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

@geoffspear is correct in that this is not 100% possible but you can get pretty close by checking the string header to see if it matches that of a base64 encoded string (re: How to check whether a string is base64 encoded or not).

# check if a string is base64 encoded.
def isBase64Encoded(s):
    pattern = re.compile("^([A-Za-z0-9+/]{4})*([A-Za-z0-9+/]{4}|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{2}==)$")
    if not s or len(s) < 1:
        return False
    else:
        return pattern.match(s)

Also not that in my case I wanted to return false if the string is empty to avoid decoding as there's no use in decoding nothing.