Convert python byte string to numpy int?

Question

Is there a direct way instead of the following?

np.uint32(int.from_bytes(b'\xa3\x8eq\xb5', 'big'))

Nathan · Accepted Answer · 2019-03-08 16:43:04Z

10

Using np.fromstring for this is deprecated now. Use np.frombuffer instead. You can also pass in a normal numpy dtype:

import numpy as np
np.frombuffer(b'\xa3\x8eq\xb5', dtype=np.uint32)

answered Mar 8, 2019 at 16:43

Nathan

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mgilson · Accepted Answer · 2015-03-11 19:49:11Z

6

The trick is to get the right datatype. To read big endian uint32 from a string the datatype (as a string) is '>u4'.

>>> np.fromstring(b'\xa3\x8eq\xb5', dtype='>u4')
array([2744021429], dtype=uint32)

This gives you an array back, but getting a scalar from there is a pretty trivial matter. More importantly, it allows you to read a large number of these objects in one go (which you can't do with your int.from_bytes trick).

answered Mar 11, 2015 at 19:49

mgilson

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2 Comments

user3467349 Over a year ago

It was just for a hash value - for which I guess there's no advantage (actually a bit slower) - but for buffers this is much better.

Eli Korvigo Over a year ago

Yeah, now I see the proper data type.

Eli Korvigo · Accepted Answer · 2015-03-11 19:47:30Z

1

I'm not sure about the data type.

np.fromstring(b'\xa3\x8eq\xb5', dtype='<i')

answered Mar 11, 2015 at 19:47

Eli Korvigo

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