| """Extract, format and print information about Python stack traces.""" |
| |
| import collections |
| import itertools |
| import linecache |
| import sys |
| |
| __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', 'clear_frames', |
| 'FrameSummary', 'StackSummary', 'TracebackException', |
| 'walk_stack', 'walk_tb'] |
| |
| # |
| # Formatting and printing lists of traceback lines. |
| # |
| |
| 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 item in StackSummary.from_list(extracted_list).format(): |
| print(item, file=file, end="") |
| |
| def 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. |
| """ |
| return StackSummary.from_list(extracted_list).format() |
| |
| # |
| # Printing and Extracting Tracebacks. |
| # |
| |
| 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. |
| """ |
| print_list(extract_tb(tb, limit=limit), file=file) |
| |
| def format_tb(tb, limit=None): |
| """A shorthand for 'format_list(extract_tb(tb, limit))'.""" |
| return extract_tb(tb, limit=limit).format() |
| |
| def 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. |
| """ |
| return StackSummary.extract(walk_tb(tb), limit=limit) |
| |
| # |
| # Exception formatting and output. |
| # |
| |
| _cause_message = ( |
| "\nThe above exception was the direct cause " |
| "of the following exception:\n\n") |
| |
| _context_message = ( |
| "\nDuring handling of the above exception, " |
| "another exception occurred:\n\n") |
| |
| |
| def 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. |
| """ |
| # format_exception has ignored etype for some time, and code such as cgitb |
| # passes in bogus values as a result. For compatibility with such code we |
| # ignore it here (rather than in the new TracebackException API). |
| if file is None: |
| file = sys.stderr |
| for line in TracebackException( |
| type(value), value, tb, limit=limit).format(chain=chain): |
| print(line, file=file, end="") |
| |
| |
| def 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 has ignored etype for some time, and code such as cgitb |
| # passes in bogus values as a result. For compatibility with such code we |
| # ignore it here (rather than in the new TracebackException API). |
| return list(TracebackException( |
| type(value), value, tb, limit=limit).format(chain=chain)) |
| |
| |
| 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. |
| |
| """ |
| return list(TracebackException(etype, value, None).format_exception_only()) |
| |
| |
| # -- not official API but folk probably use these two functions. |
| |
| def _format_final_exc_line(etype, value): |
| 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, chain=True): |
| """Shorthand for 'print_exception(*sys.exc_info(), limit, file)'.""" |
| print_exception(*sys.exc_info(), limit=limit, file=file, chain=chain) |
| |
| def format_exc(limit=None, chain=True): |
| """Like print_exc() but return a string.""" |
| return "".join(format_exception(*sys.exc_info(), limit=limit, chain=chain)) |
| |
| def 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)'.""" |
| if not hasattr(sys, "last_type"): |
| raise ValueError("no last exception") |
| print_exception(sys.last_type, sys.last_value, sys.last_traceback, |
| limit, file, chain) |
| |
| # |
| # Printing and Extracting Stacks. |
| # |
| |
| 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: |
| f = sys._getframe().f_back |
| print_list(extract_stack(f, limit=limit), file=file) |
| |
| |
| def format_stack(f=None, limit=None): |
| """Shorthand for 'format_list(extract_stack(f, limit))'.""" |
| if f is None: |
| f = sys._getframe().f_back |
| return format_list(extract_stack(f, limit=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: |
| f = sys._getframe().f_back |
| stack = StackSummary.extract(walk_stack(f), limit=limit) |
| stack.reverse() |
| return stack |
| |
| |
| def clear_frames(tb): |
| "Clear all references to local variables in the frames of a traceback." |
| while tb is not None: |
| try: |
| tb.tb_frame.clear() |
| except RuntimeError: |
| # Ignore the exception raised if the frame is still executing. |
| pass |
| tb = tb.tb_next |
| |
| |
| class 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. |
| """ |
| |
| __slots__ = ('filename', 'lineno', 'name', '_line', 'locals') |
| |
| def __init__(self, filename, lineno, name, *, lookup_line=True, |
| locals=None, line=None): |
| """Construct a FrameSummary. |
| |
| :param lookup_line: If True, `linecache` is consulted for the source |
| code line. Otherwise, the line will be looked up when first needed. |
| :param locals: If supplied the frame locals, which will be captured as |
| object representations. |
| :param line: If provided, use this instead of looking up the line in |
| the linecache. |
| """ |
| self.filename = filename |
| self.lineno = lineno |
| self.name = name |
| self._line = line |
| if lookup_line: |
| self.line |
| self.locals = {k: repr(v) for k, v in locals.items()} if locals else None |
| |
| def __eq__(self, other): |
| if isinstance(other, FrameSummary): |
| return (self.filename == other.filename and |
| self.lineno == other.lineno and |
| self.name == other.name and |
| self.locals == other.locals) |
| if isinstance(other, tuple): |
| return (self.filename, self.lineno, self.name, self.line) == other |
| return NotImplemented |
| |
| def __getitem__(self, pos): |
| return (self.filename, self.lineno, self.name, self.line)[pos] |
| |
| def __iter__(self): |
| return iter([self.filename, self.lineno, self.name, self.line]) |
| |
| def __repr__(self): |
| return "<FrameSummary file {filename}, line {lineno} in {name}>".format( |
| filename=self.filename, lineno=self.lineno, name=self.name) |
| |
| def __len__(self): |
| return 4 |
| |
| @property |
| def line(self): |
| if self._line is None: |
| self._line = linecache.getline(self.filename, self.lineno).strip() |
| return self._line |
| |
| |
| def 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. |
| """ |
| if f is None: |
| f = sys._getframe().f_back.f_back |
| while f is not None: |
| yield f, f.f_lineno |
| f = f.f_back |
| |
| |
| def 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. |
| """ |
| while tb is not None: |
| yield tb.tb_frame, tb.tb_lineno |
| tb = tb.tb_next |
| |
| |
| _RECURSIVE_CUTOFF = 3 # Also hardcoded in traceback.c. |
| |
| class StackSummary(list): |
| """A stack of frames.""" |
| |
| @classmethod |
| def extract(klass, 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. |
| """ |
| if limit is None: |
| limit = getattr(sys, 'tracebacklimit', None) |
| if limit is not None and limit < 0: |
| limit = 0 |
| if limit is not None: |
| if limit >= 0: |
| frame_gen = itertools.islice(frame_gen, limit) |
| else: |
| frame_gen = collections.deque(frame_gen, maxlen=-limit) |
| |
| result = klass() |
| fnames = set() |
| for f, lineno in frame_gen: |
| co = f.f_code |
| filename = co.co_filename |
| name = co.co_name |
| |
| fnames.add(filename) |
| linecache.lazycache(filename, f.f_globals) |
| # Must defer line lookups until we have called checkcache. |
| if capture_locals: |
| f_locals = f.f_locals |
| else: |
| f_locals = None |
| result.append(FrameSummary( |
| filename, lineno, name, lookup_line=False, locals=f_locals)) |
| for filename in fnames: |
| linecache.checkcache(filename) |
| # If immediate lookup was desired, trigger lookups now. |
| if lookup_lines: |
| for f in result: |
| f.line |
| return result |
| |
| @classmethod |
| def from_list(klass, a_list): |
| """ |
| Create a StackSummary object from a supplied list of |
| FrameSummary objects or old-style list of tuples. |
| """ |
| # While doing a fast-path check for isinstance(a_list, StackSummary) is |
| # appealing, idlelib.run.cleanup_traceback and other similar code may |
| # break this by making arbitrary frames plain tuples, so we need to |
| # check on a frame by frame basis. |
| result = StackSummary() |
| for frame in a_list: |
| if isinstance(frame, FrameSummary): |
| result.append(frame) |
| else: |
| filename, lineno, name, line = frame |
| result.append(FrameSummary(filename, lineno, name, line=line)) |
| return result |
| |
| def 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. |
| """ |
| result = [] |
| last_file = None |
| last_line = None |
| last_name = None |
| count = 0 |
| for frame in self: |
| if (last_file is None or last_file != frame.filename or |
| last_line is None or last_line != frame.lineno or |
| last_name is None or last_name != frame.name): |
| if count > _RECURSIVE_CUTOFF: |
| count -= _RECURSIVE_CUTOFF |
| result.append( |
| f' [Previous line repeated {count} more ' |
| f'time{"s" if count > 1 else ""}]\n' |
| ) |
| last_file = frame.filename |
| last_line = frame.lineno |
| last_name = frame.name |
| count = 0 |
| count += 1 |
| if count > _RECURSIVE_CUTOFF: |
| continue |
| row = [] |
| row.append(' File "{}", line {}, in {}\n'.format( |
| frame.filename, frame.lineno, frame.name)) |
| if frame.line: |
| row.append(' {}\n'.format(frame.line.strip())) |
| if frame.locals: |
| for name, value in sorted(frame.locals.items()): |
| row.append(' {name} = {value}\n'.format(name=name, value=value)) |
| result.append(''.join(row)) |
| if count > _RECURSIVE_CUTOFF: |
| count -= _RECURSIVE_CUTOFF |
| result.append( |
| f' [Previous line repeated {count} more ' |
| f'time{"s" if count > 1 else ""}]\n' |
| ) |
| return result |
| |
| |
| class 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. |
| """ |
| |
| def __init__(self, exc_type, exc_value, exc_traceback, *, limit=None, |
| lookup_lines=True, capture_locals=False, _seen=None): |
| # NB: we need to accept exc_traceback, exc_value, exc_traceback to |
| # permit backwards compat with the existing API, otherwise we |
| # need stub thunk objects just to glue it together. |
| # Handle loops in __cause__ or __context__. |
| if _seen is None: |
| _seen = set() |
| _seen.add(id(exc_value)) |
| # Gracefully handle (the way Python 2.4 and earlier did) the case of |
| # being called with no type or value (None, None, None). |
| if (exc_value and exc_value.__cause__ is not None |
| and id(exc_value.__cause__) not in _seen): |
| cause = TracebackException( |
| type(exc_value.__cause__), |
| exc_value.__cause__, |
| exc_value.__cause__.__traceback__, |
| limit=limit, |
| lookup_lines=False, |
| capture_locals=capture_locals, |
| _seen=_seen) |
| else: |
| cause = None |
| if (exc_value and exc_value.__context__ is not None |
| and id(exc_value.__context__) not in _seen): |
| context = TracebackException( |
| type(exc_value.__context__), |
| exc_value.__context__, |
| exc_value.__context__.__traceback__, |
| limit=limit, |
| lookup_lines=False, |
| capture_locals=capture_locals, |
| _seen=_seen) |
| else: |
| context = None |
| self.__cause__ = cause |
| self.__context__ = context |
| self.__suppress_context__ = \ |
| exc_value.__suppress_context__ if exc_value else False |
| # TODO: locals. |
| self.stack = StackSummary.extract( |
| walk_tb(exc_traceback), limit=limit, lookup_lines=lookup_lines, |
| capture_locals=capture_locals) |
| self.exc_type = exc_type |
| # Capture now to permit freeing resources: only complication is in the |
| # unofficial API _format_final_exc_line |
| self._str = _some_str(exc_value) |
| if exc_type and issubclass(exc_type, SyntaxError): |
| # Handle SyntaxError's specially |
| self.filename = exc_value.filename |
| self.lineno = str(exc_value.lineno) |
| self.text = exc_value.text |
| self.offset = exc_value.offset |
| self.msg = exc_value.msg |
| if lookup_lines: |
| self._load_lines() |
| |
| @classmethod |
| def from_exception(cls, exc, *args, **kwargs): |
| """Create a TracebackException from an exception.""" |
| return cls(type(exc), exc, exc.__traceback__, *args, **kwargs) |
| |
| def _load_lines(self): |
| """Private API. force all lines in the stack to be loaded.""" |
| for frame in self.stack: |
| frame.line |
| if self.__context__: |
| self.__context__._load_lines() |
| if self.__cause__: |
| self.__cause__._load_lines() |
| |
| def __eq__(self, other): |
| if isinstance(other, TracebackException): |
| return self.__dict__ == other.__dict__ |
| return NotImplemented |
| |
| def __str__(self): |
| return self._str |
| |
| def 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. |
| """ |
| if self.exc_type is None: |
| yield _format_final_exc_line(None, self._str) |
| return |
| |
| stype = self.exc_type.__qualname__ |
| smod = self.exc_type.__module__ |
| if smod not in ("__main__", "builtins"): |
| stype = smod + '.' + stype |
| |
| if not issubclass(self.exc_type, SyntaxError): |
| yield _format_final_exc_line(stype, self._str) |
| else: |
| yield from self._format_syntax_error(stype) |
| |
| def _format_syntax_error(self, stype): |
| """Format SyntaxError exceptions (internal helper).""" |
| # Show exactly where the problem was found. |
| filename = self.filename or "<string>" |
| lineno = str(self.lineno) or '?' |
| yield ' File "{}", line {}\n'.format(filename, lineno) |
| |
| text = self.text |
| if text is not None: |
| # text = " foo\n" |
| # rtext = " foo" |
| # ltext = "foo" |
| rtext = text.rstrip('\n') |
| ltext = rtext.lstrip(' \n\f') |
| spaces = len(rtext) - len(ltext) |
| yield ' {}\n'.format(ltext) |
| # Convert 1-based column offset to 0-based index into stripped text |
| caret = (self.offset or 0) - 1 - spaces |
| if caret >= 0: |
| # non-space whitespace (likes tabs) must be kept for alignment |
| caretspace = ((c if c.isspace() else ' ') for c in ltext[:caret]) |
| yield ' {}^\n'.format(''.join(caretspace)) |
| msg = self.msg or "<no detail available>" |
| yield "{}: {}\n".format(stype, msg) |
| |
| def 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. |
| """ |
| if chain: |
| if self.__cause__ is not None: |
| yield from self.__cause__.format(chain=chain) |
| yield _cause_message |
| elif (self.__context__ is not None and |
| not self.__suppress_context__): |
| yield from self.__context__.format(chain=chain) |
| yield _context_message |
| if self.stack: |
| yield 'Traceback (most recent call last):\n' |
| yield from self.stack.format() |
| yield from self.format_exception_only() |
