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

I was looking for a solution to the same problem, then a very simple one just struck me in the head. All you need to do is decode, then re-encode. If the re-encoded string is equal to the encoded string, then it is base64 encoded.
Here is the code:

import base64  def isBase64(s):     try:         return base64.b64encode(base64.b64decode(s)) == s     except Exception:         return False 

That's it!

Edit: Here's a version of the function that works with both the string and bytes objects in Python 3:

import base64  def isBase64(sb):         try:                 if isinstance(sb, str):                         # If there's any unicode here, an exception will be thrown and the function will return false                         sb_bytes = bytes(sb, 'ascii')                 elif isinstance(sb, bytes):                         sb_bytes = sb                 else:                         raise ValueError("Argument must be string or bytes")                 return base64.b64encode(base64.b64decode(sb_bytes)) == sb_bytes         except Exception:                 return False