cpython/Lib/code.py at 3.4 · python/cpython · GitHub

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"""Utilities needed to emulate Python's interactive interpreter.

"""

# Inspired by similar code by Jeff Epler and Fredrik Lundh.

import sys

import traceback

from codeop import CommandCompiler, compile_command

__all__ = ["InteractiveInterpreter", "InteractiveConsole", "interact",

"compile_command"]

class InteractiveInterpreter:

"""Base class for InteractiveConsole.

This class deals with parsing and interpreter state (the user's

namespace); it doesn't deal with input buffering or prompting or

input file naming (the filename is always passed in explicitly).

"""

def __init__(self, locals=None):

"""Constructor.

The optional 'locals' argument specifies the dictionary in

which code will be executed; it defaults to a newly created

dictionary with key "__name__" set to "__console__" and key

"__doc__" set to None.

"""

if locals is None:

locals = {"__name__": "__console__", "__doc__": None}

self.locals = locals

self.compile = CommandCompiler()

def runsource(self, source, filename="<input>", symbol="single"):

"""Compile and run some source in the interpreter.

Arguments are as for compile_command().

One several things can happen:

1) The input is incorrect; compile_command() raised an

exception (SyntaxError or OverflowError). A syntax traceback

will be printed by calling the showsyntaxerror() method.

2) The input is incomplete, and more input is required;

compile_command() returned None. Nothing happens.

3) The input is complete; compile_command() returned a code

object. The code is executed by calling self.runcode() (which

also handles run-time exceptions, except for SystemExit).

The return value is True in case 2, False in the other cases (unless

an exception is raised). The return value can be used to

decide whether to use sys.ps1 or sys.ps2 to prompt the next

line.

"""

try:

code = self.compile(source, filename, symbol)

except (OverflowError, SyntaxError, ValueError):

# Case 1

self.showsyntaxerror(filename)

return False

if code is None:

# Case 2

return True

# Case 3

self.runcode(code)

return False

def runcode(self, code):

"""Execute a code object.

When an exception occurs, self.showtraceback() is called to

display a traceback. All exceptions are caught except

SystemExit, which is reraised.

A note about KeyboardInterrupt: this exception may occur

elsewhere in this code, and may not always be caught. The

caller should be prepared to deal with it.

"""

try:

exec(code, self.locals)

except SystemExit:

raise

except:

self.showtraceback()

def showsyntaxerror(self, filename=None):

"""Display the syntax error that just occurred.

This doesn't display a stack trace because there isn't one.

If a filename is given, it is stuffed in the exception instead

of what was there before (because Python's parser always uses

"<string>" when reading from a string).

The output is written by self.write(), below.

"""

type, value, tb = sys.exc_info()

sys.last_type = type

sys.last_value = value

sys.last_traceback = tb

if filename and type is SyntaxError:

# Work hard to stuff the correct filename in the exception

try:

msg, (dummy_filename, lineno, offset, line) = value.args

except ValueError:

# Not the format we expect; leave it alone

pass

else:

# Stuff in the right filename

value = SyntaxError(msg, (filename, lineno, offset, line))

sys.last_value = value

if sys.excepthook is sys.__excepthook__:

lines = traceback.format_exception_only(type, value)

self.write(''.join(lines))

else:

# If someone has set sys.excepthook, we let that take precedence

# over self.write

sys.excepthook(type, value, tb)

def showtraceback(self):

"""Display the exception that just occurred.

We remove the first stack item because it is our own code.

The output is written by self.write(), below.

"""

try:

type, value, tb = sys.exc_info()

sys.last_type = type

sys.last_value = value

sys.last_traceback = tb

tblist = traceback.extract_tb(tb)

del tblist[:1]

lines = traceback.format_list(tblist)

if lines:

lines.insert(0, "Traceback (most recent call last):\n")

lines.extend(traceback.format_exception_only(type, value))

finally:

tblist = tb = None

if sys.excepthook is sys.__excepthook__:

self.write(''.join(lines))

else:

# If someone has set sys.excepthook, we let that take precedence

# over self.write

sys.excepthook(type, value, tb)

def write(self, data):

"""Write a string.

The base implementation writes to sys.stderr; a subclass may

replace this with a different implementation.

"""

sys.stderr.write(data)

class InteractiveConsole(InteractiveInterpreter):

"""Closely emulate the behavior of the interactive Python interpreter.

This class builds on InteractiveInterpreter and adds prompting

using the familiar sys.ps1 and sys.ps2, and input buffering.

"""

def __init__(self, locals=None, filename="<console>"):

"""Constructor.

The optional locals argument will be passed to the

InteractiveInterpreter base class.

The optional filename argument should specify the (file)name

of the input stream; it will show up in tracebacks.

"""

InteractiveInterpreter.__init__(self, locals)

self.filename = filename

self.resetbuffer()

def resetbuffer(self):

"""Reset the input buffer."""

self.buffer = []

def interact(self, banner=None):

"""Closely emulate the interactive Python console.

The optional banner argument specifies the banner to print

before the first interaction; by default it prints a banner

similar to the one printed by the real Python interpreter,

followed by the current class name in parentheses (so as not

to confuse this with the real interpreter -- since it's so

close!).

"""

try:

sys.ps1

except AttributeError:

sys.ps1 = ">>> "

try:

sys.ps2

except AttributeError:

sys.ps2 = "... "

cprt = 'Type "help", "copyright", "credits" or "license" for more information.'

if banner is None:

self.write("Python %s on %s\n%s\n(%s)\n" %

(sys.version, sys.platform, cprt,

self.__class__.__name__))

elif banner:

self.write("%s\n" % str(banner))

more = 0

while 1:

try:

if more:

prompt = sys.ps2

else:

prompt = sys.ps1

try:

line = self.raw_input(prompt)

except EOFError:

self.write("\n")

break

else:

more = self.push(line)

except KeyboardInterrupt:

self.write("\nKeyboardInterrupt\n")

self.resetbuffer()

more = 0

def push(self, line):

"""Push a line to the interpreter.

The line should not have a trailing newline; it may have

internal newlines. The line is appended to a buffer and the

interpreter's runsource() method is called with the

concatenated contents of the buffer as source. If this

indicates that the command was executed or invalid, the buffer

is reset; otherwise, the command is incomplete, and the buffer

is left as it was after the line was appended. The return

value is 1 if more input is required, 0 if the line was dealt

with in some way (this is the same as runsource()).

"""

self.buffer.append(line)

source = "\n".join(self.buffer)

more = self.runsource(source, self.filename)

if not more:

self.resetbuffer()

return more

def raw_input(self, prompt=""):

"""Write a prompt and read a line.

The returned line does not include the trailing newline.

When the user enters the EOF key sequence, EOFError is raised.

The base implementation uses the built-in function

input(); a subclass may replace this with a different

implementation.

"""

return input(prompt)

def interact(banner=None, readfunc=None, local=None):

"""Closely emulate the interactive Python interpreter.

This is a backwards compatible interface to the InteractiveConsole

class. When readfunc is not specified, it attempts to import the

readline module to enable GNU readline if it is available.

Arguments (all optional, all default to None):

banner -- passed to InteractiveConsole.interact()

readfunc -- if not None, replaces InteractiveConsole.raw_input()

local -- passed to InteractiveInterpreter.__init__()

"""

console = InteractiveConsole(local)

if readfunc is not None:

console.raw_input = readfunc

else:

try:

import readline

except ImportError:

pass

console.interact(banner)

if __name__ == "__main__":

interact()

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