cpython/Lib/cmd.py at 3.5 · python/cpython · GitHub

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"""A generic class to build line-oriented command interpreters.

Interpreters constructed with this class obey the following conventions:

1. End of file on input is processed as the command 'EOF'.

2. A command is parsed out of each line by collecting the prefix composed

of characters in the identchars member.

3. A command `foo' is dispatched to a method 'do_foo()'; the do_ method

is passed a single argument consisting of the remainder of the line.

4. Typing an empty line repeats the last command. (Actually, it calls the

method `emptyline', which may be overridden in a subclass.)

5. There is a predefined `help' method. Given an argument `topic', it

calls the command `help_topic'. With no arguments, it lists all topics

with defined help_ functions, broken into up to three topics; documented

commands, miscellaneous help topics, and undocumented commands.

6. The command '?' is a synonym for `help'. The command '!' is a synonym

for `shell', if a do_shell method exists.

7. If completion is enabled, completing commands will be done automatically,

and completing of commands args is done by calling complete_foo() with

arguments text, line, begidx, endidx. text is string we are matching

against, all returned matches must begin with it. line is the current

input line (lstripped), begidx and endidx are the beginning and end

indexes of the text being matched, which could be used to provide

different completion depending upon which position the argument is in.

The `default' method may be overridden to intercept commands for which there

is no do_ method.

The `completedefault' method may be overridden to intercept completions for

commands that have no complete_ method.

The data member `self.ruler' sets the character used to draw separator lines

in the help messages. If empty, no ruler line is drawn. It defaults to "=".

If the value of `self.intro' is nonempty when the cmdloop method is called,

it is printed out on interpreter startup. This value may be overridden

via an optional argument to the cmdloop() method.

The data members `self.doc_header', `self.misc_header', and

`self.undoc_header' set the headers used for the help function's

listings of documented functions, miscellaneous topics, and undocumented

functions respectively.

"""

import string, sys

__all__ = ["Cmd"]

PROMPT = '(Cmd) '

IDENTCHARS = string.ascii_letters + string.digits + '_'

class Cmd:

"""A simple framework for writing line-oriented command interpreters.

These are often useful for test harnesses, administrative tools, and

prototypes that will later be wrapped in a more sophisticated interface.

A Cmd instance or subclass instance is a line-oriented interpreter

framework. There is no good reason to instantiate Cmd itself; rather,

it's useful as a superclass of an interpreter class you define yourself

in order to inherit Cmd's methods and encapsulate action methods.

"""

prompt = PROMPT

identchars = IDENTCHARS

ruler = '='

lastcmd = ''

intro = None

doc_leader = ""

doc_header = "Documented commands (type help <topic>):"

misc_header = "Miscellaneous help topics:"

undoc_header = "Undocumented commands:"

nohelp = "*** No help on %s"

use_rawinput = 1

def __init__(self, completekey='tab', stdin=None, stdout=None):

"""Instantiate a line-oriented interpreter framework.

The optional argument 'completekey' is the readline name of a

completion key; it defaults to the Tab key. If completekey is

not None and the readline module is available, command completion

is done automatically. The optional arguments stdin and stdout

specify alternate input and output file objects; if not specified,

sys.stdin and sys.stdout are used.

"""

if stdin is not None:

self.stdin = stdin

else:

self.stdin = sys.stdin

if stdout is not None:

self.stdout = stdout

else:

self.stdout = sys.stdout

self.cmdqueue = []

self.completekey = completekey

def cmdloop(self, intro=None):

"""Repeatedly issue a prompt, accept input, parse an initial prefix

off the received input, and dispatch to action methods, passing them

the remainder of the line as argument.

"""

self.preloop()

if self.use_rawinput and self.completekey:

try:

import readline

self.old_completer = readline.get_completer()

readline.set_completer(self.complete)

readline.parse_and_bind(self.completekey+": complete")

except ImportError:

pass

try:

if intro is not None:

self.intro = intro

if self.intro:

self.stdout.write(str(self.intro)+"\n")

stop = None

while not stop:

if self.cmdqueue:

line = self.cmdqueue.pop(0)

else:

if self.use_rawinput:

try:

line = input(self.prompt)

except EOFError:

line = 'EOF'

else:

self.stdout.write(self.prompt)

self.stdout.flush()

line = self.stdin.readline()

if not len(line):

line = 'EOF'

else:

line = line.rstrip('\r\n')

line = self.precmd(line)

stop = self.onecmd(line)

stop = self.postcmd(stop, line)

self.postloop()

finally:

if self.use_rawinput and self.completekey:

try:

import readline

readline.set_completer(self.old_completer)

except ImportError:

pass

def precmd(self, line):

"""Hook method executed just before the command line is

interpreted, but after the input prompt is generated and issued.

"""

return line

def postcmd(self, stop, line):

"""Hook method executed just after a command dispatch is finished."""

return stop

def preloop(self):

"""Hook method executed once when the cmdloop() method is called."""

pass

def postloop(self):

"""Hook method executed once when the cmdloop() method is about to

return.

"""

pass

def parseline(self, line):

"""Parse the line into a command name and a string containing

the arguments. Returns a tuple containing (command, args, line).

'command' and 'args' may be None if the line couldn't be parsed.

"""

line = line.strip()

if not line:

return None, None, line

elif line[0] == '?':

line = 'help ' + line[1:]

elif line[0] == '!':

if hasattr(self, 'do_shell'):

line = 'shell ' + line[1:]

else:

return None, None, line

i, n = 0, len(line)

while i < n and line[i] in self.identchars: i = i+1

cmd, arg = line[:i], line[i:].strip()

return cmd, arg, line

def onecmd(self, line):

"""Interpret the argument as though it had been typed in response

to the prompt.

This may be overridden, but should not normally need to be;

see the precmd() and postcmd() methods for useful execution hooks.

The return value is a flag indicating whether interpretation of

commands by the interpreter should stop.

"""

cmd, arg, line = self.parseline(line)

if not line:

return self.emptyline()

if cmd is None:

return self.default(line)

self.lastcmd = line

if line == 'EOF' :

self.lastcmd = ''

if cmd == '':

return self.default(line)

else:

try:

func = getattr(self, 'do_' + cmd)

except AttributeError:

return self.default(line)

return func(arg)

def emptyline(self):

"""Called when an empty line is entered in response to the prompt.

If this method is not overridden, it repeats the last nonempty

command entered.

"""

if self.lastcmd:

return self.onecmd(self.lastcmd)

def default(self, line):

"""Called on an input line when the command prefix is not recognized.

If this method is not overridden, it prints an error message and

returns.

"""

self.stdout.write('*** Unknown syntax: %s\n'%line)

def completedefault(self, *ignored):

"""Method called to complete an input line when no command-specific

complete_*() method is available.

By default, it returns an empty list.

"""

return []

def completenames(self, text, *ignored):

dotext = 'do_'+text

return [a[3:] for a in self.get_names() if a.startswith(dotext)]

def complete(self, text, state):

"""Return the next possible completion for 'text'.

If a command has not been entered, then complete against command list.

Otherwise try to call complete_<command> to get list of completions.

"""

if state == 0:

import readline

origline = readline.get_line_buffer()

line = origline.lstrip()

stripped = len(origline) - len(line)

begidx = readline.get_begidx() - stripped

endidx = readline.get_endidx() - stripped

if begidx>0:

cmd, args, foo = self.parseline(line)

if cmd == '':

compfunc = self.completedefault

else:

try:

compfunc = getattr(self, 'complete_' + cmd)

except AttributeError:

compfunc = self.completedefault

else:

compfunc = self.completenames

self.completion_matches = compfunc(text, line, begidx, endidx)

try:

return self.completion_matches[state]

except IndexError:

return None

def get_names(self):

# This method used to pull in base class attributes

# at a time dir() didn't do it yet.

return dir(self.__class__)

def complete_help(self, *args):

commands = set(self.completenames(*args))

topics = set(a[5:] for a in self.get_names()

if a.startswith('help_' + args[0]))

return list(commands | topics)

def do_help(self, arg):

'List available commands with "help" or detailed help with "help cmd".'

if arg:

# XXX check arg syntax

try:

func = getattr(self, 'help_' + arg)

except AttributeError:

try:

doc=getattr(self, 'do_' + arg).__doc__

if doc:

self.stdout.write("%s\n"%str(doc))

return

except AttributeError:

pass

self.stdout.write("%s\n"%str(self.nohelp % (arg,)))

return

func()

else:

names = self.get_names()

cmds_doc = []

cmds_undoc = []

help = {}

for name in names:

if name[:5] == 'help_':

help[name[5:]]=1

names.sort()

# There can be duplicates if routines overridden

prevname = ''

for name in names:

if name[:3] == 'do_':

if name == prevname:

continue

prevname = name

cmd=name[3:]

if cmd in help:

cmds_doc.append(cmd)

del help[cmd]

elif getattr(self, name).__doc__:

cmds_doc.append(cmd)

else:

cmds_undoc.append(cmd)

self.stdout.write("%s\n"%str(self.doc_leader))

self.print_topics(self.doc_header, cmds_doc, 15,80)

self.print_topics(self.misc_header, list(help.keys()),15,80)

self.print_topics(self.undoc_header, cmds_undoc, 15,80)

def print_topics(self, header, cmds, cmdlen, maxcol):

if cmds:

self.stdout.write("%s\n"%str(header))

if self.ruler:

self.stdout.write("%s\n"%str(self.ruler * len(header)))

self.columnize(cmds, maxcol-1)

self.stdout.write("\n")

def columnize(self, list, displaywidth=80):

"""Display a list of strings as a compact set of columns.

Each column is only as wide as necessary.

Columns are separated by two spaces (one was not legible enough).

"""

if not list:

self.stdout.write("<empty>\n")

return

nonstrings = [i for i in range(len(list))

if not isinstance(list[i], str)]

if nonstrings:

raise TypeError("list[i] not a string for i in %s"

% ", ".join(map(str, nonstrings)))

size = len(list)

if size == 1:

self.stdout.write('%s\n'%str(list[0]))

return

# Try every row count from 1 upwards

for nrows in range(1, len(list)):

ncols = (size+nrows-1) // nrows

colwidths = []

totwidth = -2

for col in range(ncols):

colwidth = 0

for row in range(nrows):

i = row + nrows*col

if i >= size:

break

x = list[i]

colwidth = max(colwidth, len(x))

colwidths.append(colwidth)

totwidth += colwidth + 2

if totwidth > displaywidth:

break

if totwidth <= displaywidth:

break

else:

nrows = len(list)

ncols = 1

colwidths = [0]

for row in range(nrows):

texts = []

for col in range(ncols):

i = row + nrows*col

if i >= size:

x = ""

else:

x = list[i]

texts.append(x)

while texts and not texts[-1]:

del texts[-1]

for col in range(len(texts)):

texts[col] = texts[col].ljust(colwidths[col])

self.stdout.write("%s\n"%str(" ".join(texts)))

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