• Python 进阶 之 traceback模块


    Traceback模块官方英文描述:

      1 Help on module traceback:
      2 
      3 NAME
      4     traceback - Extract, format and print information about Python stack traces.
      5 
      6 FILE
      7     /usr/lib64/python2.7/traceback.py
      8 
      9 FUNCTIONS
     10     extract_stack(f=None, limit=None)
     11         Extract the raw traceback from the current stack frame.
     12         
     13         The return value has the same format as for extract_tb().  The
     14         optional 'f' and 'limit' arguments have the same meaning as for
     15         print_stack().  Each item in the list is a quadruple (filename,
     16         line number, function name, text), and the entries are in order
     17         from oldest to newest stack frame.
     18     
     19     extract_tb(tb, limit=None)
     20         Return list of up to limit pre-processed entries from traceback.
     21         
     22         This is useful for alternate formatting of stack traces.  If
     23         'limit' is omitted or None, all entries are extracted.  A
     24         pre-processed stack trace entry is a quadruple (filename, line
     25         number, function name, text) representing the information that is
     26         usually printed for a stack trace.  The text is a string with
     27         leading and trailing whitespace stripped; if the source is not
     28         available it is None.
     29     
     30     format_exc(limit=None)
     31         Like print_exc() but return a string.
     32     
     33     format_exception(etype, value, tb, limit=None)
     34         Format a stack trace and the exception information.
     35         
     36         The arguments have the same meaning as the corresponding arguments
     37         to print_exception().  The return value is a list of strings, each
     38         ending in a newline and some containing internal newlines.  When
     39         these lines are concatenated and printed, exactly the same text is
     40         printed as does print_exception().
     41     
     42     format_exception_only(etype, value)
     43         Format the exception part of a traceback.
     44         
     45         The arguments are the exception type and value such as given by
     46         sys.last_type and sys.last_value. The return value is a list of
     47         strings, each ending in a newline.
     48         
     49         Normally, the list contains a single string; however, for
     50         SyntaxError exceptions, it contains several lines that (when
     51         printed) display detailed information about where the syntax
     52         error occurred.
     53         
     54         The message indicating which exception occurred is always the last
     55         string in the list.
     56     
     57     format_list(extracted_list)
     58         Format a list of traceback entry tuples for printing.
     59         
     60         Given a list of tuples as returned by extract_tb() or
     61         extract_stack(), return a list of strings ready for printing.
     62         Each string in the resulting list corresponds to the item with the
     63         same index in the argument list.  Each string ends in a newline;
     64         the strings may contain internal newlines as well, for those items
     65         whose source text line is not None.
     66     
     67     format_stack(f=None, limit=None)
     68         Shorthand for 'format_list(extract_stack(f, limit))'.
     69     
     70     format_tb(tb, limit=None)
     71         A shorthand for 'format_list(extract_stack(f, limit)).
     72     
     73     print_exc(limit=None, file=None)
     74         Shorthand for 'print_exception(sys.exc_type, sys.exc_value, sys.exc_traceback, limit, file)'.
     75         (In fact, it uses sys.exc_info() to retrieve the same information
     76         in a thread-safe way.)
     77     
     78     print_exception(etype, value, tb, limit=None, file=None)
     79         Print exception up to 'limit' stack trace entries from 'tb' to 'file'.
     80         
     81         This differs from print_tb() in the following ways: (1) if
     82         traceback is not None, it prints a header "Traceback (most recent
     83         call last):"; (2) it prints the exception type and value after the
     84         stack trace; (3) if type is SyntaxError and value has the
     85         appropriate format, it prints the line where the syntax error
     86         occurred with a caret on the next line indicating the approximate
     87         position of the error.
     88     
     89     print_last(limit=None, file=None)
     90         This is a shorthand for 'print_exception(sys.last_type,
     91         sys.last_value, sys.last_traceback, limit, file)'.
     92     
     93     print_stack(f=None, limit=None, file=None)
     94         Print a stack trace from its invocation point.
     95         
     96         The optional 'f' argument can be used to specify an alternate
     97         stack frame at which to start. The optional 'limit' and 'file'
     98         arguments have the same meaning as for print_exception().
     99     
    100     print_tb(tb, limit=None, file=None)
    101         Print up to 'limit' stack trace entries from the traceback 'tb'.
    102         
    103         If 'limit' is omitted or None, all entries are printed.  If 'file'
    104         is omitted or None, the output goes to sys.stderr; otherwise
    105         'file' should be an open file or file-like object with a write()
    106         method.
    107     
    108     tb_lineno(tb)
    109         Calculate correct line number of traceback given in tb.
    110         
    111         Obsolete in 2.3.
    112 
    113 DATA
    114     __all__ = ['extract_stack', 'extract_tb', 'format_exception', 'format_...
    115 
    116 (END)

     traceback.py源码(Python2.7.5):

      1 """Extract, format and print information about Python stack traces."""
      2 
      3 import linecache
      4 import sys
      5 import types
      6 
      7 __all__ = ['extract_stack', 'extract_tb', 'format_exception',
      8            'format_exception_only', 'format_list', 'format_stack',
      9            'format_tb', 'print_exc', 'format_exc', 'print_exception',
     10            'print_last', 'print_stack', 'print_tb', 'tb_lineno']
     11 
     12 def _print(file, str='', terminator='
    '):
     13     file.write(str+terminator)
     14 
     15 
     16 def print_list(extracted_list, file=None):
     17     """Print the list of tuples as returned by extract_tb() or
     18     extract_stack() as a formatted stack trace to the given file."""
     19     if file is None:
     20         file = sys.stderr
     21     for filename, lineno, name, line in extracted_list:
     22         _print(file,
     23                '  File "%s", line %d, in %s' % (filename,lineno,name))
     24         if line:
     25             _print(file, '    %s' % line.strip())
     26 
     27 def format_list(extracted_list):
     28     """Format a list of traceback entry tuples for printing.
     29 
     30     Given a list of tuples as returned by extract_tb() or
     31     extract_stack(), return a list of strings ready for printing.
     32     Each string in the resulting list corresponds to the item with the
     33     same index in the argument list.  Each string ends in a newline;
     34     the strings may contain internal newlines as well, for those items
     35     whose source text line is not None.
     36     """
     37     list = []
     38     for filename, lineno, name, line in extracted_list:
     39         item = '  File "%s", line %d, in %s
    ' % (filename,lineno,name)
     40         if line:
     41             item = item + '    %s
    ' % line.strip()
     42         list.append(item)
     43     return list
     44 
     45 
     46 def print_tb(tb, limit=None, file=None):
     47     """Print up to 'limit' stack trace entries from the traceback 'tb'.
     48 
     49     If 'limit' is omitted or None, all entries are printed.  If 'file'
     50     is omitted or None, the output goes to sys.stderr; otherwise
     51     'file' should be an open file or file-like object with a write()
     52     method.
     53     """
     54     if file is None:
     55         file = sys.stderr
     56     if limit is None:
     57         if hasattr(sys, 'tracebacklimit'):
     58             limit = sys.tracebacklimit
     59     n = 0
     60     while tb is not None and (limit is None or n < limit):
     61         f = tb.tb_frame
     62         lineno = tb.tb_lineno
     63         co = f.f_code
     64         filename = co.co_filename
     65         name = co.co_name
     66         _print(file,
     67                '  File "%s", line %d, in %s' % (filename, lineno, name))
     68         linecache.checkcache(filename)
     69         line = linecache.getline(filename, lineno, f.f_globals)
     70         if line: _print(file, '    ' + line.strip())
     71         tb = tb.tb_next
     72         n = n+1
     73 
     74 def format_tb(tb, limit = None):
     75     """A shorthand for 'format_list(extract_stack(f, limit))."""
     76     return format_list(extract_tb(tb, limit))
     77 
     78 def extract_tb(tb, limit = None):
     79     """Return list of up to limit pre-processed entries from traceback.
     80 
     81     This is useful for alternate formatting of stack traces.  If
     82     'limit' is omitted or None, all entries are extracted.  A
     83     pre-processed stack trace entry is a quadruple (filename, line
     84     number, function name, text) representing the information that is
     85     usually printed for a stack trace.  The text is a string with
     86     leading and trailing whitespace stripped; if the source is not
     87     available it is None.
     88     """
     89     if limit is None:
     90         if hasattr(sys, 'tracebacklimit'):
     91             limit = sys.tracebacklimit
     92     list = []
     93     n = 0
     94     while tb is not None and (limit is None or n < limit):
     95         f = tb.tb_frame
     96         lineno = tb.tb_lineno
     97         co = f.f_code
     98         filename = co.co_filename
     99         name = co.co_name
    100         linecache.checkcache(filename)
    101         line = linecache.getline(filename, lineno, f.f_globals)
    102         if line: line = line.strip()
    103         else: line = None
    104         list.append((filename, lineno, name, line))
    105         tb = tb.tb_next
    106         n = n+1
    107     return list
    108 
    109 
    110 def print_exception(etype, value, tb, limit=None, file=None):
    111     """Print exception up to 'limit' stack trace entries from 'tb' to 'file'.
    112 
    113     This differs from print_tb() in the following ways: (1) if
    114     traceback is not None, it prints a header "Traceback (most recent
    115     call last):"; (2) it prints the exception type and value after the
    116     stack trace; (3) if type is SyntaxError and value has the
    117     appropriate format, it prints the line where the syntax error
    118     occurred with a caret on the next line indicating the approximate
    119     position of the error.
    120     """
    121     if file is None:
    122         file = sys.stderr
    123     if tb:
    124         _print(file, 'Traceback (most recent call last):')
    125         print_tb(tb, limit, file)
    126     lines = format_exception_only(etype, value)
    127     for line in lines:
    128         _print(file, line, '')
    129 
    130 def format_exception(etype, value, tb, limit = None):
    131     """Format a stack trace and the exception information.
    132 
    133     The arguments have the same meaning as the corresponding arguments
    134     to print_exception().  The return value is a list of strings, each
    135     ending in a newline and some containing internal newlines.  When
    136     these lines are concatenated and printed, exactly the same text is
    137     printed as does print_exception().
    138     """
    139     if tb:
    140         list = ['Traceback (most recent call last):
    ']
    141         list = list + format_tb(tb, limit)
    142     else:
    143         list = []
    144     list = list + format_exception_only(etype, value)
    145     return list
    146 
    147 def format_exception_only(etype, value):
    148     """Format the exception part of a traceback.
    149 
    150     The arguments are the exception type and value such as given by
    151     sys.last_type and sys.last_value. The return value is a list of
    152     strings, each ending in a newline.
    153 
    154     Normally, the list contains a single string; however, for
    155     SyntaxError exceptions, it contains several lines that (when
    156     printed) display detailed information about where the syntax
    157     error occurred.
    158 
    159     The message indicating which exception occurred is always the last
    160     string in the list.
    161 
    162     """
    163 
    164     # An instance should not have a meaningful value parameter, but
    165     # sometimes does, particularly for string exceptions, such as
    166     # >>> raise string1, string2  # deprecated
    167     #
    168     # Clear these out first because issubtype(string1, SyntaxError)
    169     # would raise another exception and mask the original problem.
    170     if (isinstance(etype, BaseException) or
    171         isinstance(etype, types.InstanceType) or
    172         etype is None or type(etype) is str):
    173         return [_format_final_exc_line(etype, value)]
    174 
    175     stype = etype.__name__
    176 
    177     if not issubclass(etype, SyntaxError):
    178         return [_format_final_exc_line(stype, value)]
    179 
    180     # It was a syntax error; show exactly where the problem was found.
    181     lines = []
    182     try:
    183         msg, (filename, lineno, offset, badline) = value.args
    184     except Exception:
    185         pass
    186     else:
    187         filename = filename or "<string>"
    188         lines.append('  File "%s", line %d
    ' % (filename, lineno))
    189         if badline is not None:
    190             lines.append('    %s
    ' % badline.strip())
    191             if offset is not None:
    192                 caretspace = badline.rstrip('
    ')[:offset].lstrip()
    193                 # non-space whitespace (likes tabs) must be kept for alignment
    194                 caretspace = ((c.isspace() and c or ' ') for c in caretspace)
    195                 # only three spaces to account for offset1 == pos 0
    196                 lines.append('   %s^
    ' % ''.join(caretspace))
    197         value = msg
    198 
    199     lines.append(_format_final_exc_line(stype, value))
    200     return lines
    201 
    202 def _format_final_exc_line(etype, value):
    203     """Return a list of a single line -- normal case for format_exception_only"""
    204     valuestr = _some_str(value)
    205     if value is None or not valuestr:
    206         line = "%s
    " % etype
    207     else:
    208         line = "%s: %s
    " % (etype, valuestr)
    209     return line
    210 
    211 def _some_str(value):
    212     try:
    213         return str(value)
    214     except Exception:
    215         pass
    216     try:
    217         value = unicode(value)
    218         return value.encode("ascii", "backslashreplace")
    219     except Exception:
    220         pass
    221     return '<unprintable %s object>' % type(value).__name__
    222 
    223 
    224 def print_exc(limit=None, file=None):
    225     """Shorthand for 'print_exception(sys.exc_type, sys.exc_value, sys.exc_traceback, limit, file)'.
    226     (In fact, it uses sys.exc_info() to retrieve the same information
    227     in a thread-safe way.)"""
    228     if file is None:
    229         file = sys.stderr
    230     try:
    231         etype, value, tb = sys.exc_info()
    232         print_exception(etype, value, tb, limit, file)
    233     finally:
    234         etype = value = tb = None
    235 
    236 
    237 def format_exc(limit=None):
    238     """Like print_exc() but return a string."""
    239     try:
    240         etype, value, tb = sys.exc_info()
    241         return ''.join(format_exception(etype, value, tb, limit))
    242     finally:
    243         etype = value = tb = None
    244 
    245 
    246 def print_last(limit=None, file=None):
    247     """This is a shorthand for 'print_exception(sys.last_type,
    248     sys.last_value, sys.last_traceback, limit, file)'."""
    249     if not hasattr(sys, "last_type"):
    250         raise ValueError("no last exception")
    251     if file is None:
    252         file = sys.stderr
    253     print_exception(sys.last_type, sys.last_value, sys.last_traceback,
    254                     limit, file)
    255 
    256 
    257 def print_stack(f=None, limit=None, file=None):
    258     """Print a stack trace from its invocation point.
    259 
    260     The optional 'f' argument can be used to specify an alternate
    261     stack frame at which to start. The optional 'limit' and 'file'
    262     arguments have the same meaning as for print_exception().
    263     """
    264     if f is None:
    265         try:
    266             raise ZeroDivisionError
    267         except ZeroDivisionError:
    268             f = sys.exc_info()[2].tb_frame.f_back
    269     print_list(extract_stack(f, limit), file)
    270 
    271 def format_stack(f=None, limit=None):
    272     """Shorthand for 'format_list(extract_stack(f, limit))'."""
    273     if f is None:
    274         try:
    275             raise ZeroDivisionError
    276         except ZeroDivisionError:
    277             f = sys.exc_info()[2].tb_frame.f_back
    278     return format_list(extract_stack(f, limit))
    279 
    280 def extract_stack(f=None, limit = None):
    281     """Extract the raw traceback from the current stack frame.
    282 
    283     The return value has the same format as for extract_tb().  The
    284     optional 'f' and 'limit' arguments have the same meaning as for
    285     print_stack().  Each item in the list is a quadruple (filename,
    286     line number, function name, text), and the entries are in order
    287     from oldest to newest stack frame.
    288     """
    289     if f is None:
    290         try:
    291             raise ZeroDivisionError
    292         except ZeroDivisionError:
    293             f = sys.exc_info()[2].tb_frame.f_back
    294     if limit is None:
    295         if hasattr(sys, 'tracebacklimit'):
    296             limit = sys.tracebacklimit
    297     list = []
    298     n = 0
    299     while f is not None and (limit is None or n < limit):
    300         lineno = f.f_lineno
    301         co = f.f_code
    302         filename = co.co_filename
    303         name = co.co_name
    304         linecache.checkcache(filename)
    305         line = linecache.getline(filename, lineno, f.f_globals)
    306         if line: line = line.strip()
    307         else: line = None
    308         list.append((filename, lineno, name, line))
    309         f = f.f_back
    310         n = n+1
    311     list.reverse()
    312     return list
    313 
    314 def tb_lineno(tb):
    315     """Calculate correct line number of traceback given in tb.
    316 
    317     Obsolete in 2.3.
    318     """
    319     return tb.tb_lineno
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  • 原文地址:https://www.cnblogs.com/JansXin/p/7457921.html
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