Question

Do files opened like file("foo.txt") have any info about file modification time?

Basically I want to know if the file has been modified or replaced since a certain time, but if the file is replaced between checking modification time and opening the file, then you have inaccurate information.

How can I be sure?

Thanks.

UPDATE

@rubayeet: Thanks for the answer (+1), I actually didn’t think of that. But… What to do if the modification time has changed? Perhaps I reload the file again. But what if it changes that time? If the file is being touched regularly I could end up in a loop forever! What I really want is a way to just get an open file handle and a modification time to go with it, without a potential infinite loop.

PS The answer you gave was actually plenty good enough for my purposes as the file won’t be changed regularly, its general interest on my part now.

UPDATE 2

Thinking the previous update through (and experimenting a little) I realize that simply knowing the file modification time at the point the file was opened is not so much use as if the file is modified while reading you can have some or all of the modified data in the stuff you read in, so you’d have to open and read/process the whole file, then check mtime again (as per @rubayeet’s answer) to see if you may have stale data.

Answer 1

import os
filepath = '/path/to/file'
modifytime1 = os.path.getmtime(filepath)
fp = open(filepath)
modifytime2 = os.path.getmtime(filepath)
if modifytime1 != modifytime2:
    print "File modified after opening"