5227f0fdcd
InteractiveInterpreter, which handles parsing and interpreter state but doesn't know deal with buffering or prompting or input file naming. And a derived class, InteractiveConsole, which adds buffering and prompting and supports setting the filename once. Also tweak the algorithm in compile_command() a bit so that input consisting of all blank lines or comments always succeeds immediately, and note the fact that apart from SyntaxError it can also raise OverflowError.
370 lines
12 KiB
Python
370 lines
12 KiB
Python
"""Utilities dealing with code objects.
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Inspired by similar code by Jeff Epler and Fredrik Lundh.
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"""
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import sys
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import string
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import traceback
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def compile_command(source, filename="<input>", symbol="single"):
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r"""Compile a command and determine whether it is incomplete.
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Arguments:
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source -- the source string; may contain \n characters
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filename -- optional filename from which source was read; default "<input>"
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symbol -- optional grammar start symbol; "single" (default) or "eval"
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Return value / exceptions raised:
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- Return a code object if the command is complete and valid
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- Return None if the command is incomplete
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- Raise SyntaxError or OverflowError if the command is a syntax error
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(OverflowError if the error is in a numeric constant)
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Approach:
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First, check if the source consists entirely of blank lines and
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comments; if so, replace it with 'pass', because the built-in
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parser doesn't always do the right thing for these.
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Compile three times: as is, with \n, and with \n\n appended. If
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it compiles as is, it's complete. If it compiles with one \n
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appended, we expect more. If it doesn't compile either way, we
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compare the error we get when compiling with \n or \n\n appended.
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If the errors are the same, the code is broken. But if the errors
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are different, we expect more. Not intuitive; not even guaranteed
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to hold in future releases; but this matches the compiler's
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behavior from Python 1.4 through 1.5.2, at least.
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Caveat:
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It is possible (but not likely) that the parser stops parsing
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with a successful outcome before reaching the end of the source;
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in this case, trailing symbols may be ignored instead of causing an
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error. For example, a backslash followed by two newlines may be
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followed by arbitrary garbage. This will be fixed once the API
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for the parser is better.
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"""
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# Check for source consisting of only blank lines and comments
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for line in string.split(source, "\n"):
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line = string.strip(line)
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if line and line[0] != '#':
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break # Leave it alone
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else:
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source = "pass" # Replace it with a 'pass' statement
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err = err1 = err2 = None
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code = code1 = code2 = None
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try:
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code = compile(source, filename, symbol)
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except SyntaxError, err:
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pass
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try:
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code1 = compile(source + "\n", filename, symbol)
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except SyntaxError, err1:
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pass
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try:
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code2 = compile(source + "\n\n", filename, symbol)
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except SyntaxError, err2:
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pass
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if code:
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return code
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try:
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e1 = err1.__dict__
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except AttributeError:
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e1 = err1
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try:
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e2 = err2.__dict__
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except AttributeError:
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e2 = err2
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if not code1 and e1 == e2:
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raise SyntaxError, err1
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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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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 1 in case 2, 0 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 = compile_command(source, filename, symbol)
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except (OverflowError, SyntaxError):
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# Case 1
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self.showsyntaxerror(filename)
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return 0
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if code is None:
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# Case 2
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return 1
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# Case 3
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self.runcode(code)
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return 0
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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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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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try:
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# Assume SyntaxError is a class exception
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value = SyntaxError(msg, (filename, lineno, offset, line))
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except:
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# If that failed, assume SyntaxError is a string
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value = msg, (filename, lineno, offset, line)
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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 (innermost 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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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, sys.copyright,
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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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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 = string.join(self.buffer, "\n")
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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, locals=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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locals -- passed to InteractiveInterpreter.__init__()
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"""
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console = InteractiveConsole(locals)
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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:
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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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