542 lines
20 KiB
Python
542 lines
20 KiB
Python
"""Extract, format and print information about Python stack traces."""
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import sys
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import operator
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import linecache2 as linecache
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from six import u
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__all__ = ['extract_stack', 'extract_tb', 'format_exception',
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'format_exception_only', 'format_list', 'format_stack',
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'format_tb', 'print_exc', 'format_exc', 'print_exception',
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'print_last', 'print_stack', 'print_tb',
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'clear_frames']
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#
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# Formatting and printing lists of traceback lines.
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#
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def print_list(extracted_list, file=None):
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"""Print the list of tuples as returned by extract_tb() or
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extract_stack() as a formatted stack trace to the given file."""
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if file is None:
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file = sys.stderr
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for item in StackSummary.from_list(extracted_list).format():
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file.write(item)
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def format_list(extracted_list):
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"""Format a list of traceback entry tuples for printing.
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Given a list of tuples as returned by extract_tb() or
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extract_stack(), return a list of strings ready for printing.
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Each string in the resulting list corresponds to the item with the
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same index in the argument list. Each string ends in a newline;
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the strings may contain internal newlines as well, for those items
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whose source text line is not None.
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"""
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return StackSummary.from_list(extracted_list).format()
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#
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# Printing and Extracting Tracebacks.
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#
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def print_tb(tb, limit=None, file=None):
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"""Print up to 'limit' stack trace entries from the traceback 'tb'.
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If 'limit' is omitted or None, all entries are printed. If 'file'
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is omitted or None, the output goes to sys.stderr; otherwise
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'file' should be an open file or file-like object with a write()
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method.
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"""
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print_list(extract_tb(tb, limit=limit), file=file)
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def format_tb(tb, limit=None):
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"""A shorthand for 'format_list(extract_tb(tb, limit))'."""
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return extract_tb(tb, limit=limit).format()
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def extract_tb(tb, limit=None):
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"""Return list of up to limit pre-processed entries from traceback.
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This is useful for alternate formatting of stack traces. If
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'limit' is omitted or None, all entries are extracted. A
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pre-processed stack trace entry is a quadruple (filename, line
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number, function name, text) representing the information that is
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usually printed for a stack trace. The text is a string with
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leading and trailing whitespace stripped; if the source is not
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available it is None.
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"""
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return StackSummary.extract(walk_tb(tb), limit=limit)
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#
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# Exception formatting and output.
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#
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_cause_message = (
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"\nThe above exception was the direct cause "
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"of the following exception:\n\n")
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_context_message = (
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"\nDuring handling of the above exception, "
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"another exception occurred:\n\n")
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def print_exception(etype, value, tb, limit=None, file=None, chain=True):
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"""Print exception up to 'limit' stack trace entries from 'tb' to 'file'.
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This differs from print_tb() in the following ways: (1) if
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traceback is not None, it prints a header "Traceback (most recent
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call last):"; (2) it prints the exception type and value after the
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stack trace; (3) if type is SyntaxError and value has the
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appropriate format, it prints the line where the syntax error
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occurred with a caret on the next line indicating the approximate
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position of the error.
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"""
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if file is None:
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file = sys.stderr
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for line in TracebackException(
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etype, value, tb, limit=limit).format(chain=chain):
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file.write(line)
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def format_exception(etype, value, tb, limit=None, chain=True):
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"""Format a stack trace and the exception information.
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The arguments have the same meaning as the corresponding arguments
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to print_exception(). The return value is a list of strings, each
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ending in a newline and some containing internal newlines. When
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these lines are concatenated and printed, exactly the same text is
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printed as does print_exception().
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"""
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return list(TracebackException(
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etype, value, tb, limit=limit).format(chain=chain))
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def format_exception_only(etype, value):
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"""Format the exception part of a traceback.
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The arguments are the exception type and value such as given by
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sys.last_type and sys.last_value. The return value is a list of
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strings, each ending in a newline.
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Normally, the list contains a single string; however, for
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SyntaxError exceptions, it contains several lines that (when
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printed) display detailed information about where the syntax
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error occurred.
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The message indicating which exception occurred is always the last
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string in the list.
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"""
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return list(TracebackException(etype, value, None).format_exception_only())
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# -- not offical API but folk probably use these two functions.
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def _format_final_exc_line(etype, value):
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valuestr = _some_str(value)
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if value == 'None' or value is None or not valuestr:
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line = "%s\n" % etype
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else:
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line = "%s: %s\n" % (etype, valuestr)
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return line
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def _some_str(value):
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try:
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return str(value)
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except:
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return '<unprintable %s object>' % type(value).__name__
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# --
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def print_exc(limit=None, file=None, chain=True):
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"""Shorthand for 'print_exception(*sys.exc_info(), limit, file)'."""
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print_exception(*sys.exc_info(), limit=limit, file=file, chain=chain)
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def format_exc(limit=None, chain=True):
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"""Like print_exc() but return a string."""
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return "".join(format_exception(*sys.exc_info(), limit=limit, chain=chain))
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def print_last(limit=None, file=None, chain=True):
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"""This is a shorthand for 'print_exception(sys.last_type,
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sys.last_value, sys.last_traceback, limit, file)'."""
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if not hasattr(sys, "last_type"):
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raise ValueError("no last exception")
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print_exception(sys.last_type, sys.last_value, sys.last_traceback,
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limit, file, chain)
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#
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# Printing and Extracting Stacks.
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#
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def print_stack(f=None, limit=None, file=None):
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"""Print a stack trace from its invocation point.
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The optional 'f' argument can be used to specify an alternate
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stack frame at which to start. The optional 'limit' and 'file'
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arguments have the same meaning as for print_exception().
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"""
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print_list(extract_stack(f, limit=limit), file=file)
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def format_stack(f=None, limit=None):
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"""Shorthand for 'format_list(extract_stack(f, limit))'."""
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return format_list(extract_stack(f, limit=limit))
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def extract_stack(f=None, limit=None):
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"""Extract the raw traceback from the current stack frame.
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The return value has the same format as for extract_tb(). The
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optional 'f' and 'limit' arguments have the same meaning as for
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print_stack(). Each item in the list is a quadruple (filename,
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line number, function name, text), and the entries are in order
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from oldest to newest stack frame.
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"""
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stack = StackSummary.extract(walk_stack(f), limit=limit)
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stack.reverse()
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return stack
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_identity = lambda:None
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def clear_frames(tb):
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"Clear all references to local variables in the frames of a traceback."
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while tb is not None:
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try:
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getattr(tb.tb_frame, 'clear', _identity)()
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except RuntimeError:
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# Ignore the exception raised if the frame is still executing.
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pass
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tb = tb.tb_next
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class FrameSummary:
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"""A single frame from a traceback.
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- :attr:`filename` The filename for the frame.
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- :attr:`lineno` The line within filename for the frame that was
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active when the frame was captured.
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- :attr:`name` The name of the function or method that was executing
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when the frame was captured.
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- :attr:`line` The text from the linecache module for the
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of code that was running when the frame was captured.
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- :attr:`locals` Either None if locals were not supplied, or a dict
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mapping the name to the str() of the variable.
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"""
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__slots__ = ('filename', 'lineno', 'name', '_line', 'locals')
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def __init__(self, filename, lineno, name, lookup_line=True, locals=None,
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line=None):
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"""Construct a FrameSummary.
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:param lookup_line: If True, `linecache` is consulted for the source
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code line. Otherwise, the line will be looked up when first needed.
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:param locals: If supplied the frame locals, which will be captured as
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strings.
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:param line: If provided, use this instead of looking up the line in
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the linecache.
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"""
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self.filename = filename
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self.lineno = lineno
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self.name = name
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self._line = line
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if lookup_line:
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self.line
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self.locals = \
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dict((k, str(v)) for k, v in locals.items()) if locals else None
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def __eq__(self, other):
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return (self.filename == other.filename and
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self.lineno == other.lineno and
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self.name == other.name and
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self.locals == other.locals)
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def __getitem__(self, pos):
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return (self.filename, self.lineno, self.name, self.line)[pos]
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def __iter__(self):
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return iter([self.filename, self.lineno, self.name, self.line])
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def __repr__(self):
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return "<FrameSummary file {filename}, line {lineno} in {name}>".format(
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filename=self.filename, lineno=self.lineno, name=self.name)
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@property
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def line(self):
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if self._line is None:
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self._line = linecache.getline(self.filename, self.lineno).strip()
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return self._line
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def walk_stack(f):
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"""Walk a stack yielding the frame and line number for each frame.
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This will follow f.f_back from the given frame. If no frame is given, the
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current stack is used. Usually used with StackSummary.extract.
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"""
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if f is None:
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f = sys._getframe().f_back.f_back
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while f is not None:
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yield f, f.f_lineno
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f = f.f_back
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def walk_tb(tb):
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"""Walk a traceback yielding the frame and line number for each frame.
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This will follow tb.tb_next (and thus is in the opposite order to
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walk_stack). Usually used with StackSummary.extract.
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"""
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while tb is not None:
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yield tb.tb_frame, tb.tb_lineno
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tb = tb.tb_next
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class StackSummary(list):
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"""A stack of frames."""
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@classmethod
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def extract(klass, frame_gen, limit=None, lookup_lines=True):
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"""Create a StackSummary from a traceback or stack object.
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:param frame_gen: A generator that yields (frame, lineno) tuples to
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include in the stack.
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:param limit: None to include all frames or the number of frames to
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include.
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:param lookup_lines: If True, lookup lines for each frame immediately,
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otherwise lookup is deferred until the frame is rendered.
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"""
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if limit is None:
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limit = getattr(sys, 'tracebacklimit', None)
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result = klass()
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fnames = set()
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for pos, (f, lineno) in enumerate(frame_gen):
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if limit is not None and pos >= limit:
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break
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co = f.f_code
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filename = co.co_filename
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name = co.co_name
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fnames.add(filename)
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linecache.lazycache(filename, f.f_globals)
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# Must defer line lookups until we have called checkcache.
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result.append(FrameSummary(filename, lineno, name, lookup_line=False))
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for filename in fnames:
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linecache.checkcache(filename)
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# If immediate lookup was desired, trigger lookups now.
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if lookup_lines:
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for f in result:
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f.line
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return result
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@classmethod
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def from_list(klass, a_list):
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"""Create a StackSummary from a simple list of tuples.
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This method supports the older Python API. Each tuple should be a
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4-tuple with (filename, lineno, name, line) elements.
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"""
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if isinstance(a_list, StackSummary):
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return StackSummary(a_list)
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result = StackSummary()
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for filename, lineno, name, line in a_list:
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result.append(FrameSummary(filename, lineno, name, line=line))
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return result
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def format(self):
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"""Format the stack ready for printing.
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Returns a list of strings ready for printing. Each string in the
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resulting list corresponds to a single frame from the stack.
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Each string ends in a newline; the strings may contain internal
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newlines as well, for those items with source text lines.
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"""
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result = []
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for filename, lineno, name, line in self:
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item = u(' File "{0}", line {1}, in {2}\n').format(filename, lineno, name)
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if line:
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item = item + u(' {0}\n').format(line.strip())
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result.append(item)
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return result
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class TracebackException:
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"""An exception ready for rendering.
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The traceback module captures enough attributes from the original exception
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to this intermediary form to ensure that no references are held, while
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still being able to fully print or format it.
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Use `from_exception` to create TracebackException instances from exception
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objects, or the constructor to create TracebackException instances from
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individual components.
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- :attr:`__cause__` A TracebackException of the original *__cause__*.
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- :attr:`__context__` A TracebackException of the original *__context__*.
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- :attr:`__suppress_context__` The *__suppress_context__* value from the
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original exception.
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- :attr:`stack` A `StackSummary` representing the traceback.
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- :attr:`exc_type` The class of the original traceback.
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- :attr:`filename` For syntax errors - the filename where the error
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occured.
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- :attr:`lineno` For syntax errors - the linenumber where the error
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occured.
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- :attr:`text` For syntax errors - the text where the error
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occured.
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- :attr:`offset` For syntax errors - the offset into the text where the
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error occured.
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- :attr:`msg` For syntax errors - the compiler error message.
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"""
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def __init__(self, exc_type, exc_value, exc_traceback, limit=None,
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lookup_lines=True, _seen=None):
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# NB: we need to accept exc_traceback, exc_value, exc_traceback to
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# permit backwards compat with the existing API, otherwise we
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# need stub thunk objects just to glue it together.
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# Handle loops in __cause__ or __context__.
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if _seen is None:
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_seen = set()
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_seen.add(exc_value)
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# Gracefully handle (the way Python 2.4 and earlier did) the case of
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# being called with no type or value (None, None, None).
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if (exc_value and getattr(exc_value, '__cause__', None) is not None
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and exc_value.__cause__ not in _seen):
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cause = TracebackException(
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type(exc_value.__cause__),
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exc_value.__cause__,
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exc_value.__cause__.__traceback__,
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limit=limit,
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lookup_lines=False,
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_seen=_seen)
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else:
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cause = None
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if (exc_value and getattr(exc_value, '__context__', None) is not None
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and exc_value.__context__ not in _seen):
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context = TracebackException(
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type(exc_value.__context__),
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exc_value.__context__,
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exc_value.__context__.__traceback__,
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limit=limit,
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lookup_lines=False,
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_seen=_seen)
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else:
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context = None
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self.__cause__ = cause
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self.__context__ = context
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self.__suppress_context__ = \
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getattr(exc_value, '__suppress_context__', False) if exc_value else False
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# TODO: locals.
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self.stack = StackSummary.extract(
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walk_tb(exc_traceback), limit=limit, lookup_lines=lookup_lines)
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self.exc_type = exc_type
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# Capture now to permit freeing resources: only complication is in the
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# unofficial API _format_final_exc_line
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self._str = _some_str(exc_value)
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if exc_type and issubclass(exc_type, SyntaxError):
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# Handle SyntaxError's specially
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self.filename = exc_value.filename
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self.lineno = str(exc_value.lineno)
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self.text = exc_value.text
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self.offset = exc_value.offset
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self.msg = exc_value.msg
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if lookup_lines:
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self._load_lines()
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@classmethod
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def from_exception(self, exc, *args, **kwargs):
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"""Create a TracebackException from an exception.
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Only useful in Python 3 specific code.
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"""
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return TracebackException(
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type(exc), exc, exc.__traceback__, *args, **kwargs)
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def _load_lines(self):
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"""Private API. force all lines in the stack to be loaded."""
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for frame in self.stack:
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frame.line
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if self.__context__:
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self.__context__._load_lines()
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if self.__cause__:
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self.__cause__._load_lines()
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def __eq__(self, other):
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return self.__dict__ == other.__dict__
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def __str__(self):
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return self._str
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def format_exception_only(self):
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"""Format the exception part of the traceback.
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The return value is a generator of strings, each ending in a newline.
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Normally, the generator emits a single string; however, for
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SyntaxError exceptions, it emites several lines that (when
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printed) display detailed information about where the syntax
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error occurred.
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The message indicating which exception occurred is always the last
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string in the output.
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"""
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if self.exc_type is None:
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yield _format_final_exc_line(None, self._str)
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return
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stype = getattr(self.exc_type, '__qualname__', self.exc_type.__name__)
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smod = u(self.exc_type.__module__)
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if smod not in ("__main__", "builtins"):
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stype = smod + u('.') + stype
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if not issubclass(self.exc_type, SyntaxError):
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yield _format_final_exc_line(stype, self._str)
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return
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# It was a syntax error; show exactly where the problem was found.
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filename = self.filename or u("<string>")
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lineno = str(self.lineno) or u('?')
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yield u(' File "{0}", line {1}\n').format(filename, lineno)
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badline = u(self.text)
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offset = self.offset
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if badline is not None:
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yield u(' {0}\n').format(badline.strip())
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if offset is not None:
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caretspace = badline.rstrip('\n')
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offset = min(len(caretspace), offset) - 1
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caretspace = caretspace[:offset].lstrip()
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# non-space whitespace (likes tabs) must be kept for alignment
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caretspace = ((c.isspace() and c or ' ') for c in caretspace)
|
|
yield u(' {0}^\n').format(''.join(caretspace))
|
|
msg = self.msg or u("<no detail available>")
|
|
yield u("{0}: {1}\n").format(stype, msg)
|
|
|
|
def format(self, chain=True):
|
|
"""Format the exception.
|
|
|
|
If chain is not *True*, *__cause__* and *__context__* will not be formatted.
|
|
|
|
The return value is a generator of strings, each ending in a newline and
|
|
some containing internal newlines. `print_exception` is a wrapper around
|
|
this method which just prints the lines to a file.
|
|
|
|
The message indicating which exception occurred is always the last
|
|
string in the output.
|
|
"""
|
|
if chain:
|
|
if self.__cause__ is not None:
|
|
for line in self.__cause__.format(chain=chain):
|
|
yield line
|
|
yield _cause_message
|
|
elif (self.__context__ is not None and
|
|
not self.__suppress_context__):
|
|
for line in self.__context__.format(chain=chain):
|
|
yield line
|
|
yield _context_message
|
|
yield u('Traceback (most recent call last):\n')
|
|
for line in self.stack.format():
|
|
yield line
|
|
for line in self.format_exception_only():
|
|
yield line
|