traceback

Extract, format and print information about Python stack traces.

Classes

FrameSummary

A single frame from a traceback.

    - :attr:`filename` The filename for the frame.
    - :attr:`lineno` The line within filename for the frame that was
      active when the frame was captured.
    - :attr:`name` The name of the function or method that was executing
      when the frame was captured.
    - :attr:`line` The text from the linecache module for the
      of code that was running when the frame was captured.
    - :attr:`locals` Either None if locals were not supplied, or a dict
      mapping the name to the repr() of the variable.

filename = <member 'filename' of 'FrameSummary' objects>

line = <property object at 0x7f05677fa6d0>

lineno = <member 'lineno' of 'FrameSummary' objects>

locals = <member 'locals' of 'FrameSummary' objects>

name = <member 'name' of 'FrameSummary' objects>

StackSummary

A stack of frames.

append(self, object, /)

  Append object to the end of the list.

clear(self, /)

  Remove all items from list.

copy(self, /)

  Return a shallow copy of the list.

count(self, value, /)

  Return number of occurrences of value.

extend(self, iterable, /)

  Extend list by appending elements from the iterable.

extract(frame_gen, *, limit=None, lookup_lines=True, capture_locals=False)

  Create a StackSummary from a traceback or stack object.

          :param frame_gen: A generator that yields (frame, lineno) tuples to
              include in the stack.
          :param limit: None to include all frames or the number of frames to
              include.
          :param lookup_lines: If True, lookup lines for each frame immediately,
              otherwise lookup is deferred until the frame is rendered.
          :param capture_locals: If True, the local variables from each frame will
              be captured as object representations into the FrameSummary.

format(self)

  Format the stack ready for printing.

          Returns a list of strings ready for printing.  Each string in the
          resulting list corresponds to a single frame from the stack.
          Each string ends in a newline; the strings may contain internal
          newlines as well, for those items with source text lines.

          For long sequences of the same frame and line, the first few
          repetitions are shown, followed by a summary line stating the exact
          number of further repetitions.

from_list(a_list)


          Create a StackSummary object from a supplied list of
          FrameSummary objects or old-style list of tuples.

index(self, value, start=0, stop=9223372036854775807, /)

  Return first index of value.

  Raises ValueError if the value is not present.

insert(self, index, object, /)

  Insert object before index.

pop(self, index=-1, /)

  Remove and return item at index (default last).

  Raises IndexError if list is empty or index is out of range.

remove(self, value, /)

  Remove first occurrence of value.

  Raises ValueError if the value is not present.

reverse(self, /)

  Reverse *IN PLACE*.

sort(self, /, *, key=None, reverse=False)

  Sort the list in ascending order and return None.

  The sort is in-place (i.e. the list itself is modified) and stable (i.e. the
  order of two equal elements is maintained).

  If a key function is given, apply it once to each list item and sort them,
  ascending or descending, according to their function values.

  The reverse flag can be set to sort in descending order.

TracebackException

An exception ready for rendering.

    The traceback module captures enough attributes from the original exception
    to this intermediary form to ensure that no references are held, while
    still being able to fully print or format it.

    Use `from_exception` to create TracebackException instances from exception
    objects, or the constructor to create TracebackException instances from
    individual components.

    - :attr:`__cause__` A TracebackException of the original *__cause__*.
    - :attr:`__context__` A TracebackException of the original *__context__*.
    - :attr:`__suppress_context__` The *__suppress_context__* value from the
      original exception.
    - :attr:`stack` A `StackSummary` representing the traceback.
    - :attr:`exc_type` The class of the original traceback.
    - :attr:`filename` For syntax errors - the filename where the error
      occurred.
    - :attr:`lineno` For syntax errors - the linenumber where the error
      occurred.
    - :attr:`text` For syntax errors - the text where the error
      occurred.
    - :attr:`offset` For syntax errors - the offset into the text where the
      error occurred.
    - :attr:`msg` For syntax errors - the compiler error message.

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.

format_exception_only(self)

  Format the exception part of the traceback.

          The return value is a generator of strings, each ending in a newline.

          Normally, the generator emits a single string; however, for
          SyntaxError exceptions, it emits several lines that (when
          printed) display detailed information about where the syntax
          error occurred.

          The message indicating which exception occurred is always the last
          string in the output.

from_exception(exc, *args, **kwargs)

  Create a TracebackException from an exception.

Functions

clear_frames

clear_frames(tb)

  Clear all references to local variables in the frames of a traceback.

extract_stack

extract_stack(f=None, limit=None)

  Extract the raw traceback from the current stack frame.

      The return value has the same format as for extract_tb().  The
      optional 'f' and 'limit' arguments have the same meaning as for
      print_stack().  Each item in the list is a quadruple (filename,
      line number, function name, text), and the entries are in order
      from oldest to newest stack frame.

extract_tb

extract_tb(tb, limit=None)


      Return a StackSummary object representing a list of
      pre-processed entries from traceback.

      This is useful for alternate formatting of stack traces.  If
      'limit' is omitted or None, all entries are extracted.  A
      pre-processed stack trace entry is a FrameSummary object
      containing attributes filename, lineno, name, and line
      representing the information that is usually printed for a stack
      trace.  The line is a string with leading and trailing
      whitespace stripped; if the source is not available it is None.

format_exc

format_exc(limit=None, chain=True)

  Like print_exc() but return a string.

format_exception

format_exception(etype, value, tb, limit=None, chain=True)

  Format a stack trace and the exception information.

      The arguments have the same meaning as the corresponding arguments
      to print_exception().  The return value is a list of strings, each
      ending in a newline and some containing internal newlines.  When
      these lines are concatenated and printed, exactly the same text is
      printed as does print_exception().

format_exception_only

format_exception_only(etype, value)

  Format the exception part of a traceback.

      The arguments are the exception type and value such as given by
      sys.last_type and sys.last_value. The return value is a list of
      strings, each ending in a newline.

      Normally, the list contains a single string; however, for
      SyntaxError exceptions, it contains several lines that (when
      printed) display detailed information about where the syntax
      error occurred.

      The message indicating which exception occurred is always the last
      string in the list.

format_list

format_list(extracted_list)

  Format a list of tuples or FrameSummary objects for printing.

      Given a list of tuples or FrameSummary objects as returned by
      extract_tb() or extract_stack(), return a list of strings ready
      for printing.

      Each string in the resulting list corresponds to the item with the
      same index in the argument list.  Each string ends in a newline;
      the strings may contain internal newlines as well, for those items
      whose source text line is not None.

format_stack

format_stack(f=None, limit=None)

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

format_tb

format_tb(tb, limit=None)

  A shorthand for 'format_list(extract_tb(tb, limit))'.

print_exc

print_exc(limit=None, file=None, chain=True)

  Shorthand for 'print_exception(*sys.exc_info(), limit, file)'.

print_exception

print_exception(etype, value, tb, limit=None, file=None, chain=True)

  Print exception up to 'limit' stack trace entries from 'tb' to 'file'.

      This differs from print_tb() in the following ways: (1) if
      traceback is not None, it prints a header "Traceback (most recent
      call last):"; (2) it prints the exception type and value after the
      stack trace; (3) if type is SyntaxError and value has the
      appropriate format, it prints the line where the syntax error
      occurred with a caret on the next line indicating the approximate
      position of the error.

print_last

print_last(limit=None, file=None, chain=True)

  This is a shorthand for 'print_exception(sys.last_type,
      sys.last_value, sys.last_traceback, limit, file)'.

print_list

print_list(extracted_list, file=None)

  Print the list of tuples as returned by extract_tb() or
      extract_stack() as a formatted stack trace to the given file.

print_stack

print_stack(f=None, limit=None, file=None)

  Print a stack trace from its invocation point.

      The optional 'f' argument can be used to specify an alternate
      stack frame at which to start. The optional 'limit' and 'file'
      arguments have the same meaning as for print_exception().

print_tb

print_tb(tb, limit=None, file=None)

  Print up to 'limit' stack trace entries from the traceback 'tb'.

      If 'limit' is omitted or None, all entries are printed.  If 'file'
      is omitted or None, the output goes to sys.stderr; otherwise
      'file' should be an open file or file-like object with a write()
      method.

walk_stack

walk_stack(f)

  Walk a stack yielding the frame and line number for each frame.

      This will follow f.f_back from the given frame. If no frame is given, the
      current stack is used. Usually used with StackSummary.extract.

walk_tb

walk_tb(tb)

  Walk a traceback yielding the frame and line number for each frame.

      This will follow tb.tb_next (and thus is in the opposite order to
      walk_stack). Usually used with StackSummary.extract.

Modules