When you reach the end of the file, the readline method returns an empty string.

当到达文件末尾时，readline方法返回一个空的string。

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In case a file does not have an extension, the function returns an empty string.

对于文件没有扩展名的情况，此函数将返回空字符串。

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For paths with a single element such as c, this routine returns an empty string.

对于包含单个元素的路径，如c，此例程将返回空字符串。

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