (key/value "
"pairs) enclosed in curly braces:"
msgstr
""
#:
../../reference/expressions.rst:347
msgid
"A dictionary display yields a new dictionary object."
msgstr
""
#:
../../reference/expressions.rst:349
msgid
""
"If a comma-separated sequence of dict items is given, they are evaluated "
"from left to right to define the entries of the dictionary: each key object "
"is used as a key into the dictionary to store the corresponding value. This "
"means that you can specify the same key multiple times in the dict item "
"list, and the final dictionary's value for that key will be the last one "
"given."
msgstr
""
#:
../../reference/expressions.rst:359
msgid
""
"A double asterisk ``**`` denotes :dfn:`dictionary unpacking`. Its operand "
"must be a :term:`mapping`. Each mapping item is added to the new "
"dictionary. Later values replace values already set by earlier dict items "
"and earlier dictionary unpackings."
msgstr
""
#:
../../reference/expressions.rst:364
msgid
"Unpacking into dictionary displays, originally proposed by :pep:`448`."
msgstr
""
#:
../../reference/expressions.rst:367
msgid
""
"A dict comprehension, in contrast to list and set comprehensions, needs two "
"expressions separated with a colon followed by the usual
\"
for
\"
and
\"
if
\"
"
"clauses. When the comprehension is run, the resulting key and value elements "
"are inserted in the new dictionary in the order they are produced."
msgstr
""
#:
../../reference/expressions.rst:375
msgid
""
"Restrictions on the types of the key values are listed earlier in section :"
"ref:`types`. (To summarize, the key type should be :term:`hashable`, which "
"excludes all mutable objects.) Clashes between duplicate keys are not "
"detected; the last value (textually rightmost in the display) stored for a "
"given key value prevails."
msgstr
""
#:
../../reference/expressions.rst:381
msgid
""
"Prior to Python 3.8, in dict comprehensions, the evaluation order of key and "
"value was not well-defined. In CPython, the value was evaluated before the "
"key. Starting with 3.8, the key is evaluated before the value, as proposed "
"by :pep:`572`."
msgstr
""
#:
../../reference/expressions.rst:391
msgid
"Generator expressions"
msgstr
""
#:
../../reference/expressions.rst:398
msgid
"A generator expression is a compact generator notation in parentheses:"
msgstr
""
#:
../../reference/expressions.rst:403
msgid
""
"A generator expression yields a new generator object. Its syntax is the "
"same as for comprehensions, except that it is enclosed in parentheses "
"instead of brackets or curly braces."
msgstr
""
#:
../../reference/expressions.rst:407
msgid
""
"Variables used in the generator expression are evaluated lazily when the :"
"meth:`~generator.__next__` method is called for the generator object (in the "
"same fashion as normal generators). However, the iterable expression in the "
"leftmost :keyword:`!for` clause is immediately evaluated, and the :term:"
"`iterator` is immediately created for that iterable, so that an error "
"produced while creating the iterator will be emitted at the point where the "
"generator expression is defined, rather than at the point where the first "
"value is retrieved. Subsequent :keyword:`!for` clauses and any filter "
"condition in the leftmost :keyword:`!for` clause cannot be evaluated in the "
"enclosing scope as they may depend on the values obtained from the leftmost "
"iterable. For example: ``(x*y for x in range(10) for y in range(x, x+10))``."
msgstr
""
#:
../../reference/expressions.rst:419
msgid
""
"The parentheses can be omitted on calls with only one argument. See "
"section :ref:`calls` for details."
msgstr
""
#:
../../reference/expressions.rst:422
msgid
""
"To avoid interfering with the expected operation of the generator expression "
"itself, ``yield`` and ``yield from`` expressions are prohibited in the "
"implicitly defined generator."
msgstr
""
#:
../../reference/expressions.rst:426
msgid
""
"If a generator expression contains either :keyword:`!async for` clauses or :"
"keyword:`await` expressions it is called an :dfn:`asynchronous generator "
"expression`. An asynchronous generator expression returns a new "
"asynchronous generator object, which is an asynchronous iterator (see :ref:"
"`async-iterators`)."
msgstr
""
#:
../../reference/expressions.rst:432
msgid
"Asynchronous generator expressions were introduced."
msgstr
""
#:
../../reference/expressions.rst:435
msgid
""
"Prior to Python 3.7, asynchronous generator expressions could only appear "
"in :keyword:`async def` coroutines. Starting with 3.7, any function can use "
"asynchronous generator expressions."
msgstr
""
#:
../../reference/expressions.rst:447
msgid
"Yield expressions"
msgstr
""
#:
../../reference/expressions.rst:460
msgid
""
"The yield expression is used when defining a :term:`generator` function or "
"an :term:`asynchronous generator` function and thus can only be used in the "
"body of a function definition. Using a yield expression in a function's "
"body causes that function to be a generator function, and using it in an :"
"keyword:`async def` function's body causes that coroutine function to be an "
"asynchronous generator function. For example::"
msgstr
""
#:
../../reference/expressions.rst:467
msgid
""
"def gen(): # defines a generator function\n"
" yield 123\n"
"\n"
"async def agen(): # defines an asynchronous generator function\n"
" yield 123"
msgstr
""
#:
../../reference/expressions.rst:473
msgid
""
"Due to their side effects on the containing scope, ``yield`` expressions are "
"not permitted as part of the implicitly defined scopes used to implement "
"comprehensions and generator expressions."
msgstr
""
#:
../../reference/expressions.rst:477
msgid
""
"Yield expressions prohibited in the implicitly nested scopes used to "
"implement comprehensions and generator expressions."
msgstr
""
#:
../../reference/expressions.rst:481
msgid
""
"Generator functions are described below, while asynchronous generator "
"functions are described separately in section :ref:`asynchronous-generator-"
"functions`."
msgstr
""
#:
../../reference/expressions.rst:485
msgid
""
"When a generator function is called, it returns an iterator known as a "
"generator. That generator then controls the execution of the generator "
"function. The execution starts when one of the generator's methods is "
"called. At that time, the execution proceeds to the first yield expression, "
"where it is suspended again, returning the value of :token:`~python-grammar:"
"yield_list` to the generator's caller, or ``None`` if :token:`~python-"
"grammar:yield_list` is omitted. By suspended, we mean that all local state "
"is retained, including the current bindings of local variables, the "
"instruction pointer, the internal evaluation stack, and the state of any "
"exception handling. When the execution is resumed by calling one of the "
"generator's methods, the function can proceed exactly as if the yield "
"expression were just another external call. The value of the yield "
"expression after resuming depends on the method which resumed the "
"execution. If :meth:`~generator.__next__` is used (typically via either a :"
"keyword:`for` or the :func:`next` builtin) then the result is :const:"
"`None`. Otherwise, if :meth:`~generator.send` is used, then the result will "
"be the value passed in to that method."
msgstr
""
#:
../../reference/expressions.rst:505
msgid
""
"All of this makes generator functions quite similar to coroutines; they "
"yield multiple times, they have more than one entry point and their "
"execution can be suspended. The only difference is that a generator "
"function cannot control where the execution should continue after it yields; "
"the control is always transferred to the generator's caller."
msgstr
""
#:
../../reference/expressions.rst:511
msgid
""
"Yield expressions are allowed anywhere in a :keyword:`try` construct. If "
"the generator is not resumed before it is finalized (by reaching a zero "
"reference count or by being garbage collected), the generator-iterator's :"
"meth:`~generator.close` method will be called, allowing any pending :keyword:"
"`finally` clauses to execute."
msgstr
""
#:
../../reference/expressions.rst:520
msgid
""
"When ``yield from <expr>`` is used, the supplied expression must be an "
"iterable. The values produced by iterating that iterable are passed directly "
"to the caller of the current generator's methods. Any values passed in with :"
"meth:`~generator.send` and any exceptions passed in with :meth:`~generator."
"throw` are passed to the underlying iterator if it has the appropriate "
"methods. If this is not the case, then :meth:`~generator.send` will raise :"
"exc:`AttributeError` or :exc:`TypeError`, while :meth:`~generator.throw` "
"will just raise the passed in exception immediately."
msgstr
""
#:
../../reference/expressions.rst:529
msgid
""
"When the underlying iterator is complete, the :attr:`~StopIteration.value` "
"attribute of the raised :exc:`StopIteration` instance becomes the value of "
"the yield expression. It can be either set explicitly when raising :exc:"
"`StopIteration`, or automatically when the subiterator is a generator (by "
"returning a value from the subgenerator)."
msgstr
""
#:
../../reference/expressions.rst:535
msgid
"Added ``yield from <expr>`` to delegate control flow to a subiterator."
msgstr
""
#:
../../reference/expressions.rst:538
msgid
""
"The parentheses may be omitted when the yield expression is the sole "
"expression on the right hand side of an assignment statement."
msgstr
""
#:
../../reference/expressions.rst:543
msgid
":pep:`255` - Simple Generators"
msgstr
""
#:
../../reference/expressions.rst:544
msgid
""
"The proposal for adding generators and the :keyword:`yield` statement to "
"Python."
msgstr
""
#:
../../reference/expressions.rst:546
msgid
":pep:`342` - Coroutines via Enhanced Generators"
msgstr
""
#:
../../reference/expressions.rst:547
msgid
""
"The proposal to enhance the API and syntax of generators, making them usable "
"as simple coroutines."
msgstr
""
#:
../../reference/expressions.rst:550
msgid
":pep:`380` - Syntax for Delegating to a Subgenerator"
msgstr
""
#:
../../reference/expressions.rst:551
msgid
""
"The proposal to introduce the :token:`~python-grammar:yield_from` syntax, "
"making delegation to subgenerators easy."
msgstr
""
#:
../../reference/expressions.rst:554
msgid
":pep:`525` - Asynchronous Generators"
msgstr
""
#:
../../reference/expressions.rst:555
msgid
""
"The proposal that expanded on :pep:`492` by adding generator capabilities to "
"coroutine functions."
msgstr
""
#:
../../reference/expressions.rst:562
msgid
"Generator-iterator methods"
msgstr
""
#:
../../reference/expressions.rst:564
msgid
""
"This subsection describes the methods of a generator iterator. They can be "
"used to control the execution of a generator function."
msgstr
""
#:
../../reference/expressions.rst:567
msgid
""
"Note that calling any of the generator methods below when the generator is "
"already executing raises a :exc:`ValueError` exception."
msgstr
""
#:
../../reference/expressions.rst:575
msgid
""
"Starts the execution of a generator function or resumes it at the last "
"executed yield expression. When a generator function is resumed with a :"
"meth:`~generator.__next__` method, the current yield expression always "
"evaluates to :const:`None`. The execution then continues to the next yield "
"expression, where the generator is suspended again, and the value of the :"
"token:`~python-grammar:yield_list` is returned to :meth:`__next__`'s "
"caller. If the generator exits without yielding another value, a :exc:"
"`StopIteration` exception is raised."
msgstr
""
#:
../../reference/expressions.rst:584
msgid
""
"This method is normally called implicitly, e.g. by a :keyword:`for` loop, or "
"by the built-in :func:`next` function."
msgstr
""
#:
../../reference/expressions.rst:590
msgid
""
"Resumes the execution and
\"
sends
\"
a value into the generator function. "
"The *value* argument becomes the result of the current yield expression. "
"The :meth:`send` method returns the next value yielded by the generator, or "
"raises :exc:`StopIteration` if the generator exits without yielding another "
"value. When :meth:`send` is called to start the generator, it must be "
"called with :const:`None` as the argument, because there is no yield "
"expression that could receive the value."
msgstr
""
#:
../../reference/expressions.rst:602
msgid
""
"Raises an exception at the point where the generator was paused, and returns "
"the next value yielded by the generator function. If the generator exits "
"without yielding another value, a :exc:`StopIteration` exception is raised. "
"If the generator function does not catch the passed-in exception, or raises "
"a different exception, then that exception propagates to the caller."
msgstr
""
#:
../../reference/expressions.rst:608
msgid
""
"In typical use, this is called with a single exception instance similar to "
"the way the :keyword:`raise` keyword is used."
msgstr
""
#:
../../reference/expressions.rst:611
msgid
""
"For backwards compatibility, however, the second signature is supported, "
"following a convention from older versions of Python. The *type* argument "
"should be an exception class, and *value* should be an exception instance. "
"If the *value* is not provided, the *type* constructor is called to get an "
"instance. If *traceback* is provided, it is set on the exception, otherwise "
"any existing :attr:`~BaseException.__traceback__` attribute stored in "
"*value* may be cleared."
msgstr
""
#:
../../reference/expressions.rst:622
../../reference/expressions.rst:808
msgid
""
"The second signature
\\
(type
\\
[, value
\\
[, traceback
\\
]
\\
]
\\
) is deprecated "
"and may be removed in a future version of Python."
msgstr
""
#:
../../reference/expressions.rst:630
msgid
""
"Raises a :exc:`GeneratorExit` exception at the point where the generator "
"function was paused (equivalent to calling ``throw(GeneratorExit)``). The "
"exception is raised by the yield expression where the generator was paused. "
"If the generator function catches the exception and returns a value, this "
"value is returned from :meth:`close`. If the generator function is already "
"closed, or raises :exc:`GeneratorExit` (by not catching the exception), :"
"meth:`close` returns :const:`None`. If the generator yields a value, a :exc:"
"`RuntimeError` is raised. If the generator raises any other exception, it "
"is propagated to the caller. If the generator has already exited due to an "
"exception or normal exit, :meth:`close` returns :const:`None` and has no "
"other effect."
msgstr
""
#:
../../reference/expressions.rst:644
msgid
""
"If a generator returns a value upon being closed, the value is returned by :"
"meth:`close`."
msgstr
""
#:
../../reference/expressions.rst:650
msgid
"Examples"
msgstr
"模組"
#:
../../reference/expressions.rst:652
msgid
""
"Here is a simple example that demonstrates the behavior of generators and "
"generator functions::"
msgstr
""
#:
../../reference/expressions.rst:655
msgid
""
">>> def echo(value=None):\n"
"... print(
\"
Execution starts when 'next()' is called for the first time."
"
\"
)\n"
"... try:\n"
"... while True:\n"
"... try:\n"
"... value = (yield value)\n"
"... except Exception as e:\n"
"... value = e\n"
"... finally:\n"
"... print(
\"
Don't forget to clean up when 'close()' is called.
\"
)\n"
"...\n"
">>> generator = echo(1)\n"
">>> print(next(generator))\n"
"Execution starts when 'next()' is called for the first time.\n"
"1\n"
">>> print(next(generator))\n"
"None\n"
">>> print(generator.send(2))\n"
"2\n"
">>> generator.throw(TypeError,
\"
spam
\"
)\n"
"TypeError('spam',)\n"
">>> generator.close()\n"
"Don't forget to clean up when 'close()' is called."
msgstr
""
#:
../../reference/expressions.rst:679
msgid
""
"For examples using ``yield from``, see :ref:`pep-380` in
\"
What's New in "
"Python.
\"
"
msgstr
""
#:
../../reference/expressions.rst:685
msgid
"Asynchronous generator functions"
msgstr
"非同步產生器函式"
#:
../../reference/expressions.rst:687
msgid
""
"The presence of a yield expression in a function or method defined using :"
"keyword:`async def` further defines the function as an :term:`asynchronous "
"generator` function."
msgstr
""
#:
../../reference/expressions.rst:691
msgid
""
"When an asynchronous generator function is called, it returns an "
"asynchronous iterator known as an asynchronous generator object. That object "
"then controls the execution of the generator function. An asynchronous "
"generator object is typically used in an :keyword:`async for` statement in a "
"coroutine function analogously to how a generator object would be used in a :"
"keyword:`for` statement."
msgstr
""
#:
../../reference/expressions.rst:698
msgid
""
"Calling one of the asynchronous generator's methods returns an :term:"
"`awaitable` object, and the execution starts when this object is awaited on. "
"At that time, the execution proceeds to the first yield expression, where it "
"is suspended again, returning the value of :token:`~python-grammar:"
"yield_list` to the awaiting coroutine. As with a generator, suspension means "
"that all local state is retained, including the current bindings of local "
"variables, the instruction pointer, the internal evaluation stack, and the "
"state of any exception handling. When the execution is resumed by awaiting "
"on the next object returned by the asynchronous generator's methods, the "
"function can proceed exactly as if the yield expression were just another "
"external call. The value of the yield expression after resuming depends on "
"the method which resumed the execution. If :meth:`~agen.__anext__` is used "
"then the result is :const:`None`. Otherwise, if :meth:`~agen.asend` is used, "
"then the result will be the value passed in to that method."
msgstr
""
#:
../../reference/expressions.rst:713
msgid
""
"If an asynchronous generator happens to exit early by :keyword:`break`, the "
"caller task being cancelled, or other exceptions, the generator's async "
"cleanup code will run and possibly raise exceptions or access context "
"variables in an unexpected context--perhaps after the lifetime of tasks it "
"depends, or during the event loop shutdown when the async-generator garbage "
"collection hook is called. To prevent this, the caller must explicitly close "
"the async generator by calling :meth:`~agen.aclose` method to finalize the "
"generator and ultimately detach it from the event loop."
msgstr
""
#:
../../reference/expressions.rst:723
msgid
""
"In an asynchronous generator function, yield expressions are allowed "
"anywhere in a :keyword:`try` construct. However, if an asynchronous "
"generator is not resumed before it is finalized (by reaching a zero "
"reference count or by being garbage collected), then a yield expression "
"within a :keyword:`!try` construct could result in a failure to execute "
"pending :keyword:`finally` clauses. In this case, it is the responsibility "
"of the event loop or scheduler running the asynchronous generator to call "
"the asynchronous generator-iterator's :meth:`~agen.aclose` method and run "
"the resulting coroutine object, thus allowing any pending :keyword:`!"
"finally` clauses to execute."
msgstr
""
#:
../../reference/expressions.rst:734
msgid
""
"To take care of finalization upon event loop termination, an event loop "
"should define a *finalizer* function which takes an asynchronous generator-"
"iterator and presumably calls :meth:`~agen.aclose` and executes the "
"coroutine. This *finalizer* may be registered by calling :func:`sys."
"set_asyncgen_hooks`. When first iterated over, an asynchronous generator-"
"iterator will store the registered *finalizer* to be called upon "
"finalization. For a reference example of a *finalizer* method see the "
"implementation of ``asyncio.Loop.shutdown_asyncgens`` in :source:`Lib/"
"asyncio/base_events.py`."
msgstr
""
#:
../../reference/expressions.rst:743
msgid
""
"The expression ``yield from <expr>`` is a syntax error when used in an "
"asynchronous generator function."
msgstr
""
#:
../../reference/expressions.rst:750
msgid
"Asynchronous generator-iterator methods"
msgstr
""
#:
../../reference/expressions.rst:752
msgid
""
"This subsection describes the methods of an asynchronous generator iterator, "
"which are used to control the execution of a generator function."
msgstr
""
#:
../../reference/expressions.rst:761
msgid
""
"Returns an awaitable which when run starts to execute the asynchronous "
"generator or resumes it at the last executed yield expression. When an "
"asynchronous generator function is resumed with an :meth:`~agen.__anext__` "
"method, the current yield expression always evaluates to :const:`None` in "
"the returned awaitable, which when run will continue to the next yield "
"expression. The value of the :token:`~python-grammar:yield_list` of the "
"yield expression is the value of the :exc:`StopIteration` exception raised "
"by the completing coroutine. If the asynchronous generator exits without "
"yielding another value, the awaitable instead raises a :exc:"
"`StopAsyncIteration` exception, signalling that the asynchronous iteration "
"has completed."
msgstr
""
#:
../../reference/expressions.rst:773
msgid
""
"This method is normally called implicitly by a :keyword:`async for` loop."
msgstr
""
#:
../../reference/expressions.rst:779
msgid
""
"Returns an awaitable which when run resumes the execution of the "
"asynchronous generator. As with the :meth:`~generator.send` method for a "
"generator, this
\"
sends
\"
a value into the asynchronous generator function, "
"and the *value* argument becomes the result of the current yield expression. "
"The awaitable returned by the :meth:`asend` method will return the next "
"value yielded by the generator as the value of the raised :exc:"
"`StopIteration`, or raises :exc:`StopAsyncIteration` if the asynchronous "
"generator exits without yielding another value. When :meth:`asend` is "
"called to start the asynchronous generator, it must be called with :const:"
"`None` as the argument, because there is no yield expression that could "
"receive the value."
msgstr
""
#:
../../reference/expressions.rst:796
msgid
""
"Returns an awaitable that raises an exception of type ``type`` at the point "
"where the asynchronous generator was paused, and returns the next value "
"yielded by the generator function as the value of the raised :exc:"
"`StopIteration` exception. If the asynchronous generator exits without "
"yielding another value, a :exc:`StopAsyncIteration` exception is raised by "
"the awaitable. If the generator function does not catch the passed-in "
"exception, or raises a different exception, then when the awaitable is run "
"that exception propagates to the caller of the awaitable."
msgstr
""
#:
../../reference/expressions.rst:817
msgid
""
"Returns an awaitable that when run will throw a :exc:`GeneratorExit` into "
"the asynchronous generator function at the point where it was paused. If the "
"asynchronous generator function then exits gracefully, is already closed, or "
"raises :exc:`GeneratorExit` (by not catching the exception), then the "
"returned awaitable will raise a :exc:`StopIteration` exception. Any further "
"awaitables returned by subsequent calls to the asynchronous generator will "
"raise a :exc:`StopAsyncIteration` exception. If the asynchronous generator "
"yields a value, a :exc:`RuntimeError` is raised by the awaitable. If the "
"asynchronous generator raises any other exception, it is propagated to the "
"caller of the awaitable. If the asynchronous generator has already exited "
"due to an exception or normal exit, then further calls to :meth:`aclose` "
"will return an awaitable that does nothing."
msgstr
""
#:
../../reference/expressions.rst:833
msgid
"Primaries"
msgstr
""
#:
../../reference/expressions.rst:837
msgid
""
"Primaries represent the most tightly bound operations of the language. Their "
"syntax is:"
msgstr
""
#:
../../reference/expressions.rst:847
msgid
"Attribute references"
msgstr
""
#:
../../reference/expressions.rst:853
msgid
"An attribute reference is a primary followed by a period and a name:"
msgstr
""
#:
../../reference/expressions.rst:863
msgid
""
"The primary must evaluate to an object of a type that supports attribute "
"references, which most objects do. This object is then asked to produce the "
"attribute whose name is the identifier. The type and value produced is "
"determined by the object. Multiple evaluations of the same attribute "
"reference may yield different objects."
msgstr
""
#:
../../reference/expressions.rst:869
msgid
""
"This production can be customized by overriding the :meth:`~object."
"__getattribute__` method or the :meth:`~object.__getattr__` method. The :"
"meth:`!__getattribute__` method is called first and either returns a value "
"or raises :exc:`AttributeError` if the attribute is not available."
msgstr
""
#:
../../reference/expressions.rst:875
msgid
""
"If an :exc:`AttributeError` is raised and the object has a :meth:`!"
"__getattr__` method, that method is called as a fallback."
msgstr
""
#:
../../reference/expressions.rst:881
msgid
"Subscriptions"
msgstr
""
#:
../../reference/expressions.rst:896
msgid
""
"The subscription of an instance of a :ref:`container class <sequence-types>` "
"will generally select an element from the container. The subscription of a :"
"term:`generic class <generic type>` will generally return a :ref:"
"`GenericAlias <types-genericalias>` object."
msgstr
""
#:
../../reference/expressions.rst:904
View remainder of file in raw view
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