python read(4) returning a string of length 1 not 4

I have a large binary file of ieee 32bit floating point numbers.

In python I use:

f = file.read(4)
    while f !='':
        if len(f) == 4:
            data =struct.unpack('>f', f)
            print data
f = file.read(4)

to read it 4 bytes at a time

However, occasionally f would be size 1, and struct.unpack would complain that its input must b开发者_运维问答e a string of size 4.

The filesize is divisible by 4, and this happens multiple times within the file.

What could be causing this?

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Did you open the file in binary mode?

Anyway, a much better way to read your file is to use array.fromfile() or NumPy.

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First of all, i recommend against the use of the word file as a variable, as it is a __builtin__ function.

Secondly, binary mode or ascii mode?

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See this page: file.read

Specifically

Also note that when in non-blocking mode, less data than was requested may be returned, even if no size parameter was given.