ホームページ >バックエンド開発 >Python チュートリアル >% と {} プレースホルダーが混在する場合の文字列フォーマット エラーを修正するにはどうすればよいですか?
Error in String Formatting Using % and {}
While attempting to format strings using placeholders like {0}, you may encounter the error "TypeError: not all arguments converted during string formatting." This error arises due to a misunderstanding of the syntax differences between old-style % formatting and new-style {} formatting.
Old-Style % Formatting
The old-style % formatting technique employs placeholder codes% to format strings. For single values, they can be written as is:
'It will cost $%d dollars.' % 95
For multiple values, they must be supplied as a tuple:
"'%s' is longer than '%s'" % (name1, name2)
New-Style {} Formatting
The new-style {} formatting uses placeholder codes {} and the .format method. Here's the key difference: you cannot mix and match the two styles. If the "template" string contains {} placeholders, then call .format, don't use %.
'It will cost ${0} dollars.'.format(95) "'{0}' is longer than '{1}'".format(name1, name2)
Correcting the Code
To address the error in the given code, you can either use % formatting consistently or switch to {} formatting:
Old-style % Formatting
print ("'{0}' is longer than '{1}'"% (name1, name2))
New-style {} Formatting
print ("'{0}' is longer than '{1}'".format(name1, name2))
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