Question

Possible Duplicate:
Converting a string to and from Base 64

def convertFromBase64 (stringToBeDecoded):
    import base64
    decodedstring=str.decode('base64',"stringToBeDecoded")
    print(decodedstring)
    return

convertFromBase64(dGhpcyBpcyBzdHJpbmcgZXhhbXBsZS4uLi53b3chISE=)

I am tying to take a base64 encoded string and convert it back to the original string but I cant figure out quite what is wrong

I am getting this error

 Traceback (most recent call last):
 File "C:/Python32/junk", line 6, in <module>
convertFromBase64(("dGhpcyBpcyBzdHJpbmcgZXhhbXBsZS4uLi53b3chISE="))
 File "C:/Python32/junk", line 3, in convertFromBase64
decodedstring=str.decode('base64',"stringToBeDecoded")
AttributeError: type object 'str' has no attribute 'decode'

Answer 1

A string is already ‘decoded’, thus the str class has no ‘decode’ function.Thus:

AttributeError: type object 'str' has no attribute 'decode'

If you want to decode a byte array and turn it into a string call:

the_thing.decode(encoding)

If you want to encode a string (turn it into a byte array) call:

the_string.encode(encoding)

In terms of the base 64 stuff:
Using ‘base64’ as the value for encoding above yields the error:

LookupError: unknown encoding: base64

Open a console and type in the following:

import base64
help(base64)

You will see that base64 has two very handy functions, namely b64decode and b64encode. b64 decode returns a byte array and b64encode requires a bytes array.

To convert a string into it’s base64 representation you first need to convert it to bytes. I like utf-8 but use whatever encoding you need…

import base64
def stringToBase64(s):
    return base64.b64encode(s.encode('utf-8'))

def base64ToString(b):
    return base64.b64decode(b).decode('utf-8')