How to find out whether a file is at its `eof`?

python file eof
Alcott picture Alcott · Apr 13, 2012 · Viewed 381.3k times · Source 
fp = open("a.txt")
#do many things with fp

c = fp.read()
if c is None:
    print 'fp is at the eof'

Besides the above method, any other way to find out whether is fp is already at the eof?

Answer

Fred Foo picture Fred Foo · Apr 13, 2012

fp.read() reads up to the end of the file, so after it's successfully finished you know the file is at EOF; there's no need to check. If it cannot reach EOF it will raise an exception.

When reading a file in chunks rather than with read(), you know you've hit EOF when read returns less than the number of bytes you requested. In that case, the following read call will return the empty string (not None). The following loop reads a file in chunks; it will call read at most once too many.

assert n > 0
while True:
    chunk = fp.read(n)
    if chunk == '':
        break
    process(chunk)

Or, shorter:

for chunk in iter(lambda: fp.read(n), ''):
    process(chunk)

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