traceback
--- Print or retrieve a stack traceback¶
ソースコード: Lib/traceback.py
このモジュールは Python プログラムのスタックトレースを抽出し、書式を整え、表示するための標準インターフェースを提供します。モジュールがスタックトレースを表示するとき、Python インタープリタの動作を正確に模倣します。インタープリタの"ラッパー"の場合のように、プログラムの制御の元でスタックトレースを表示したいと思ったときに役に立ちます。
The module uses traceback objects --- these are
objects of type types.TracebackType
,
which are assigned to the __traceback__
field of
BaseException
instances.
参考
faulthandler
モジュールUsed to dump Python tracebacks explicitly, on a fault, after a timeout, or on a user signal.
- Module
pdb
Interactive source code debugger for Python programs.
このモジュールには、以下の関数が定義されています:
- traceback.print_tb(tb, limit=None, file=None)¶
Print up to limit stack trace entries from traceback object tb (starting from the caller's frame) if limit is positive. Otherwise, print the last
abs(limit)
entries. If limit is omitted orNone
, 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.バージョン 3.5 で変更: 負の limit がサポートされました。
- traceback.print_exception(exc, /, [value, tb, ]limit=None, file=None, chain=True)¶
Print exception information and stack trace entries from traceback object tb to file. This differs from
print_tb()
in the following ways:tb が
None
でない場合ヘッダTraceback (most recent call last):
を出力しますit prints the exception type and value after the stack trace
type(value) が
SyntaxError
であり、 value が適切な形式を持っていれば、そのエラーのおおよその位置を示すマークと共にシンタックスエラーが発生した行が表示されます。
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.
The optional limit argument has the same meaning as for
print_tb()
. If chain is true (the default), then chained exceptions (the__cause__
or__context__
attributes of the exception) will be printed as well, like the interpreter itself does when printing an unhandled exception.バージョン 3.5 で変更: 引数 etype は無視され、 value の型から推論されます。
バージョン 3.10 で変更: The etype parameter has been renamed to exc and is now positional-only.
- traceback.print_exc(limit=None, file=None, chain=True)¶
print_exception(sys.exception(), limit, file, chain)
の省略表現です。
- traceback.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, chain)
. In general it will work only after an exception has reached an interactive prompt (seesys.last_type
).
- traceback.print_stack(f=None, limit=None, file=None)¶
Print up to limit stack trace entries (starting from the invocation point) if limit is positive. Otherwise, print the last
abs(limit)
entries. If limit is omitted orNone
, all entries are printed. The optional f argument can be used to specify an alternate stack frame to start. The optional file argument has the same meaning as forprint_tb()
.バージョン 3.5 で変更: 負の limit がサポートされました。
- traceback.extract_tb(tb, limit=None)¶
Return a
StackSummary
object representing a list of "pre-processed" stack trace entries extracted from the traceback object tb. It is useful for alternate formatting of stack traces. The optional limit argument has the same meaning as forprint_tb()
. A "pre-processed" stack trace entry is aFrameSummary
object containing attributesfilename
,lineno
,name
, andline
representing the information that is usually printed for a stack trace.
- 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 forprint_stack()
.
- traceback.format_list(extracted_list)¶
extract_tb()
またはextract_stack()
が返すタプルのリストまたはFrameSummary
オブジェクトが与えられると、出力の準備を整えた文字列のリストを返します。結果として生じるリストの中の各文字列は、引数リストの中の同じインデックスの要素に対応します。各文字列は末尾に改行が付いています。さらに、ソーステキスト行がNone
でないそれらの要素に対しては、文字列は内部に改行を含んでいるかもしれません。
- traceback.format_exception_only(exc, /[, value])¶
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, forSyntaxError
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'snotes
.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.
バージョン 3.10 で変更: The etype parameter has been renamed to exc and is now positional-only.
バージョン 3.11 で変更: The returned list now includes any
notes
attached to the exception.
- traceback.format_exception(exc, /, [value, tb, ]limit=None, chain=True)¶
スタックトレースと例外情報を書式化します。引数は
print_exception()
の対応する引数と同じ意味を持ちます。戻り値は文字列のリストで、それぞれの文字列は改行で終わり、そのいくつかは内部に改行を含みます。これらの行が連結されて出力される場合は、厳密にprint_exception()
と同じテキストが出力されます。バージョン 3.5 で変更: 引数 etype は無視され、 value の型から推論されます。
バージョン 3.10 で変更: This function's behavior and signature were modified to match
print_exception()
.
- traceback.format_exc(limit=None, chain=True)¶
これは、
print_exc(limit)
に似ていますが、ファイルに出力する代わりに文字列を返します。
- traceback.format_tb(tb, limit=None)¶
format_list(extract_tb(tb, limit))
の省略表現です。
- traceback.format_stack(f=None, limit=None)¶
format_list(extract_stack(f, limit))
の省略表現です。
- traceback.clear_frames(tb)¶
Clears the local variables of all the stack frames in a traceback tb by calling the
clear()
method of each frame object.バージョン 3.4 で追加.
- traceback.walk_stack(f)¶
Walk a stack following
f.f_back
from the given frame, yielding the frame and line number for each frame. If f isNone
, the current stack is used. This helper is used withStackSummary.extract()
.バージョン 3.5 で追加.
- traceback.walk_tb(tb)¶
Walk a traceback following
tb_next
yielding the frame and line number for each frame. This helper is used withStackSummary.extract()
.バージョン 3.5 で追加.
このモジュールは以下のクラスも定義しています:
TracebackException
オブジェクト¶
バージョン 3.5 で追加.
TracebackException
objects are created from actual exceptions to
capture data for later printing in a lightweight fashion.
- class traceback.TracebackException(exc_type, exc_value, exc_traceback, *, limit=None, lookup_lines=True, capture_locals=False, compact=False, max_group_width=15, max_group_depth=10)¶
後のレンダリングのために例外をキャプチャします。 limit、lookup_lines、capture_locals は
StackSummary
class のものです。If compact is true, only data that is required by
TracebackException
'sformat()
method is saved in the class attributes. In particular, the__context__
field is calculated only if__cause__
isNone
and__suppress_context__
is false.局所変数がキャプチャされたとき、それらはトレースバックに表示されることに注意してください。
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.バージョン 3.10 で変更: compact 引数が追加されました。
バージョン 3.11 で変更: Added the max_group_width and max_group_depth parameters.
- __context__¶
A
TracebackException
of the original__context__
.
- exceptions¶
If
self
represents anExceptionGroup
, this field holds a list ofTracebackException
instances representing the nested exceptions. Otherwise it isNone
.バージョン 3.11 で追加.
- __suppress_context__¶
The
__suppress_context__
value from the original exception.
- __notes__¶
The
__notes__
value from the original exception, orNone
if the exception does not have any notes. If it is notNone
is it formatted in the traceback after the exception string.バージョン 3.11 で追加.
- stack¶
トレースバックを表す
StackSummary
。
- exc_type¶
元々のトレースバックのクラス。
- filename¶
構文エラー用 - エラーが発生したファイルの名前。
- lineno¶
構文エラー用 - エラーが発生した行番号。
- end_lineno¶
For syntax errors - the end line number where the error occurred. Can be
None
if not present.バージョン 3.10 で追加.
- text¶
構文エラー用 - エラーが発生したテクスト。
- offset¶
構文エラー用 - エラーが発生したテクストへのオフセット。
- end_offset¶
For syntax errors - the end offset into the text where the error occurred. Can be
None
if not present.バージョン 3.10 で追加.
- msg¶
構文エラー用 - コンパイラのエラーメッセージ。
- classmethod from_exception(exc, *, limit=None, lookup_lines=True, capture_locals=False)¶
後のレンダリングのために例外をキャプチャします。 limit、lookup_lines、capture_locals は
StackSummary
class のものです。局所変数がキャプチャされたとき、それらはトレースバックに表示されることに注意してください。
- print(*, file=None, chain=True)¶
Print to file (default
sys.stderr
) the exception information returned byformat()
.バージョン 3.11 で追加.
- format(*, chain=True)¶
例外を書式化します。
If chain is not
True
,__cause__
and__context__
will not be formatted.返り値は文字列のジェネレータで、それぞれ改行で終わりますが、内部に改行を持つものもあります。
print_exception()
はこのメソッドのラッパで、単にファイルに出力します。
- format_exception_only()¶
トレースバックの例外部を書式化します。
返り値は文字列のジェネレータで、それぞれ改行で終わります。
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.バージョン 3.11 で変更: The exception's
notes
are now included in the output.
StackSummary
オブジェクト¶
バージョン 3.5 で追加.
StackSummary
objects represent a call stack ready for formatting.
- class traceback.StackSummary¶
- classmethod extract(frame_gen, *, limit=None, lookup_lines=True, capture_locals=False)¶
Construct a
StackSummary
object from a frame generator (such as is returned bywalk_stack()
orwalk_tb()
).If limit is supplied, only this many frames are taken from frame_gen. If lookup_lines is
False
, the returnedFrameSummary
objects will not have read their lines in yet, making the cost of creating theStackSummary
cheaper (which may be valuable if it may not actually get formatted). If capture_locals isTrue
the local variables in eachFrameSummary
are captured as object representations.
- classmethod from_list(a_list)¶
Construct a
StackSummary
object from a supplied list ofFrameSummary
objects or old-style list of tuples. Each tuple should be a 4-tuple with filename, lineno, name, line as the elements.
- format()¶
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.
バージョン 3.6 で変更: Long sequences of repeated frames are now abbreviated.
- format_frame_summary(frame_summary)¶
Returns a string for printing one of the frames involved in the stack. This method is called for each
FrameSummary
object to be printed byStackSummary.format()
. If it returnsNone
, the frame is omitted from the output.バージョン 3.11 で追加.
FrameSummary
オブジェクト¶
バージョン 3.5 で追加.
A FrameSummary
object represents a single frame
in a traceback.
- class traceback.FrameSummary(filename, lineno, name, lookup_line=True, locals=None, line=None)¶
Represents a single frame in the 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 theFrameSummary
has theline
attribute accessed (which also happens when casting it to atuple
).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.FrameSummary
instances have the following attributes:- filename¶
The filename of the source code for this frame. Equivalent to accessing
f.f_code.co_filename
on a frame object f.
- lineno¶
The line number of the source code for this frame.
- name¶
Equivalent to accessing
f.f_code.co_name
on a frame object f.
- line¶
A string representing the source code for this frame, with leading and trailing whitespace stripped. If the source is not available, it is
None
.
トレースバックの例¶
この簡単な例では基本的な read-eval-print ループを実装しています。標準的な Python の対話インタープリタループに似ていますが、 Python のものより便利ではありません。インタープリタループのより完全な実装については、 code
モジュールを参照してください。
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)
次の例は例外とトレースバックの出力並びに形式が異なることを示します:
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)
この例の出力は次のようになります:
*** 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
次の例は、スタックの print と format の違いを示しています:
>>> 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']
最後の例は、残りの幾つかの関数のデモをします:
>>> 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']