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='\n'):

    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\n' % (filename,lineno,name)

    40         if line:

    41             item = item + '    %s\n' % 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[:-1]:

   128         _print(file, line, ' ')

   129     _print(file, lines[-1], '')

   130 

   131 def format_exception(etype, value, tb, limit = None):

   132     """Format a stack trace and the exception information.

   133 

   134     The arguments have the same meaning as the corresponding arguments

   135     to print_exception().  The return value is a list of strings, each

   136     ending in a newline and some containing internal newlines.  When

   137     these lines are concatenated and printed, exactly the same text is

   138     printed as does print_exception().

   139     """

   140     if tb:

   141         list = ['Traceback (most recent call last):\n']

   142         list = list + format_tb(tb, limit)

   143     else:

   144         list = []

   145     list = list + format_exception_only(etype, value)

   146     return list

   147 

   148 def format_exception_only(etype, value):

   149     """Format the exception part of a traceback.

   150 

   151     The arguments are the exception type and value such as given by

   152     sys.last_type and sys.last_value. The return value is a list of

   153     strings, each ending in a newline.

   154 

   155     Normally, the list contains a single string; however, for

   156     SyntaxError exceptions, it contains several lines that (when

   157     printed) display detailed information about where the syntax

   158     error occurred.

   159 

   160     The message indicating which exception occurred is always the last

   161     string in the list.

   162 

   163     """

   164 

   165     # An instance should not have a meaningful value parameter, but

   166     # sometimes does, particularly for string exceptions, such as

   167     # >>> raise string1, string2  # deprecated

   168     #

   169     # Clear these out first because issubtype(string1, SyntaxError)

   170     # would throw another exception and mask the original problem.

   171     if (isinstance(etype, BaseException) or

   172         isinstance(etype, types.InstanceType) or

   173         etype is None or type(etype) is str):

   174         return [_format_final_exc_line(etype, value)]

   175 

   176     stype = etype.__name__

   177 

   178     if not issubclass(etype, SyntaxError):

   179         return [_format_final_exc_line(stype, value)]

   180 

   181     # It was a syntax error; show exactly where the problem was found.

   182     lines = []

   183     try:

   184         msg, (filename, lineno, offset, badline) = value.args

   185     except Exception:

   186         pass

   187     else:

   188         filename = filename or "<string>"

   189         lines.append('  File "%s", line %d\n' % (filename, lineno))

   190         if badline is not None:

   191             lines.append('    %s\n' % badline.strip())

   192             if offset is not None:

   193                 caretspace = badline[:offset].lstrip()

   194                 # non-space whitespace (likes tabs) must be kept for alignment

   195                 caretspace = ((c.isspace() and c or ' ') for c in caretspace)

   196                 # only three spaces to account for offset1 == pos 0

   197                 lines.append('   %s^\n' % ''.join(caretspace))

   198             value = msg

   199 

   200     lines.append(_format_final_exc_line(stype, value))

   201     return lines

   202 

   203 def _format_final_exc_line(etype, value):

   204     """Return a list of a single line -- normal case for format_exception_only"""

   205     valuestr = _some_str(value)

   206     if value is None or not valuestr:

   207         line = "%s\n" % etype

   208     else:

   209         line = "%s: %s\n" % (etype, valuestr)

   210     return line

   211 

   212 def _some_str(value):

   213     try:

   214         return str(value)

   215     except:

   216         return '<unprintable %s object>' % type(value).__name__

   217 

   218 

   219 def print_exc(limit=None, file=None):

   220     """Shorthand for 'print_exception(sys.exc_type, sys.exc_value, sys.exc_traceback, limit, file)'.

   221     (In fact, it uses sys.exc_info() to retrieve the same information

   222     in a thread-safe way.)"""

   223     if file is None:

   224         file = sys.stderr

   225     try:

   226         etype, value, tb = sys.exc_info()

   227         print_exception(etype, value, tb, limit, file)

   228     finally:

   229         etype = value = tb = None

   230 

   231 

   232 def format_exc(limit=None):

   233     """Like print_exc() but return a string."""

   234     try:

   235         etype, value, tb = sys.exc_info()

   236         return ''.join(format_exception(etype, value, tb, limit))

   237     finally:

   238         etype = value = tb = None

   239 

   240 

   241 def print_last(limit=None, file=None):

   242     """This is a shorthand for 'print_exception(sys.last_type,

   243     sys.last_value, sys.last_traceback, limit, file)'."""

   244     if file is None:

   245         file = sys.stderr

   246     print_exception(sys.last_type, sys.last_value, sys.last_traceback,

   247                     limit, file)

   248 

   249 

   250 def print_stack(f=None, limit=None, file=None):

   251     """Print a stack trace from its invocation point.

   252 

   253     The optional 'f' argument can be used to specify an alternate

   254     stack frame at which to start. The optional 'limit' and 'file'

   255     arguments have the same meaning as for print_exception().

   256     """

   257     if f is None:

   258         try:

   259             raise ZeroDivisionError

   260         except ZeroDivisionError:

   261             f = sys.exc_info()[2].tb_frame.f_back

   262     print_list(extract_stack(f, limit), file)

   263 

   264 def format_stack(f=None, limit=None):

   265     """Shorthand for 'format_list(extract_stack(f, limit))'."""

   266     if f is None:

   267         try:

   268             raise ZeroDivisionError

   269         except ZeroDivisionError:

   270             f = sys.exc_info()[2].tb_frame.f_back

   271     return format_list(extract_stack(f, limit))

   272 

   273 def extract_stack(f=None, limit = None):

   274     """Extract the raw traceback from the current stack frame.

   275 

   276     The return value has the same format as for extract_tb().  The

   277     optional 'f' and 'limit' arguments have the same meaning as for

   278     print_stack().  Each item in the list is a quadruple (filename,

   279     line number, function name, text), and the entries are in order

   280     from oldest to newest stack frame.

   281     """

   282     if f is None:

   283         try:

   284             raise ZeroDivisionError

   285         except ZeroDivisionError:

   286             f = sys.exc_info()[2].tb_frame.f_back

   287     if limit is None:

   288         if hasattr(sys, 'tracebacklimit'):

   289             limit = sys.tracebacklimit

   290     list = []

   291     n = 0

   292     while f is not None and (limit is None or n < limit):

   293         lineno = f.f_lineno

   294         co = f.f_code

   295         filename = co.co_filename

   296         name = co.co_name

   297         linecache.checkcache(filename)

   298         line = linecache.getline(filename, lineno, f.f_globals)

   299         if line: line = line.strip()

   300         else: line = None

   301         list.append((filename, lineno, name, line))

   302         f = f.f_back

   303         n = n+1

   304     list.reverse()

   305     return list

   306 

   307 def tb_lineno(tb):

   308     """Calculate correct line number of traceback given in tb.

   309 

   310     Obsolete in 2.3.

   311     """

   312     return tb.tb_lineno