Class StackSummary

Lib/traceback.py:450–807

A list of FrameSummary objects, representing a stack of frames.

class StackSummary(list):
    """A list of FrameSummary objects, representing 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
            whose summaries are to be included 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.
        """
        def extended_frame_gen():
            for f, lineno in frame_gen:
                yield f, (lineno, None, None, None)

        return klass._extract_from_extended_frame_gen(
            extended_frame_gen(), limit=limit, lookup_lines=lookup_lines,
            capture_locals=capture_locals)

    @classmethod
    def _extract_from_extended_frame_gen(klass, frame_gen, *, limit=None,
            lookup_lines=True, capture_locals=False):
        # Same as extract but operates on a frame generator that yields
        # (frame, (lineno, end_lineno, colno, end_colno)) in the stack.
        # Only lineno is required, the remaining fields can be None if the
        # information is not available.
        builtin_limit = limit is BUILTIN_EXCEPTION_LIMIT
        if limit is None or builtin_limit:
            limit = getattr(sys, 'tracebacklimit', None)
            if limit is not None and limit < 0:
                limit = 0
        if limit is not None:
            if builtin_limit:
                frame_gen = tuple(frame_gen)
                frame_gen = frame_gen[len(frame_gen) - limit:]
            elif 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, end_lineno, colno, end_colno) 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: