"""Extract, format and print information about Python stack traces.""" import linecacheimport sysimport types __all__ = ['extract_stack', 'extract_tb', 'format_exception',           'format_exception_only', 'format_list', 'format_stack',           'format_tb', 'print_exc', 'format_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 file is None:        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 file is None:        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.tb_lineno        co = f.f_code        filename = co.co_filename        name = co.co_name        _print(file,               '  File "%s", line %d, in %s' % (filename,lineno,name))        linecache.checkcache(filename)        line = linecache.getline(filename, lineno, f.f_globals)        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.tb_lineno        co = f.f_code        filename = co.co_filename        name = co.co_name        linecache.checkcache(filename)        line = linecache.getline(filename, lineno, f.f_globals)        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 file is None:        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 always the last    string in the list.     """     # An instance should not have a meaningful value parameter, but    # sometimes does, particularly for string exceptions, such as    # >>> raise string1, string2  # deprecated    #    # Clear these out first because issubtype(string1, SyntaxError)    # would throw another exception and mask the original problem.    if (isinstance(etype, BaseException) or        isinstance(etype, types.InstanceType) or        etype is None or type(etype) is str):        return [_format_final_exc_line(etype, value)]     stype = etype.__name__     if not issubclass(etype, SyntaxError):        return [_format_final_exc_line(stype, value)]     # It was a syntax error; show exactly where the problem was found.    lines = []    try:        msg, (filename, lineno, offset, badline) = value    except Exception:        pass    else:        filename = filename or "<string>"        lines.append('  File "%s", line %d\n' % (filename, lineno))        if badline is not None:            lines.append('    %s\n' % badline.strip())            if offset is not None:                caretspace = badline[:offset].lstrip()                # non-space whitespace (likes tabs) must be kept for alignment                caretspace = ((c.isspace() and c or ' ') for c in caretspace)                # only three spaces to account for offset1 == pos 0                lines.append('   %s^\n' % ''.join(caretspace))            value = msg     lines.append(_format_final_exc_line(stype, value))    return lines def _format_final_exc_line(etype, value):    """Return a list of a single line -- normal case for format_exception_only"""    valuestr = _some_str(value)    if value is None or not valuestr:        line = "%s\n" % etype    else:        line = "%s: %s\n" % (etype, valuestr)    return line 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 file is None:        file = sys.stderr    try:        etype, value, tb = sys.exc_info()        print_exception(etype, value, tb, limit, file)    finally:        etype = value = tb = None  def format_exc(limit=None):    """Like print_exc() but return a string."""    try:        etype, value, tb = sys.exc_info()        return ''.join(format_exception(etype, value, tb, limit))    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 file is None:        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        co = f.f_code        filename = co.co_filename        name = co.co_name        linecache.checkcache(filename)        line = linecache.getline(filename, lineno, f.f_globals)        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.     Obsolete in 2.3.    """    return tb.tb_lineno