Python での警告

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警告は、基本的に例外を発生させず、プログラムを終了しない警告メッセージです。

以下に示す警告カテゴリがあります:

Class	Disposition
Warning	This is the base class of all warning category classes. It is a subclass of Exception.
UserWarning	The default category for warn().
DeprecationWarning	Base category for warnings about deprecated features when those warnings are intended for other Python developers (ignored by default, unless triggered by code in __main__).
SyntaxWarning	Base category for warnings about dubious syntactic features.
RuntimeWarning	Base category for warnings about dubious runtime features.
FutureWarning	Base category for warnings about deprecated features when those warnings are intended for end users of applications that are written in Python.
PendingDeprecationWarning	Base category for warnings about features that will be deprecated in the future (ignored by default).
ImportWarning	Base category for warnings triggered during the process of importing a module (ignored by default).
UnicodeWarning	Base category for warnings related to Unicode.
UnicodeWarning	Base category for warnings related to Unicode.
BytesWarning	Base category for warnings related to bytes and bytearray.
ResourceWarning	Base category for warnings related to resource usage (ignored by default).

warn() は、以下に示すように手動で警告を発生させることができます。

*メモ:

• 最初の引数は message(Required-Type:str) です。
• 2 番目の引数は category(Optional-Default:None-Type:Warning) です。 *None の場合、UserWarning が設定されます。
• 3 番目の引数は stacklevel(Optional-Default:1-Type:int) です。 *警告がどのコードを参照するかを決定します。
• 4 番目の引数は、source(Optional-Default:None-Type:Any) です。
• skip_file_prefixes 引数があります (オプション-デフォルト:なし-タイプ: str のタプル): *メモ:
  • Skip_file_prefixes= を使用する必要があります。
  • 手動で None を設定するとエラーが発生します。

import warnings

warnings.warn(message="This is a warning.")
# UserWarning: This is a warning.
#   warnings.warn(message="This is a warning.")

warnings.warn(message="This is a warning.",
              category=None,
              stacklevel=1,
              source=None,
              skip_file_prefixes=())
# UserWarning: This is a warning.
#   warnings.warn(message="This is a warning.",

warnings.warn(message="This is a warning.",
              category=Warning)
# Warning: This is a warning.
#   warnings.warn(message="This is a warning.",

warnings.warn(message="This is a warning.",
              category=DeprecationWarning)
# DeprecationWarning: This is a warning.
#   warnings.warn(message="This is a warning.",

def test1():
    warnings.warn(message="Warning 1",
                  stacklevel=-100)
    warnings.warn(message="Warning 2",
                  stacklevel=0)
    warnings.warn(message="Warning 3",
                  stacklevel=1)
    warnings.warn(message="Warning 4",
                  stacklevel=2)
    warnings.warn(message="Warning 5",
                  stacklevel=3)
    warnings.warn(message="Warning 6",
                  stacklevel=4)
    warnings.warn(message="Warning 7",
                  stacklevel=5)
    warnings.warn(message="Warning 8",
                  stacklevel=100)
def test2():
    test1()

def test3():
    test2()
test3()
# UserWarning: Warning 1
#   warnings.warn(message="Warning 1",
# UserWarning: Warning 2
#   warnings.warn(message="Warning 2",
# UserWarning: Warning 3
#   warnings.warn(message="Warning 3",
# UserWarning: Warning 4
#   test1()
# UserWarning: Warning 5
#   test2()
# UserWarning: Warning 6
#   test3()
# UserWarning: Warning 7
#   exec(code_obj, self.user_global_ns, self.user_ns)
# UserWarning: Warning 8

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