I have a numpy array: ch=[1, 2, 3, 4, 20, 25]
How can i write it in: b'\x01\x02\x03\x04\x14\x19'
Note: i do not want to convert each integer to binary. Is there any function available to do it directly in one step?
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ch is a numpy arraylitun bls– litun bls2021-08-09 11:12:16 +00:00Commented Aug 9, 2021 at 11:12
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import numpy as geek ch=geek.array([1, 2, 3, 4, 20, 25]) x=bytes(ch) print(x)litun bls– litun bls2021-08-09 11:12:41 +00:00Commented Aug 9, 2021 at 11:12
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2 Answers
You can use bytes bult-in and pass the sequence:
>>> ch=[1, 2, 3, 4, 20, 25]
>>> bytes(ch)
b'\x01\x02\x03\x04\x14\x19'
On a side note, what you are showing is a python list, not a numpy array.
But, if you want to operate on numpy array, you can first convert it to a python list:
>>> bytes(np.array(ch).tolist())
b'\x01\x02\x03\x04\x14\x19'
When you directly try to_bytes() on the numpy array for above data:
>>> np.array(ch).tobytes()
b'\x01\x00\x00\x00\x02\x00\x00\x00\x03\x00\x00\x00\x04\x00\x00\x00\x14\x00\x00\x00\x19\x00\x00\x00'
The above output is also right, the only difference is due to the data type, if you print it, you'll know that it's numpy.int32, which is 32 bit means 32/8=4 bytes i.e. the number of bytes required to represent each of the values.
>>> np.array(ch).dtype
dtype('int32')
If, you convert it to 8-bit i.e. 1 byte number, the output will be same, as using bytes bultin over a list:
>>> np.array(ch).astype(np.int8).tobytes()
b'\x01\x02\x03\x04\x14\x19'
6 Comments
MattDMo
This doesn't work for me. I get
b'\x01\x00\x00\x00\x02\x00\x00\x00\x03\x00\x00\x00\x04\x00\x00\x00\x14\x00\x00\x00\x19\x00\x00\x00'
ThePyGuy
Working fine on Python 3.7.5 win10
MattDMo
You're operating on a list. OP specifically indicated a NumPy array.
ThePyGuy
@MattDMo, but the input presented is not a numpy array.
litun bls
How can we chage little or big endian?
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The following will work:
b"".join([int(item).to_bytes(1, "big") for item in ch])
First you iterate over the NumPy array, convert each np.int32 object to int, call int.to_bytes() on it, returning 1 byte in big-endian order (you could also use "little" here), then joining them all together.
Alternatively, you could call list() on the array, then pass it to the built-in bytes() constructor:
bytes(list(ch))
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