traceback
TracebackException
StackSummary
FrameSummary
atexit — 退出处理程序
atexit
源代码： Lib/traceback.py
此模块提供标准接口以提取、格式化和打印 Python 程序的堆栈跟踪。它准确模仿 Python 解释器的行为，当打印堆栈跟踪时。这很有用当想要在程序控制下打印堆栈跟踪时，譬如作为在围绕解释器的包裹器。
The module uses traceback objects — these are objects of type types.TracebackType , which are assigned to the __traceback__ 字段对于 BaseException 实例。
types.TracebackType
__traceback__
BaseException
另请参阅
faulthandler
Used to dump Python tracebacks explicitly, on a fault, after a timeout, or on a user signal.
pdb
Interactive source code debugger for Python programs.
模块定义了下列函数：
打印直到 limit stack trace entries from 回溯对象 tb (从调用者帧开始) 若 limit 为正值。否则，打印最后 abs(limit) 条目。若 limit 被省略或 None ，打印所有条目。若 file 被省略或 None ，输出转到 sys.stderr ; otherwise it should be an open file or 像文件对象 to receive the output.
abs(limit)
None
sys.stderr
3.5 版改变： 添加负值 limit 支持。
Print exception information and stack trace entries from 回溯对象 tb to file 。这不同于 print_tb() 在下列方式：
print_tb()
if tb 不是 None ，它打印头 Traceback (most recent call last):
Traceback (most recent call last):
it prints the exception type and value 在堆栈跟踪之后
if type(value) is SyntaxError and value 拥有适当格式，它打印发生句法错误的行，采用插入符号指示错误的大致位置。
SyntaxError
Since Python 3.10, instead of passing value and tb , an exception object can be passed as the first argument. If value and tb are provided, the first argument is ignored in order to provide backwards compatibility.
可选 limit 自变量有相同含义如 print_tb() 。若 chain 为 True (默认)，则连锁异常 ( __cause__ or __context__ 属性对于异常) 也将被打印，就像解释器本身在打印未处理异常时所做的。
__cause__
__context__
3.5 版改变： The etype 自变量被忽略并推断从类型对于 value .
3.10 版改变： The etype parameter has been renamed to exc and is now positional-only.
这是简写的 print_exception(sys.exception(), limit, file, chain) .
print_exception(sys.exception(), limit, file, chain)
这是简写的 print_exception(sys.last_exc, limit, file, chain) 。一般而言，它才工作在异常到达交互提示后 (见 sys.last_exc ).
print_exception(sys.last_exc, limit, file, chain)
sys.last_exc
打印直到 limit 堆栈跟踪条目 (从援引点开始) 若 limit 为正值。否则，打印最后 abs(limit) 条目。若 limit 被省略或 None ，打印所有条目。可选 f argument can be used to specify an alternate stack frame to start. The optional file 自变量有相同含义如 print_tb() .
返回 StackSummary object representing a list of “pre-processed” stack trace entries extracted from the 回溯对象 tb 。它是很有用的堆栈跟踪的替代格式。可选 limit 自变量有相同含义如 print_tb() 。"预处理" 堆栈跟踪条目是 FrameSummary object containing attributes filename , lineno , name ，和 line representing the information that is usually printed for a stack trace.
filename
lineno
name
line
Extract the raw traceback from the current stack frame . The return value has the same format as for extract_tb() 。可选 f and limit 自变量有相同含义如 print_stack() .
extract_tb()
print_stack()
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 .
extract_stack()
Format the exception part of a traceback using an exception value such as given by sys.last_value . 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 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 .
sys.last_value
notes
Since Python 3.10, instead of passing value , an exception object can be passed as the first argument. If value is provided, the first argument is ignored in order to provide backwards compatibility.
3.11 版改变： The returned list now includes any notes attached to the exception.
格式化堆栈跟踪和异常信息。自变量拥有的含义如同相应自变量在 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() .
print_exception()
3.10 版改变： This function’s behavior and signature were modified to match print_exception() .
这像 print_exc(limit) 但返回字符串而不是打印到文件。
print_exc(limit)
简写的 format_list(extract_tb(tb, limit)) .
format_list(extract_tb(tb, limit))
简写的 format_list(extract_stack(f, limit)) .
format_list(extract_stack(f, limit))
Clears the local variables of all the stack frames in a traceback tb 通过调用 clear() method of each frame object .
clear()
Added in version 3.4.
演练堆栈遵循 f.f_back from the given frame, yielding the frame and line number for each frame. If f is None , the current stack is used. This helper is used with StackSummary.extract() .
f.f_back
StackSummary.extract()
Added in version 3.5.
演练回溯遵循 tb_next yielding the frame and line number for each frame. This helper is used with StackSummary.extract() .
tb_next
模块还定义了下列类：
TracebackException objects are created from actual exceptions to capture data for later printing in a lightweight fashion.
Capture an exception for later rendering. limit , lookup_lines and capture_locals are as for the StackSummary 类。
若 compact is true, only data that is required by TracebackException ’s format() method is saved in the class attributes. In particular, the __context__ field is calculated only if __cause__ is None and __suppress_context__ 为 False。
format()
__suppress_context__
Note that when locals are captured, they are also shown in the traceback.
max_group_width and max_group_depth control the formatting of exception groups (see BaseExceptionGroup ). 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.
BaseExceptionGroup
3.10 版改变： 添加 compact 参数。
3.11 版改变： 添加 max_group_width and max_group_depth 参数。
A TracebackException of the original __cause__ .
A TracebackException of the original __context__ .
若 self represents an ExceptionGroup , this field holds a list of TracebackException instances representing the nested exceptions. Otherwise it is None .
self
ExceptionGroup
Added in version 3.11.
The __suppress_context__ value from the original exception.
The __notes__ value from the original exception, or None if the exception does not have any notes. If it is not None is it formatted in the traceback after the exception string.
__notes__
A StackSummary representing the traceback.
原始回溯的类。
For syntax errors - the file name where the error occurred.
For syntax errors - the line number where the error occurred.
For syntax errors - the end line number where the error occurred. Can be None if not present.
Added in version 3.10.
For syntax errors - the text where the error occurred.
For syntax errors - the offset into the text where the error occurred.
For syntax errors - the end offset into the text where the error occurred. Can be None if not present.
For syntax errors - the compiler error message.
Print to file (默认 sys.stderr ) the exception information returned by format() .
Format the exception.
若 chain 不是 True , __cause__ and __context__ will not be formatted.
True
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.
Format the exception part of the traceback.
The return value is a generator of strings, each ending in a newline.
The generator emits the exception’s message followed by its notes (if it has any). The exception message is normally a single string; however, for SyntaxError exceptions, it consists of several lines that (when printed) display detailed information about where the syntax error occurred.
3.11 版改变： The exception’s notes are now included in the output.
StackSummary objects represent a call stack ready for formatting.
构造 StackSummary object from a frame generator (such as is returned by walk_stack() or walk_tb() ).
walk_stack()
walk_tb()
若 limit is supplied, only this many frames are taken from frame_gen 。若 lookup_lines is False , the returned FrameSummary objects will not have read their lines in yet, making the cost of creating the StackSummary cheaper (which may be valuable if it may not actually get formatted). If capture_locals is True the local variables in each FrameSummary are captured as object representations.
False
Changed in version 3.12: Exceptions raised from repr() on a local variable (when capture_locals is True ) are no longer propagated to the caller.
repr()
构造 StackSummary object from a supplied list of FrameSummary objects or old-style list of tuples. Each tuple should be a 4-tuple with filename , lineno , name , line as the elements.
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.
3.6 版改变： Long sequences of repeated frames are now abbreviated.
Returns a string for printing one of the frames involved in the stack. This method is called for each FrameSummary object to be printed by StackSummary.format() 。若它返回 None , the frame is omitted from the output.
StackSummary.format()
A FrameSummary object represents a single frame 在 traceback .
Represents a single frame 在 traceback or stack that is being formatted or printed. It may optionally have a stringified version of the frame’s locals included in it. If lookup_line is False , the source code is not looked up until the FrameSummary 拥有 line attribute accessed (which also happens when casting it to a tuple ). line may be directly provided, and will prevent line lookups happening at all. locals is an optional local variable dictionary, and if supplied the variable representations are stored in the summary for later display.
tuple
FrameSummary 实例拥有下列属性：
The filename of the source code for this frame. Equivalent to accessing f.f_code.co_filename 在 frame object f .
f.f_code.co_filename
The line number of the source code for this frame.
Equivalent to accessing f.f_code.co_name 在 frame object f .
f.f_code.co_name
A string representing the source code for this frame, with leading and trailing whitespace stripped. If the source is not available, it is None .
This simple example implements a basic read-eval-print loop, similar to (but less useful than) the standard Python interactive interpreter loop. For a more complete implementation of the interpreter loop, refer to the code 模块。
code
import sys, traceback def run_user_code(envdir): source = input(">>> ") try: exec(source, envdir) except Exception: print("Exception in user code:") print("-"*60) traceback.print_exc(file=sys.stdout) print("-"*60) envdir = {} while True: run_user_code(envdir)
The following example demonstrates the different ways to print and format the exception and traceback:
import sys, traceback def lumberjack(): bright_side_of_life() def bright_side_of_life(): return tuple()[0] try: lumberjack() except IndexError: exc = sys.exception() print("*** print_tb:") traceback.print_tb(exc.__traceback__, limit=1, file=sys.stdout) print("*** print_exception:") traceback.print_exception(exc, limit=2, file=sys.stdout) print("*** print_exc:") traceback.print_exc(limit=2, file=sys.stdout) print("*** format_exc, first and last line:") formatted_lines = traceback.format_exc().splitlines() print(formatted_lines[0]) print(formatted_lines[-1]) print("*** format_exception:") print(repr(traceback.format_exception(exc))) print("*** extract_tb:") print(repr(traceback.extract_tb(exc.__traceback__))) print("*** format_tb:") print(repr(traceback.format_tb(exc.__traceback__))) print("*** tb_lineno:", exc.__traceback__.tb_lineno)
The output for the example would look similar to this:
*** print_tb: File "<doctest...>", line 10, in <module> lumberjack() *** print_exception: Traceback (most recent call last): File "<doctest...>", line 10, in <module> lumberjack() File "<doctest...>", line 4, in lumberjack bright_side_of_life() IndexError: tuple index out of range *** print_exc: Traceback (most recent call last): File "<doctest...>", line 10, in <module> lumberjack() File "<doctest...>", line 4, in lumberjack bright_side_of_life() IndexError: tuple index out of range *** format_exc, first and last line: Traceback (most recent call last): IndexError: tuple index out of range *** format_exception: ['Traceback (most recent call last):\n', ' File "<doctest default[0]>", line 10, in <module>\n lumberjack()\n', ' File "<doctest default[0]>", line 4, in lumberjack\n bright_side_of_life()\n', ' File "<doctest default[0]>", line 7, in bright_side_of_life\n return tuple()[0]\n ~~~~~~~^^^\n', 'IndexError: tuple index out of range\n'] *** extract_tb: [<FrameSummary file <doctest...>, line 10 in <module>>, <FrameSummary file <doctest...>, line 4 in lumberjack>, <FrameSummary file <doctest...>, line 7 in bright_side_of_life>] *** format_tb: [' File "<doctest default[0]>", line 10, in <module>\n lumberjack()\n', ' File "<doctest default[0]>", line 4, in lumberjack\n bright_side_of_life()\n', ' File "<doctest default[0]>", line 7, in bright_side_of_life\n return tuple()[0]\n ~~~~~~~^^^\n'] *** tb_lineno: 10
The following example shows the different ways to print and format the stack:
>>> import traceback >>> def another_function(): ... lumberstack() ... >>> def lumberstack(): ... traceback.print_stack() ... print(repr(traceback.extract_stack())) ... print(repr(traceback.format_stack())) ... >>> another_function() File "<doctest>", line 10, in <module> another_function() File "<doctest>", line 3, in another_function lumberstack() File "<doctest>", line 6, in lumberstack traceback.print_stack() [('<doctest>', 10, '<module>', 'another_function()'), ('<doctest>', 3, 'another_function', 'lumberstack()'), ('<doctest>', 7, 'lumberstack', 'print(repr(traceback.extract_stack()))')] [' File "<doctest>", line 10, in <module>\n another_function()\n', ' File "<doctest>", line 3, in another_function\n lumberstack()\n', ' File "<doctest>", line 8, in lumberstack\n print(repr(traceback.format_stack()))\n']
This last example demonstrates the final few formatting functions:
>>> import traceback >>> traceback.format_list([('spam.py', 3, '<module>', 'spam.eggs()'), ... ('eggs.py', 42, 'eggs', 'return "bacon"')]) [' File "spam.py", line 3, in <module>\n spam.eggs()\n', ' File "eggs.py", line 42, in eggs\n return "bacon"\n'] >>> an_error = IndexError('tuple index out of range') >>> traceback.format_exception_only(type(an_error), an_error) ['IndexError: tuple index out of range\n']
__future__ — 未来的语句定义
__future__
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