Method format

Lib/traceback.py:1537–1635

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 jus

(self, *, chain=True, _ctx=None, **kwargs)

        )

    def format(self, *, chain=True, _ctx=None, **kwargs):
        """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.
        """
        colorize = kwargs.get("colorize", False)
        if _ctx is None:
            _ctx = _ExceptionPrintContext()

        output = []
        exc = self
        if chain:
            while exc:
                if exc.__cause__ is not None:
                    chained_msg = _cause_message
                    chained_exc = exc.__cause__
                elif (exc.__context__  is not None and
                      not exc.__suppress_context__):
                    chained_msg = _context_message
                    chained_exc = exc.__context__
                else:
                    chained_msg = None
                    chained_exc = None

                output.append((chained_msg, exc))
                exc = chained_exc
        else:
            output.append((None, exc))

        for msg, exc in reversed(output):
            if msg is not None:
                yield from _ctx.emit(msg)
            if exc.exceptions is None:
                if exc.stack:
                    yield from _ctx.emit('Traceback (most recent call last):\n')
                    yield from _ctx.emit(exc.stack.format(colorize=colorize))
                yield from _ctx.emit(exc.format_exception_only(colorize=colorize))
            elif _ctx.exception_group_depth > self.max_group_depth:
                # exception group, but depth exceeds limit
                yield from _ctx.emit(
                    f"... (max_group_depth is {self.max_group_depth})\n")
            else:
                # format exception group
                is_toplevel = (_ctx.exception_group_depth == 0)
                if is_toplevel:
                    _ctx.exception_group_depth += 1

                if exc.stack:
                    yield from _ctx.emit(
                        'Exception Group Traceback (most recent call last):\n',
                        margin_char = '+' if is_toplevel else None)