3.12 traceback -- Print or retrieve a stack traceback 编辑
3.12 traceback -- Print or retrieve a stack traceback
This module provides a standard interface to extract, format and print stack traces of Python programs. It exactly mimics the behavior of the Python interpreter when it prints a stack trace. This is useful when you want to print stack traces under program control, such as in a ``wrapper'' around the interpreter.
The module uses traceback objects -- this is the object type that is stored in the variables sys.exc_traceback
(deprecated) and sys.last_traceback
and returned as the third item from sys.exc_info().
The module defines the following functions:
- print_tb(traceback[, limit[, file]])
- Print up to limit stack trace entries from traceback. If limit is omitted or
None
, all entries are printed. If file is omitted orNone
, the output goes tosys.stderr
; otherwise it should be an open file or file-like object to receive the output.
- print_exception(type, value, traceback[, limit[, file]])
- Print exception information and up to limit stack trace entries from traceback 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 indicating the approximate position of the error.
- print_exc([limit[, file]])
- This is a shorthand for
print_exception(sys.exc_type, sys.exc_value, sys.exc_traceback, limit, file)
. (In fact, it uses sys.exc_info() to retrieve the same information in a thread-safe way instead of using the deprecated variables.)
- print_last([limit[, file]])
- This is a shorthand for
print_exception(sys.last_type, sys.last_value, sys.last_traceback, limit, file)
.
- print_stack([f[, limit[, file]]])
- This function prints a stack trace from its invocation point. The optional f argument can be used to specify an alternate stack frame to start. The optional limit and file arguments have the same meaning as for print_exception().
- extract_tb(traceback[, limit])
- Return a list of up to limit ``pre-processed'' stack trace entries extracted from the traceback object traceback. It 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 quadruple (filename, line number, function name, text) representing the information that is usually printed for a stack trace. The text is a string with leading and trailing whitespace stripped; if the source is not available it isNone
.
- extract_stack([f[, limit]])
- 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().
- format_list(list)
- Given a list of tuples 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_exception_only(type, value)
- Format the exception part of a traceback. The arguments are the exception type and value such as given by
sys.last_type
andsys.last_value
. 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 the always last string in the list.
- format_exception(type, value, tb[, limit])
- 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_tb(tb[, limit])
- A shorthand for
format_list(extract_tb(tb, limit))
.
- format_stack([f[, limit]])
- A shorthand for
format_list(extract_stack(f, limit))
.
- tb_lineno(tb)
- This function returns the current line number set in the traceback object. This is normally the same as the
tb.tb_lineno
field of the object, but when optimization is used (the -O flag) this field is not updated correctly; this function calculates the correct value.
Subsections
如果你对这篇内容有疑问,欢迎到本站社区发帖提问 参与讨论,获取更多帮助,或者扫码二维码加入 Web 技术交流群。
绑定邮箱获取回复消息
由于您还没有绑定你的真实邮箱,如果其他用户或者作者回复了您的评论,将不能在第一时间通知您!
发布评论