Check if a string is encoded in base64 using Python

Question

Is there a good way to check if a string is encoded in base64 using Python?

Answer 1

The solution I used is based on one of the prior answers, but uses more up to date calls.

In my code, the my_image_string is either the image data itself in raw form or it's a base64 string. If the decode fails, then I assume it's raw data.

Note the validate=True keyword argument to b64decode. This is required in order for the assert to be generated by the decoder. Without it there will be no complaints about an illegal string.

import base64, binascii

try:
    image_data = base64.b64decode(my_image_string, validate=True)
except binascii.Error:
    image_data = my_image_string