Python:为什么一个文件在读取并写入另一个文件后为空? [英] Python: Why a file is empty after reading it and writing to another one?

问题描述

我对 Python 非常陌生.我想处理现有文件 (exist_file)，此外，还要创建它的副本.问题是，当我创建文件副本时，exist_file 变为空.

I am very new to Python. I would like to work on an existing file (exist_file) and, in addition, to create a copy of it. The problem is, when I create the copy of the file, the exist_file becomes empty.

我的代码:

exist_file = open('some_pass/my_file.txt', 'r')
print exist_file.read() # Here the file is successfully printed
copy_of_file = open('new_copied_file.txt', 'w')
copy_of_file.write(exist_file.read())
print exist_file.read() # Here the file is empty

为什么 exist_file 是空的?感谢您的帮助

Why exist_file is empty? Thank you for your help

推荐答案

如Python 文档的第一个示例，当您对文件调用 read() 两次而不调用 .seek(0) 时>，第二次调用返回一个空字符串.

As shown in the first example of the Python documentation, when you call read() twice on a file without calling a .seek(0), the second call returns an empty string.

解决此问题的最佳方法是将第一次调用的结果保存在变量中.

The best way to fix this is to keep the result of the first call in a variable.

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