Python : read array in binary file

Question

I am currently trying to read an fortran file with python with the following technique

with open(myfile, "rb") as f:
    for i in range (0, n):
        s = struct.unpack('=f', f.read(4))
        mylist.append(s[0])

But it is very slow for large arrays. Is there a way to read the content of the entire loop in one time and put it to mylist in order to avoid a conversion/append of each item one by one?

Thank you very much.

If you changed the format string from '=f' to '={}f'.format(n), you could read the entire file in with one struct.unpack() call. — martineau
– martineau, Commented Jan 29, 2013 at 17:19

interjay · Accepted Answer · 2012-02-13 11:49:04Z

12

This is what the array module is for:

a = array.array('f')
a.fromfile(f, n)

Now you can use the array object like a normal sequence type. You can also convert it to a list if you need to with tolist.

answered Feb 13, 2012 at 11:49

interjay

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