310 lines
10 KiB
Python
310 lines
10 KiB
Python
"""Utilities needed to emulate Python's interactive interpreter.
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"""
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# Inspired by similar code by Jeff Epler and Fredrik Lundh.
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import sys
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import traceback
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from codeop import CommandCompiler, compile_command
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__all__ = ["InteractiveInterpreter", "InteractiveConsole", "interact",
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"compile_command"]
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def softspace(file, newvalue):
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oldvalue = 0
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try:
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oldvalue = file.softspace
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except AttributeError:
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pass
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try:
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file.softspace = newvalue
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except (AttributeError, TypeError):
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# "attribute-less object" or "read-only attributes"
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pass
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return oldvalue
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class InteractiveInterpreter:
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"""Base class for InteractiveConsole.
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This class deals with parsing and interpreter state (the user's
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namespace); it doesn't deal with input buffering or prompting or
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input file naming (the filename is always passed in explicitly).
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"""
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def __init__(self, locals=None):
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"""Constructor.
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The optional 'locals' argument specifies the dictionary in
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which code will be executed; it defaults to a newly created
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dictionary with key "__name__" set to "__console__" and key
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"__doc__" set to None.
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"""
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if locals is None:
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locals = {"__name__": "__console__", "__doc__": None}
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self.locals = locals
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self.compile = CommandCompiler()
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def runsource(self, source, filename="<input>", symbol="single"):
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"""Compile and run some source in the interpreter.
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Arguments are as for compile_command().
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One several things can happen:
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1) The input is incorrect; compile_command() raised an
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exception (SyntaxError or OverflowError). A syntax traceback
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will be printed by calling the showsyntaxerror() method.
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2) The input is incomplete, and more input is required;
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compile_command() returned None. Nothing happens.
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3) The input is complete; compile_command() returned a code
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object. The code is executed by calling self.runcode() (which
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also handles run-time exceptions, except for SystemExit).
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The return value is True in case 2, False in the other cases (unless
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an exception is raised). The return value can be used to
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decide whether to use sys.ps1 or sys.ps2 to prompt the next
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line.
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"""
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try:
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code = self.compile(source, filename, symbol)
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except (OverflowError, SyntaxError, ValueError):
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# Case 1
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self.showsyntaxerror(filename)
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return False
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if code is None:
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# Case 2
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return True
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# Case 3
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self.runcode(code)
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return False
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def runcode(self, code):
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"""Execute a code object.
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When an exception occurs, self.showtraceback() is called to
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display a traceback. All exceptions are caught except
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SystemExit, which is reraised.
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A note about KeyboardInterrupt: this exception may occur
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elsewhere in this code, and may not always be caught. The
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caller should be prepared to deal with it.
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"""
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try:
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exec code in self.locals
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except SystemExit:
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raise
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except:
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self.showtraceback()
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else:
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if softspace(sys.stdout, 0):
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print
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def showsyntaxerror(self, filename=None):
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"""Display the syntax error that just occurred.
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This doesn't display a stack trace because there isn't one.
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If a filename is given, it is stuffed in the exception instead
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of what was there before (because Python's parser always uses
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"<string>" when reading from a string).
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The output is written by self.write(), below.
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"""
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type, value, sys.last_traceback = sys.exc_info()
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sys.last_type = type
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sys.last_value = value
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if filename and type is SyntaxError:
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# Work hard to stuff the correct filename in the exception
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try:
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msg, (dummy_filename, lineno, offset, line) = value
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except:
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# Not the format we expect; leave it alone
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pass
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else:
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# Stuff in the right filename
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value = SyntaxError(msg, (filename, lineno, offset, line))
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sys.last_value = value
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list = traceback.format_exception_only(type, value)
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map(self.write, list)
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def showtraceback(self):
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"""Display the exception that just occurred.
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We remove the first stack item because it is our own code.
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The output is written by self.write(), below.
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"""
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try:
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type, value, tb = sys.exc_info()
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sys.last_type = type
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sys.last_value = value
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sys.last_traceback = tb
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tblist = traceback.extract_tb(tb)
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del tblist[:1]
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list = traceback.format_list(tblist)
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if list:
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list.insert(0, "Traceback (most recent call last):\n")
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list[len(list):] = traceback.format_exception_only(type, value)
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finally:
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tblist = tb = None
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map(self.write, list)
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def write(self, data):
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"""Write a string.
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The base implementation writes to sys.stderr; a subclass may
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replace this with a different implementation.
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"""
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sys.stderr.write(data)
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class InteractiveConsole(InteractiveInterpreter):
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"""Closely emulate the behavior of the interactive Python interpreter.
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This class builds on InteractiveInterpreter and adds prompting
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using the familiar sys.ps1 and sys.ps2, and input buffering.
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"""
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def __init__(self, locals=None, filename="<console>"):
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"""Constructor.
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The optional locals argument will be passed to the
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InteractiveInterpreter base class.
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The optional filename argument should specify the (file)name
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of the input stream; it will show up in tracebacks.
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"""
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InteractiveInterpreter.__init__(self, locals)
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self.filename = filename
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self.resetbuffer()
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def resetbuffer(self):
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"""Reset the input buffer."""
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self.buffer = []
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def interact(self, banner=None):
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"""Closely emulate the interactive Python console.
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The optional banner argument specify the banner to print
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before the first interaction; by default it prints a banner
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similar to the one printed by the real Python interpreter,
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followed by the current class name in parentheses (so as not
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to confuse this with the real interpreter -- since it's so
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close!).
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"""
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try:
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sys.ps1
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except AttributeError:
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sys.ps1 = ">>> "
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try:
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sys.ps2
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except AttributeError:
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sys.ps2 = "... "
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cprt = 'Type "help", "copyright", "credits" or "license" for more information.'
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if banner is None:
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self.write("Python %s on %s\n%s\n(%s)\n" %
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(sys.version, sys.platform, cprt,
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self.__class__.__name__))
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else:
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self.write("%s\n" % str(banner))
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more = 0
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while 1:
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try:
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if more:
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prompt = sys.ps2
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else:
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prompt = sys.ps1
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try:
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line = self.raw_input(prompt)
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# Can be None if sys.stdin was redefined
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encoding = getattr(sys.stdin, "encoding", None)
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if encoding and not isinstance(line, unicode):
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line = line.decode(encoding)
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except EOFError:
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self.write("\n")
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break
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else:
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more = self.push(line)
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except KeyboardInterrupt:
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self.write("\nKeyboardInterrupt\n")
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self.resetbuffer()
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more = 0
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def push(self, line):
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"""Push a line to the interpreter.
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The line should not have a trailing newline; it may have
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internal newlines. The line is appended to a buffer and the
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interpreter's runsource() method is called with the
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concatenated contents of the buffer as source. If this
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indicates that the command was executed or invalid, the buffer
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is reset; otherwise, the command is incomplete, and the buffer
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is left as it was after the line was appended. The return
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value is 1 if more input is required, 0 if the line was dealt
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with in some way (this is the same as runsource()).
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"""
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self.buffer.append(line)
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source = "\n".join(self.buffer)
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more = self.runsource(source, self.filename)
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if not more:
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self.resetbuffer()
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return more
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def raw_input(self, prompt=""):
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"""Write a prompt and read a line.
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The returned line does not include the trailing newline.
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When the user enters the EOF key sequence, EOFError is raised.
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The base implementation uses the built-in function
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raw_input(); a subclass may replace this with a different
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implementation.
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"""
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return raw_input(prompt)
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def interact(banner=None, readfunc=None, local=None):
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"""Closely emulate the interactive Python interpreter.
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This is a backwards compatible interface to the InteractiveConsole
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class. When readfunc is not specified, it attempts to import the
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readline module to enable GNU readline if it is available.
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Arguments (all optional, all default to None):
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banner -- passed to InteractiveConsole.interact()
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readfunc -- if not None, replaces InteractiveConsole.raw_input()
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local -- passed to InteractiveInterpreter.__init__()
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"""
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console = InteractiveConsole(local)
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if readfunc is not None:
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console.raw_input = readfunc
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else:
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try:
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import readline
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except ImportError:
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pass
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console.interact(banner)
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if __name__ == "__main__":
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interact()
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