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Extract, format and print information about Python stack traces.
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.
filename = <member 'filename' of 'FrameSummary' objects>
line = <property object at 0x7f75e31ba160>
lineno = <member 'lineno' of 'FrameSummary' objects>
locals = <member 'locals' of 'FrameSummary' objects>
name = <member 'name' of 'FrameSummary' objects>
A stack of frames.
append(self, object, /) Append object to the end of the list.
clear(self, /) Remove all items from list.
copy(self, /) Return a shallow copy of the list.
count(self, value, /) Return number of occurrences of value.
extend(self, iterable, /) Extend list by appending elements from the iterable.
extract(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.
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.
from_list(a_list)
Create a StackSummary object from a supplied list of
FrameSummary objects or old-style list of tuples.
index(self, value, start=0, stop=9223372036854775807, /) Return first index of value. Raises ValueError if the value is not present.
insert(self, index, object, /) Insert object before index.
pop(self, index=-1, /) Remove and return item at index (default last). Raises IndexError if list is empty or index is out of range.
remove(self, value, /) Remove first occurrence of value. Raises ValueError if the value is not present.
reverse(self, /) Reverse *IN PLACE*.
sort(self, /, *, key=None, reverse=False) Sort the list in ascending order and return None. The sort is in-place (i.e. the list itself is modified) and stable (i.e. the order of two equal elements is maintained). If a key function is given, apply it once to each list item and sort them, ascending or descending, according to their function values. The reverse flag can be set to sort in descending order.
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:`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 offset into the text where the
error occurred. Can be `None` if not present.
- :attr:`msg` For syntax errors - the compiler error message.
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.
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.
from_exception(exc, *args, **kwargs) Create a TracebackException from an exception.
clear_frames(tb) Clear all references to local variables in the frames of a traceback.
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.
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.
format_exc(limit=None, chain=True) Like print_exc() but return a string.
format_exception(exc, /, value=<implicit>, tb=<implicit>, 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_only(exc, /, value=<implicit>)
Format the exception part of a traceback.
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.
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.
format_stack(f=None, limit=None) Shorthand for 'format_list(extract_stack(f, limit))'.
format_tb(tb, limit=None) A shorthand for 'format_list(extract_tb(tb, limit))'.
print_exc(limit=None, file=None, chain=True) Shorthand for 'print_exception(*sys.exc_info(), limit, file)'.
print_exception(exc, /, value=<implicit>, tb=<implicit>, 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.
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)'.
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.
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().
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.
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.
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.