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

x = 'possibly base64 encoded string'
result = x
try:
   decoded = x.decode('base64', 'strict')
   if x == decoded.encode('base64').strip():
       result = decoded
except:
   pass

this code put in the result variable decoded string if x is really encoded, and just x if not. Just try to decode doesn't always work.