Python Array size is doubled after saving in binary format

Question

I have data stored in an array of size (4320,2160), reshaped from a list of length 4320*2160. When I save the file in binary format using numpy's tofile method, and then open the file I noticed that the array is double in length. How do I get the original values of the array? I'm assuming it has something to do with endianness, but i'm unfamiliar with dealing with it.

cdom=np.reshape(cdom, (4320,2160), order='F') # array of float values
len(cdom) # 4320*2160
cdom.tofile(filename)

arr = np.fromfile(filename, dtype=np.float32)
len(arr) # double the size of cdom: 2*4320*2160

@NathanBartley yes it is the result of the reshape. I should have been specific about that. — wxcoder
– wxcoder, Commented May 8, 2015 at 15:27
I suspect cdom has type np.float64, and you are reading the binary file as np.float32, so the length is doubled (and the values are effectively garbage). — Warren Weckesser
– Warren Weckesser, Commented May 8, 2015 at 15:33
@WarrenWeckesser You're right! Thank you! changing the dtype to float64 fixed the problem. — wxcoder
– wxcoder, Commented May 8, 2015 at 15:42

Warren Weckesser · Accepted Answer · 2015-05-08 15:45:55Z

2

It looks like cdom has type np.float64, and you are reading the binary file as np.float32, so the length is doubled (and the values are effectively garbage).

answered May 8, 2015 at 15:45

Warren Weckesser

116k20 gold badges207 silver badges224 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Python Array size is doubled after saving in binary format

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related