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

Issue

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?

Solution

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)

Answered By - Fred Foo

Answer Checked By - Mary Flores (PHPFixing Volunteer)