Python 3:如何检查文件是否打开?Python等价于C++ifstream.is_open()函数

Question

在Python3中打开文件后，如何检查文件是否已正确打开？

with open("filename" as f:
# check that file is opened correctly here

C++CCD_ 1为此提供了CCD_ 2函数。有没有相当于C++ifstream::is_open()函数的Python？

在C中，一个人会做

FILE *fd = fopen(...)
if(fd != NULL) ...

Answer 1

f = open('file.txt')
if f.closed:
print 'file is closed'
if not f.closed:
print 'file is opened'