Numpy Array to base64 and back to Numpy Array - Python

Question

I am now trying to figure out how I can recover a numpy array from base64 data. This question and answer suggest it is possible: Reading numpy arrays outside of Python but an example is not given.

Using the code below as an example, how can I get a Numpy array from the base64 data if I know the dtype and the shape of the array?

import base64
import numpy as np

t = np.arange(25, dtype=np.float64)
s = base64.b64encode(t)
r = base64.decodestring(s)
q = ?????

I want a python statement to set q as a numpy array of dtype float64 so the result is an array identical to t. This is what the arrays encoded and decoded look like:

>>> t = np.arange(25,dtype=np.float64)
>>> t
array([  0.,   1.,   2.,   3.,   4.,   5.,   6.,   7.,   8.,   9.,  10.,
    11.,  12.,  13.,  14.,  15.,  16.,  17.,  18.,  19.,  20.,  21.,
    22.,  23.,  24.])
>>> s=base64.b64encode(t)
>>> s
'AAAAAAAAAAAAAAAAAADwPwAAAAAAAABAAAAAAAAACEAAAAAAAAAQQAAAAAAAABRAAAAAAAAAGEAAAAAAAAAcQAAAAAAAACBAAAAAAAAAIkAAAAAAAAAkQAAAAAAAACZAAAAAAAAAKEAAAAAAAAAqQAAAAAAAACxAAAAAAAAALkAAAAAAAAAwQAAAAAAAADFAAAAAAAAAMkAAAAAAAAAzQAAAAAAAADRAAAAAAAAANUAAAAAAAAA2QAAAAAAAADdAAAAAAAAAOEA='
>>> r = base64.decodestring(s)
>>> r
'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xf0?\x00\x00\x00\x00\x00\x00\x00@\x00\x00\x00\x00\x00\x00\x08@\x00\x00\x00\x00\x00\x00\x10@\x00\x00\x00\x00\x00\x00\x14@\x00\x00\x00\x00\x00\x00\x18@\x00\x00\x00\x00\x00\x00\x1c@\x00\x00\x00\x00\x00\x00 @\x00\x00\x00\x00\x00\x00"@\x00\x00\x00\x00\x00\x00$@\x00\x00\x00\x00\x00\x00&@\x00\x00\x00\x00\x00\x00(@\x00\x00\x00\x00\x00\x00*@\x00\x00\x00\x00\x00\x00,@\x00\x00\x00\x00\x00\x00.@\x00\x00\x00\x00\x00\x000@\x00\x00\x00\x00\x00\x001@\x00\x00\x00\x00\x00\x002@\x00\x00\x00\x00\x00\x003@\x00\x00\x00\x00\x00\x004@\x00\x00\x00\x00\x00\x005@\x00\x00\x00\x00\x00\x006@\x00\x00\x00\x00\x00\x007@\x00\x00\x00\x00\x00\x008@'
>>> q = np.array( ????

The reason I am asking is because I am working on a project where I would like to store a lot of Numpy arrays in a MySQL database in an app powered by django.

Using this django snippet I can store base64 data in a textfield: http://djangosnippets.org/snippets/1669/

I want to write the arrays to the database as base64 instead of converting the arrays to a string of unicode.

user_848419 · Answer

The code below will encode it as base64. It will handle numpy arrays of any type/size without needing to remember what it was. It will also handle other arbitrary objects that can be pickled.

import numpy as np
import pickle
import codecs

obj = np.random.normal(size=(10, 10))
obj_base64string = codecs.encode(pickle.dumps(obj, protocol=pickle.HIGHEST_PROTOCOL), "base64").decode('latin1')
obj_reconstituted = pickle.loads(codecs.decode(obj_base64string.encode('latin1'), "base64"))

You can remove .decode('latin1') and .encode('latin1') if you just want the raw bytes.

Numpy Array to base64 and back to Numpy Array - Python

2 Answers