python中的file是什么意思呢？

是file类的构造函数,参数和内置的open()函数相同,在打开文件时更推荐使用open(),所以更多用于测试文件类型的测试:isinstance(f,file)
参考python2.7.5文档的解释:
file(name[, mode[,
buffering]])

Constructor function for the file type, described further in section File
Objects. The constructor’s arguments are the same as those of the open()
built-in function described below.

When opening a file, it’s preferable to use open()
instead of invoking this constructor directly. file
is more suited to type testing (for example, writing isinstance(f, file)).