三个代码等价。with还可以很好的处理上下文环境产生的异常。
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file = open ( "/tmp/foo.txt" ) data = file .read() file .close() |
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file = open ( "/tmp/foo.txt" ) try : data = file .read() finally : file .close() |
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with open ( "/tmp/foo.txt" ) as file : data = file .read() |