text: """Extract, format and print information about Python stack traces."""
  
  import linecache
  import sys
  import types
  
  __all__ = ['extract_stack', 'extract_tb', 'format_exception',
             'format_exception_only', 'format_list', 'format_stack',
             'format_tb', 'print_exc', 'print_exception', 'print_last',
             'print_stack', 'print_tb', 'tb_lineno']
  
  def _print(file, str='', terminator='\n'):
      file.write(str+terminator)
  
  
  def 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."""
      if not file:
          file = sys.stderr
      for filename, lineno, name, line in extracted_list:
          _print(file,
                 '  File "%s", line %d, in %s' % (filename,lineno,name))
          if line:
              _print(file, '    %s' % line.strip())
  
  def format_list(extracted_list):
      """Format a list of traceback entry tuples for printing.
  
      Given a list of tuples 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.
      """
      list = []
      for filename, lineno, name, line in extracted_list:
          item = '  File "%s", line %d, in %s\n' % (filename,lineno,name)
          if line:
              item = item + '    %s\n' % line.strip()
          list.append(item)
      return list
  
  
  def 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.
      """
      if not file:
          file = sys.stderr
      if limit is None:
          if hasattr(sys, 'tracebacklimit'):
              limit = sys.tracebacklimit
      n = 0
      while tb is not None and (limit is None or n < limit):
          f = tb.tb_frame
          lineno = tb_lineno(tb)
          co = f.f_code
          filename = co.co_filename
          name = co.co_name
          _print(file,
                 '  File "%s", line %d, in %s' % (filename,lineno,name))
          line = linecache.getline(filename, lineno)
          if line: _print(file, '    ' + line.strip())
          tb = tb.tb_next
          n = n+1
  
  def format_tb(tb, limit = None):
      """A shorthand for 'format_list(extract_stack(f, limit))."""
      return format_list(extract_tb(tb, limit))
  
  def extract_tb(tb, limit = None):
      """Return list of up to limit 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 quadruple (filename, line
      number, function name, text) representing the information that is
      usually printed for a stack trace.  The text is a string with
      leading and trailing whitespace stripped; if the source is not
      available it is None.
      """
      if limit is None:
          if hasattr(sys, 'tracebacklimit'):
              limit = sys.tracebacklimit
      list = []
      n = 0
      while tb is not None and (limit is None or n < limit):
          f = tb.tb_frame
          lineno = tb_lineno(tb)
          co = f.f_code
          filename = co.co_filename
          name = co.co_name
          line = linecache.getline(filename, lineno)
          if line: line = line.strip()
          else: line = None
          list.append((filename, lineno, name, line))
          tb = tb.tb_next
          n = n+1
      return list
  
  
  def print_exception(etype, value, tb, limit=None, file=None):
      """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.
      """
      if not file:
          file = sys.stderr
      if tb:
          _print(file, 'Traceback (most recent call last):')
          print_tb(tb, limit, file)
      lines = format_exception_only(etype, value)
      for line in lines[:-1]:
          _print(file, line, ' ')
      _print(file, lines[-1], '')
  
  def format_exception(etype, value, tb, limit = None):
      """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().
      """
      if tb:
          list = ['Traceback (most recent call last):\n']
          list = list + format_tb(tb, limit)
      else:
          list = []
      list = list + format_exception_only(etype, value)
      return list
  
  def 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 the always last string in the list.
      """
      list = []
      if type(etype) == types.ClassType:
          stype = etype.__name__
      else:
          stype = etype
      if value is None:
          list.append(str(stype) + '\n')
      else:
          if etype is SyntaxError:
              try:
                  msg, (filename, lineno, offset, line) = value
              except:
                  pass
              else:
                  if not filename: filename = "<string>"
                  list.append('  File "%s", line %d\n' %
                              (filename, lineno))
                  if line is not None:
                      i = 0
                      while i < len(line) and line[i].isspace():
                          i = i+1
                      list.append('    %s\n' % line.strip())
                      if offset is not None:
                          s = '    '
                          for c in line[i:offset-1]:
                              if c.isspace():
                                  s = s + c
                              else:
                                  s = s + ' '
                          list.append('%s^\n' % s)
                      value = msg
          s = _some_str(value)
          if s:
              list.append('%s: %s\n' % (str(stype), s))
          else:
              list.append('%s\n' % str(stype))
      return list
  
  def _some_str(value):
      try:
          return str(value)
      except:
          return '<unprintable %s object>' % type(value).__name__
  
  
  def print_exc(limit=None, file=None):
      """Shorthand for 'print_exception(sys.exc_type, sys.exc_value, sys.exc_traceback, limit, file)'.
      (In fact, it uses sys.exc_info() to retrieve the same information
      in a thread-safe way.)"""
      if not file:
          file = sys.stderr
      try:
          etype, value, tb = sys.exc_info()
          print_exception(etype, value, tb, limit, file)
      finally:
          etype = value = tb = None
  
  def print_last(limit=None, file=None):
      """This is a shorthand for 'print_exception(sys.last_type,
      sys.last_value, sys.last_traceback, limit, file)'."""
      if not file:
          file = sys.stderr
      print_exception(sys.last_type, sys.last_value, sys.last_traceback,
                      limit, file)
  
  
  def 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().
      """
      if f is None:
          try:
              raise ZeroDivisionError
          except ZeroDivisionError:
              f = sys.exc_info()[2].tb_frame.f_back
      print_list(extract_stack(f, limit), file)
  
  def format_stack(f=None, limit=None):
      """Shorthand for 'format_list(extract_stack(f, limit))'."""
      if f is None:
          try:
              raise ZeroDivisionError
          except ZeroDivisionError:
              f = sys.exc_info()[2].tb_frame.f_back
      return format_list(extract_stack(f, limit))
  
  def 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.
      """
      if f is None:
          try:
              raise ZeroDivisionError
          except ZeroDivisionError:
              f = sys.exc_info()[2].tb_frame.f_back
      if limit is None:
          if hasattr(sys, 'tracebacklimit'):
              limit = sys.tracebacklimit
      list = []
      n = 0
      while f is not None and (limit is None or n < limit):
          lineno = f.f_lineno     # XXX Too bad if -O is used
          co = f.f_code
          filename = co.co_filename
          name = co.co_name
          line = linecache.getline(filename, lineno)
          if line: line = line.strip()
          else: line = None
          list.append((filename, lineno, name, line))
          f = f.f_back
          n = n+1
      list.reverse()
      return list
  
  def tb_lineno(tb):
      """Calculate correct line number of traceback given in tb.
  
      Even works with -O on.
      """
      # Coded by Marc-Andre Lemburg from the example of PyCode_Addr2Line()
      # in compile.c.
      # Revised version by Jim Hugunin to work with JPython too.
  
      c = tb.tb_frame.f_code
      if not hasattr(c, 'co_lnotab'):
          return tb.tb_lineno
  
      tab = c.co_lnotab
      line = c.co_firstlineno
      stopat = tb.tb_lasti
      addr = 0
      for i in range(0, len(tab), 2):
          addr = addr + ord(tab[i])
          if addr > stopat:
              break
          line = line + ord(tab[i+1])
      return line
  