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svn+ssh://pythondev@svn.python.org/python/branches/py3k ........ r76573 | antoine.pitrou | 2009-11-28 17:12:28 +0100 (sam., 28 nov. 2009) | 3 lines Issue #4486: When an exception has an explicit cause, do not print its implicit context too. ........
341 lines
12 KiB
Python
341 lines
12 KiB
Python
"""Extract, format and print information about Python stack traces."""
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import linecache
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import sys
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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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def _print(file, str='', terminator='\n'):
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file.write(str+terminator)
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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 filename, lineno, name, line in extracted_list:
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_print(file,
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' File "%s", line %d, in %s' % (filename,lineno,name))
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if line:
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_print(file, ' %s' % line.strip())
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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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list = []
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for filename, lineno, name, line in extracted_list:
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item = ' File "%s", line %d, in %s\n' % (filename,lineno,name)
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if line:
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item = item + ' %s\n' % line.strip()
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list.append(item)
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return list
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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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if file is None:
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file = sys.stderr
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if limit is None:
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if hasattr(sys, 'tracebacklimit'):
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limit = sys.tracebacklimit
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n = 0
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while tb is not None and (limit is None or n < limit):
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f = tb.tb_frame
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lineno = tb.tb_lineno
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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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_print(file,
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' File "%s", line %d, in %s' % (filename, lineno, name))
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linecache.checkcache(filename)
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line = linecache.getline(filename, lineno, f.f_globals)
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if line: _print(file, ' ' + line.strip())
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tb = tb.tb_next
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n = n+1
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def format_tb(tb, limit=None):
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"""A shorthand for 'format_list(extract_stack(f, limit))."""
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return format_list(extract_tb(tb, limit))
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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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if limit is None:
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if hasattr(sys, 'tracebacklimit'):
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limit = sys.tracebacklimit
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list = []
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n = 0
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while tb is not None and (limit is None or n < limit):
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f = tb.tb_frame
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lineno = tb.tb_lineno
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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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linecache.checkcache(filename)
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line = linecache.getline(filename, lineno, f.f_globals)
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if line: line = line.strip()
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else: line = None
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list.append((filename, lineno, name, line))
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tb = tb.tb_next
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n = n+1
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return list
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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")
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_context_message = (
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"\nDuring handling of the above exception, "
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"another exception occurred:\n")
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def _iter_chain(exc, custom_tb=None, seen=None):
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if seen is None:
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seen = set()
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seen.add(exc)
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its = []
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cause = exc.__cause__
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if cause is not None and cause not in seen:
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its.append(_iter_chain(cause, None, seen))
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its.append([(_cause_message, None)])
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else:
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context = exc.__context__
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if context is not None and context not in seen:
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its.append(_iter_chain(context, None, seen))
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its.append([(_context_message, None)])
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its.append([(exc, custom_tb or exc.__traceback__)])
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# itertools.chain is in an extension module and may be unavailable
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for it in its:
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for x in it:
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yield x
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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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if chain:
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values = _iter_chain(value, tb)
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else:
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values = [(value, tb)]
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for value, tb in values:
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if isinstance(value, str):
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_print(file, value)
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continue
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if tb:
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_print(file, 'Traceback (most recent call last):')
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print_tb(tb, limit, file)
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lines = format_exception_only(type(value), value)
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for line in lines:
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_print(file, 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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list = []
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if chain:
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values = _iter_chain(value, tb)
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else:
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values = [(value, tb)]
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for value, tb in values:
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if isinstance(value, str):
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list.append(value + '\n')
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continue
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if tb:
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list.append('Traceback (most recent call last):\n')
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list.extend(format_tb(tb, limit))
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list.extend(format_exception_only(type(value), value))
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return list
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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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# Gracefully handle (the way Python 2.4 and earlier did) the case of
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# being called with (None, None).
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if etype is None:
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return [_format_final_exc_line(etype, value)]
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stype = etype.__name__
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smod = etype.__module__
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if smod not in ("__main__", "builtins"):
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stype = smod + '.' + stype
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if not issubclass(etype, SyntaxError):
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return [_format_final_exc_line(stype, value)]
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# It was a syntax error; show exactly where the problem was found.
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lines = []
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filename = value.filename or "<string>"
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lineno = str(value.lineno) or '?'
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lines.append(' File "%s", line %s\n' % (filename, lineno))
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badline = value.text
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offset = value.offset
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if badline is not None:
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lines.append(' %s\n' % badline.strip())
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if offset is not None:
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caretspace = badline.rstrip('\n')[: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)
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# only three spaces to account for offset1 == pos 0
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lines.append(' %s^\n' % ''.join(caretspace))
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msg = value.msg or "<no detail available>"
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lines.append("%s: %s\n" % (stype, msg))
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return lines
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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 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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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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if file is None:
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file = sys.stderr
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try:
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etype, value, tb = sys.exc_info()
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print_exception(etype, value, tb, limit, file, chain)
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finally:
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etype = value = tb = None
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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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try:
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etype, value, tb = sys.exc_info()
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return ''.join(
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format_exception(etype, value, tb, limit, chain))
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finally:
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etype = value = tb = None
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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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if file is None:
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file = sys.stderr
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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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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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if f is None:
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try:
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raise ZeroDivisionError
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except ZeroDivisionError:
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f = sys.exc_info()[2].tb_frame.f_back
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print_list(extract_stack(f, limit), 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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if f is None:
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try:
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raise ZeroDivisionError
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except ZeroDivisionError:
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f = sys.exc_info()[2].tb_frame.f_back
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return format_list(extract_stack(f, 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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if f is None:
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try:
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raise ZeroDivisionError
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except ZeroDivisionError:
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f = sys.exc_info()[2].tb_frame.f_back
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if limit is None:
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if hasattr(sys, 'tracebacklimit'):
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limit = sys.tracebacklimit
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list = []
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n = 0
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while f is not None and (limit is None or n < limit):
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lineno = f.f_lineno
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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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linecache.checkcache(filename)
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line = linecache.getline(filename, lineno, f.f_globals)
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if line: line = line.strip()
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else: line = None
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list.append((filename, lineno, name, line))
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f = f.f_back
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n = n+1
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list.reverse()
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return list
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