"""Extract, format and print information about Python stack traces."""
import collections.abc
import itertools
import linecache
import sys
import textwrap
from contextlib import suppress
__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_from_extended_frame_gen(
_walk_tb_with_full_positions(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")
class _Sentinel:
def __repr__(self):
return "<implicit>"
_sentinel = _Sentinel()
def _parse_value_tb(exc, value, tb):
if (value is _sentinel) != (tb is _sentinel):
raise ValueError("Both or neither of value and tb must be given")
if value is tb is _sentinel:
if exc is not None:
if isinstance(exc, BaseException):
return exc, exc.__traceback__
raise TypeError(f'Exception expected for value, '
f'{type(exc).__name__} found')
else:
return None, None
return value, tb
def print_exception(exc, /, value=_sentinel, tb=_sentinel, 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.
"""
value, tb = _parse_value_tb(exc, value, tb)
te = TracebackException(type(value), value, tb, limit=limit, compact=True)
te.print(file=file, chain=chain)
def format_exception(exc, /, value=_sentinel, tb=_sentinel, 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().
"""
value, tb = _parse_value_tb(exc, value, tb)
te = TracebackException(type(value), value, tb, limit=limit, compact=True)
return list(te.format(chain=chain))
def format_exception_only(exc, /, value=_sentinel):
"""Format the exception part of a traceback.
The return value is a list of strings, each ending in a newline.
The list contains the exception's message, which is
normally a single string; however, for :exc:`SyntaxError` exceptions, it
contains several lines that (when printed) display detailed information
about where the syntax error occurred. Following the message, the list
contains the exception's ``__notes__``.
"""
if value is _sentinel:
value = exc
te = TracebackException(type(value), value, None, compact=True)
return list(te.format_exception_only())
# -- not official API but folk probably use these two functions.
def _format_final_exc_line(etype, value):
valuestr = _safe_string(value, 'exception')
if value is None or not valuestr:
line = "%s\n" % etype
else:
line = "%s: %s\n" % (etype, valuestr)
return line
def _safe_string(value, what, func=str):
try:
return func(value)
except:
return f'<{what} {func.__name__}() failed>'
# --
def print_exc(limit=None, file=None, chain=True):
"""Shorthand for 'print_exception(sys.exception(), limit, file, chain)'."""
print_exception(sys.exception(), 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.exception(), limit=limit, chain=chain))
def print_last(limit=None, file=None, chain=True):
"""This is a shorthand for 'print_exception(sys.last_exc, limit, file, chain)'."""
if not hasattr(sys, "last_exc") and not hasattr(sys, "last_type"):
raise ValueError("no last exception")
if hasattr(sys, "last_exc"):
print_exception(sys.last_exc, limit, file, chain)
else:
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:
"""Information about 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', 'end_lineno', 'colno', 'end_colno',
'name', '_line', 'locals')
def __init__(self, filename, lineno, name, *, lookup_line=True,
locals=None, line=None,
end_lineno=None, colno=None, end_colno=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: _safe_string(v, 'local', func=repr)
for k, v in locals.items()} if locals else None
self.end_lineno = end_lineno
self.colno = colno
self.end_colno = end_colno
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 _original_line(self):
# Returns the line as-is from the source, without modifying whitespace.
self.line
return self._line
@property
def line(self):
if self._line is None:
if self.lineno is None:
return None
self._line = linecache.getline(self.filename, self.lineno)
return self._line.strip()
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.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
def _walk_tb_with_full_positions(tb):
# Internal version of walk_tb that yields full code positions including
# end line and column information.
while tb is not None:
positions = _get_code_position(tb.tb_frame.f_code, tb.tb_lasti)
# Yield tb_lineno when co_positions does not have a line number to
# maintain behavior with walk_tb.
if positions[0] is None:
yield tb.tb_frame, (tb.tb_lineno, ) + positions[1:]
else:
yield tb.tb_frame, positions
tb = tb.tb_next
def _get_code_position(code, instruction_index):
if instruction_index < 0:
return (None, None, None, None)
positions_gen = code.co_positions()
return next(itertools.islice(positions_gen, instruction_index // 2, None))
_RECURSIVE_CUTOFF = 3 # Also hardcoded in traceback.c.
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.
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, 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:
f_locals = None
result.append(FrameSummary(
filename, lineno, name, lookup_line=False, locals=f_locals,
end_lineno=end_lineno, colno=colno, end_colno=end_colno))
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_frame_summary(self, frame_summary):
"""Format the lines for a single FrameSummary.
Returns a string representing one frame involved in the stack. This
gets called for every frame to be printed in the stack summary.
"""
row = []
row.append(' File "{}", line {}, in {}\n'.format(
frame_summary.filename, frame_summary.lineno, frame_summary.name))
if frame_summary.line:
stripped_line = frame_summary.line.strip()
row.append(' {}\n'.format(stripped_line))
line = frame_summary._original_line
orig_line_len = len(line)
frame_line_len = len(frame_summary.line.lstrip())
stripped_characters = orig_line_len - frame_line_len
if (
frame_summary.colno is not None
and frame_summary.end_colno is not None
):
start_offset = _byte_offset_to_character_offset(
line, frame_summary.colno)
end_offset = _byte_offset_to_character_offset(
line, frame_summary.end_colno)
code_segment = line[start_offset:end_offset]
anchors = None
if frame_summary.lineno == frame_summary.end_lineno:
with suppress(Exception):
anchors = _extract_caret_anchors_from_line_segment(code_segment)
else:
# Don't count the newline since the anchors only need to
# go up until the last character of the line.
end_offset = len(line.rstrip())
# show indicators if primary char doesn't span the frame line
if end_offset - start_offset < len(stripped_line) or (
anchors and anchors.right_start_offset - anchors.left_end_offset > 0):
# When showing this on a terminal, some of the non-ASCII characters
# might be rendered as double-width characters, so we need to take
# that into account when calculating the length of the line.
dp_start_offset = _display_width(line, start_offset) + 1
dp_end_offset = _display_width(line, end_offset) + 1
row.append(' ')
row.append(' ' * (dp_start_offset - stripped_characters))
if anchors:
dp_left_end_offset = _display_width(code_segment, anchors.left_end_offset)
dp_right_start_offset = _display_width(code_segment, anchors.right_start_offset)
row.append(anchors.primary_char * dp_left_end_offset)
row.append(anchors.secondary_char * (dp_right_start_offset - dp_left_end_offset))
row.append(anchors.primary_char * (dp_end_offset - dp_start_offset - dp_right_start_offset))
else:
row.append('^' * (dp_end_offset - dp_start_offset))
row.append('\n')
if frame_summary.locals:
for name, value in sorted(frame_summary.locals.items()):
row.append(' {name} = {value}\n'.format(name=name, value=value))
return ''.join(row)
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_summary in self:
formatted_frame = self.format_frame_summary(frame_summary)
if formatted_frame is None:
continue
if (last_file is None or last_file != frame_summary.filename or
last_line is None or last_line != frame_summary.lineno or
last_name is None or last_name != frame_summary.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_summary.filename
last_line = frame_summary.lineno
last_name = frame_summary.name
count = 0
count += 1
if count > _RECURSIVE_CUTOFF:
continue
result.append(formatted_frame)
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
def _byte_offset_to_character_offset(str, offset):
as_utf8 = str.encode('utf-8')
return len(as_utf8[:offset].decode("utf-8", errors="replace"))
_Anchors = collections.namedtuple(
"_Anchors",
[
"left_end_offset",
"right_start_offset",
"primary_char",
"secondary_char",
],
defaults=["~", "^"]
)
def _extract_caret_anchors_from_line_segment(segment):
import ast
try:
tree = ast.parse(segment)
except SyntaxError:
return None
if len(tree.body) != 1:
return None
normalize = lambda offset: _byte_offset_to_character_offset(segment, offset)
statement = tree.body[0]
match statement:
case ast.Expr(expr):
match expr:
case ast.BinOp():
operator_start = normalize(expr.left.end_col_offset)
operator_end = normalize(expr.right.col_offset)
operator_str = segment[operator_start:operator_end]
operator_offset = len(operator_str) - len(operator_str.lstrip())
left_anchor = expr.left.end_col_offset + operator_offset
right_anchor = left_anchor + 1
if (
operator_offset + 1 < len(operator_str)
and not operator_str[operator_offset + 1].isspace()
):
right_anchor += 1
while left_anchor < len(segment) and ((ch := segment[left_anchor]).isspace() or ch in ")#"):
left_anchor += 1
right_anchor += 1
return _Anchors(normalize(left_anchor), normalize(right_anchor))
case ast.Subscript():
left_anchor = normalize(expr.value.end_col_offset)
right_anchor = normalize(expr.slice.end_col_offset + 1)
while left_anchor < len(segment) and ((ch := segment[left_anchor]).isspace() or ch != "["):
left_anchor += 1
while right_anchor < len(segment) and ((ch := segment[right_anchor]).isspace() or ch != "]"):
right_anchor += 1
if right_anchor < len(segment):
right_anchor += 1
return _Anchors(left_anchor, right_anchor)
return None
_WIDE_CHAR_SPECIFIERS = "WF"
def _display_width(line, offset):
"""Calculate the extra amount of width space the given source
code segment might take if it were to be displayed on a fixed
width output device. Supports wide unicode characters and emojis."""
# Fast track for ASCII-only strings
if line.isascii():
return offset
import unicodedata
return sum(
2 if unicodedata.east_asian_width(char) in _WIDE_CHAR_SPECIFIERS else 1
for char in line[:offset]
)
class _ExceptionPrintContext:
def __init__(self):
self.seen = set()
self.exception_group_depth = 0
self.need_close = False
def indent(self):
return ' ' * (2 * self.exception_group_depth)
def emit(self, text_gen, margin_char=None):
if margin_char is None:
margin_char = '|'
indent_str = self.indent()
if self.exception_group_depth:
indent_str += margin_char + ' '
if isinstance(text_gen, str):
yield textwrap.indent(text_gen, indent_str, lambda line: True)
else:
for text in text_gen:
yield textwrap.indent(text, indent_str, lambda line: True)
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.
max_group_width and max_group_depth control the formatting of exception
groups. The depth refers to the nesting level of the group, and the width
refers to the size of a single exception group's exceptions array. The
formatted output is truncated when either limit is exceeded.
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:`exceptions` For exception groups - a list of TracebackException
instances for the nested *exceptions*. ``None`` for other exceptions.
- :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:`end_lineno` For syntax errors - the end linenumber where the error
occurred. Can be `None` if not present.
- :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:`end_offset` For syntax errors - the end offset into the text where
the error occurred. Can be `None` if not present.
- :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, compact=False,
max_group_width=15, max_group_depth=10, _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__.
is_recursive_call = _seen is not None
if _seen is None:
_seen = set()
_seen.add(id(exc_value))
self.max_group_width = max_group_width
self.max_group_depth = max_group_depth
self.stack = StackSummary._extract_from_extended_frame_gen(
_walk_tb_with_full_positions(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 = _safe_string(exc_value, 'exception')
try:
self.__notes__ = getattr(exc_value, '__notes__', None)
except Exception as e:
self.__notes__ = [
f'Ignored error getting __notes__: {_safe_string(e, '__notes__', repr)}']
if exc_type and issubclass(exc_type, SyntaxError):
# Handle SyntaxError's specially
self.filename = exc_value.filename
lno = exc_value.lineno
self.lineno = str(lno) if lno is not None else None
end_lno = exc_value.end_lineno
self.end_lineno = str(end_lno) if end_lno is not None else None
self.text = exc_value.text
self.offset = exc_value.offset
self.end_offset = exc_value.end_offset
self.msg = exc_value.msg
elif exc_type and issubclass(exc_type, ImportError) and \
getattr(exc_value, "name_from", None) is not None:
wrong_name = getattr(exc_value, "name_from", None)
suggestion = _compute_suggestion_error(exc_value, exc_traceback, wrong_name)
if suggestion:
self._str += f". Did you mean: '{suggestion}'?"
elif exc_type and issubclass(exc_type, (NameError, AttributeError)) and \
getattr(exc_value, "name", None) is not None:
wrong_name = getattr(exc_value, "name", None)
suggestion = _compute_suggestion_error(exc_value, exc_traceback, wrong_name)
if suggestion:
self._str += f". Did you mean: '{suggestion}'?"
if issubclass(exc_type, NameError):
wrong_name = getattr(exc_value, "name", None)
if wrong_name is not None and wrong_name in sys.stdlib_module_names:
if suggestion:
self._str += f" Or did you forget to import '{wrong_name}'"
else:
self._str += f". Did you forget to import '{wrong_name}'"
if lookup_lines:
self._load_lines()
self.__suppress_context__ = \
exc_value.__suppress_context__ if exc_value is not None else False
# Convert __cause__ and __context__ to `TracebackExceptions`s, use a
# queue to avoid recursion (only the top-level call gets _seen == None)
if not is_recursive_call:
queue = [(self, exc_value)]
while queue:
te, e = queue.pop()
if (e and e.__cause__ is not None
and id(e.__cause__) not in _seen):
cause = TracebackException(
type(e.__cause__),
e.__cause__,
e.__cause__.__traceback__,
limit=limit,
lookup_lines=lookup_lines,
capture_locals=capture_locals,
max_group_width=max_group_width,
max_group_depth=max_group_depth,
_seen=_seen)
else:
cause = None
if compact:
need_context = (cause is None and
e is not None and
not e.__suppress_context__)
else:
need_context = True
if (e and e.__context__ is not None
and need_context and id(e.__context__) not in _seen):
context = TracebackException(
type(e.__context__),
e.__context__,
e.__context__.__traceback__,
limit=limit,
lookup_lines=lookup_lines,
capture_locals=capture_locals,
max_group_width=max_group_width,
max_group_depth=max_group_depth,
_seen=_seen)
else:
context = None
if e and isinstance(e, BaseExceptionGroup):
exceptions = []
for exc in e.exceptions:
texc = TracebackException(
type(exc),
exc,
exc.__traceback__,
limit=limit,
lookup_lines=lookup_lines,
capture_locals=capture_locals,
max_group_width=max_group_width,
max_group_depth=max_group_depth,
_seen=_seen)
exceptions.append(texc)
else:
exceptions = None
te.__cause__ = cause
te.__context__ = context
te.exceptions = exceptions
if cause:
queue.append((te.__cause__, e.__cause__))
if context:
queue.append((te.__context__, e.__context__))
if exceptions:
queue.extend(zip(te.exceptions, e.exceptions))
@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
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.
Generator yields the exception message.
For :exc:`SyntaxError` exceptions, it
also yields (before the exception message)
several lines that (when printed)
display detailed information about where the syntax error occurred.
Following the message, generator also yields
all the exception's ``__notes__``.
"""
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"):
if not isinstance(smod, str):
smod = "<unknown>"
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)
if (
isinstance(self.__notes__, collections.abc.Sequence)
and not isinstance(self.__notes__, (str, bytes))
):
for note in self.__notes__:
note = _safe_string(note, 'note')
yield from [l + '\n' for l in note.split('\n')]
elif self.__notes__ is not None:
yield "{}\n".format(_safe_string(self.__notes__, '__notes__', func=repr))
def _format_syntax_error(self, stype):
"""Format SyntaxError exceptions (internal helper)."""
# Show exactly where the problem was found.
filename_suffix = ''
if self.lineno is not None:
yield ' File "{}", line {}\n'.format(
self.filename or "<string>", self.lineno)
elif self.filename is not None:
filename_suffix = ' ({})'.format(self.filename)
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)
if self.offset is not None:
offset = self.offset
end_offset = self.end_offset if self.end_offset not in {None, 0} else offset
if offset == end_offset or end_offset == -1:
end_offset = offset + 1
# Convert 1-based column offset to 0-based index into stripped text
colno = offset - 1 - spaces
end_colno = end_offset - 1 - spaces
if colno >= 0:
# non-space whitespace (likes tabs) must be kept for alignment
caretspace = ((c if c.isspace() else ' ') for c in ltext[:colno])
yield ' {}{}'.format("".join(caretspace), ('^' * (end_colno - colno) + "\n"))
msg = self.msg or "<no detail available>"
yield "{}: {}{}\n".format(stype, msg, filename_suffix)
def format(self, *, chain=True, _ctx=None):
"""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 _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())
yield from _ctx.emit(exc.format_exception_only())
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)
yield from _ctx.emit(exc.stack.format())
yield from _ctx.emit(exc.format_exception_only())
num_excs = len(exc.exceptions)
if num_excs <= self.max_group_width:
n = num_excs
else:
n = self.max_group_width + 1
_ctx.need_close = False
for i in range(n):
last_exc = (i == n-1)
if last_exc:
# The closing frame may be added by a recursive call
_ctx.need_close = True
if self.max_group_width is not None:
truncated = (i >= self.max_group_width)
else:
truncated = False
title = f'{i+1}' if not truncated else '...'
yield (_ctx.indent() +
('+-' if i==0 else ' ') +
f'+---------------- {title} ----------------\n')
_ctx.exception_group_depth += 1
if not truncated:
yield from exc.exceptions[i].format(chain=chain, _ctx=_ctx)
else:
remaining = num_excs - self.max_group_width
plural = 's' if remaining > 1 else ''
yield from _ctx.emit(
f"and {remaining} more exception{plural}\n")
if last_exc and _ctx.need_close:
yield (_ctx.indent() +
"+------------------------------------\n")
_ctx.need_close = False
_ctx.exception_group_depth -= 1
if is_toplevel:
assert _ctx.exception_group_depth == 1
_ctx.exception_group_depth = 0
def print(self, *, file=None, chain=True):
"""Print the result of self.format(chain=chain) to 'file'."""
if file is None:
file = sys.stderr
for line in self.format(chain=chain):
print(line, file=file, end="")
_MAX_CANDIDATE_ITEMS = 750
_MAX_STRING_SIZE = 40
_MOVE_COST = 2
_CASE_COST = 1
def _substitution_cost(ch_a, ch_b):
if ch_a == ch_b:
return 0
if ch_a.lower() == ch_b.lower():
return _CASE_COST
return _MOVE_COST
def _compute_suggestion_error(exc_value, tb, wrong_name):
if wrong_name is None or not isinstance(wrong_name, str):
return None
if isinstance(exc_value, AttributeError):
obj = exc_value.obj
try:
d = dir(obj)
except Exception:
return None
elif isinstance(exc_value, ImportError):
try:
mod = __import__(exc_value.name)
d = dir(mod)
except Exception:
return None
else:
assert isinstance(exc_value, NameError)
# find most recent frame
if tb is None:
return None
while tb.tb_next is not None:
tb = tb.tb_next
frame = tb.tb_frame
d = (
list(frame.f_locals)
+ list(frame.f_globals)
+ list(frame.f_builtins)
)
# Check first if we are in a method and the instance
# has the wrong name as attribute
if 'self' in frame.f_locals:
self = frame.f_locals['self']
if hasattr(self, wrong_name):
return f"self.{wrong_name}"
# Compute closest match
if len(d) > _MAX_CANDIDATE_ITEMS:
return None
wrong_name_len = len(wrong_name)
if wrong_name_len > _MAX_STRING_SIZE:
return None
best_distance = wrong_name_len
suggestion = None
for possible_name in d:
if possible_name == wrong_name:
# A missing attribute is "found". Don't suggest it (see GH-88821).
continue
# No more than 1/3 of the involved characters should need changed.
max_distance = (len(possible_name) + wrong_name_len + 3) * _MOVE_COST // 6
# Don't take matches we've already beaten.
max_distance = min(max_distance, best_distance - 1)
current_distance = _levenshtein_distance(wrong_name, possible_name, max_distance)
if current_distance > max_distance:
continue
if not suggestion or current_distance < best_distance:
suggestion = possible_name
best_distance = current_distance
return suggestion
def _levenshtein_distance(a, b, max_cost):
# A Python implementation of Python/suggestions.c:levenshtein_distance.
# Both strings are the same
if a == b:
return 0
# Trim away common affixes
pre = 0
while a[pre:] and b[pre:] and a[pre] == b[pre]:
pre += 1
a = a[pre:]
b = b[pre:]
post = 0
while a[:post or None] and b[:post or None] and a[post-1] == b[post-1]:
post -= 1
a = a[:post or None]
b = b[:post or None]
if not a or not b:
return _MOVE_COST * (len(a) + len(b))
if len(a) > _MAX_STRING_SIZE or len(b) > _MAX_STRING_SIZE:
return max_cost + 1
# Prefer shorter buffer
if len(b) < len(a):
a, b = b, a
# Quick fail when a match is impossible
if (len(b) - len(a)) * _MOVE_COST > max_cost:
return max_cost + 1
# Instead of producing the whole traditional len(a)-by-len(b)
# matrix, we can update just one row in place.
# Initialize the buffer row
row = list(range(_MOVE_COST, _MOVE_COST * (len(a) + 1), _MOVE_COST))
result = 0
for bindex in range(len(b)):
bchar = b[bindex]
distance = result = bindex * _MOVE_COST
minimum = sys.maxsize
for index in range(len(a)):
# 1) Previous distance in this row is cost(b[:b_index], a[:index])
substitute = distance + _substitution_cost(bchar, a[index])
# 2) cost(b[:b_index], a[:index+1]) from previous row
distance = row[index]
# 3) existing result is cost(b[:b_index+1], a[index])
insert_delete = min(result, distance) + _MOVE_COST
result = min(insert_delete, substitute)
# cost(b[:b_index+1], a[:index+1])
row[index] = result
if result < minimum:
minimum = result
if minimum > max_cost:
# Everything in this row is too big, so bail early.
return max_cost + 1
return result
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