Converting python float to bytes

NumPy arrays come with a tobytes method that gives you a dump of their raw data bytes:

arr.tobytes()

You can specify an order argument to use either C-order (row major) or F-order (column major) for multidimensional arrays.

Since you want to dump the bytes to a file, you may also be interested in the tofile method, which dumps the bytes to a file directly:

arr.tofile(your_file)

tofile always uses C-order.

If you need to change endianness, you can use the byteswap method. (newbyteorder has a more convenient signature, but doesn't change the underlying bytes, so it won't affect tobytes.)

import sys
if sys.byteorder=='big':
    arr = arr.byteswap()
data_bytes = arr.tobytes()

You could use struct to pack the bytes like,

>>> import struct
>>> struct.pack('<f', 3.14) # little-endian
b'\xc3\xf5H@'
>>> struct.pack('>f', 3.14) # big-endian
b'@H\xf5\xc3'

There are save/savez methods in numpy:

Store data to disk, and load it again:

>>> np.save('/tmp/123', np.array([[1, 2, 3], [4, 5, 6]]))
>>> np.load('/tmp/123.npy')
array([[1, 2, 3],
       [4, 5, 6]])

Store compressed data to disk, and load it again:

>>> a=np.array([[1, 2, 3], [4, 5, 6]])
>>> b=np.array([1, 2])
>>> np.savez('/tmp/123.npz', a=a, b=b)
>>> data = np.load('/tmp/123.npz')
>>> data['a']
array([[1, 2, 3],
       [4, 5, 6]])
>>> data['b']
array([1, 2])
>>> data.close()