base64 Incorrect Padding

[MRAB]

Max Erickson wrote:
> MRAB <python at mrabarnett.plus.com> wrote:
> 
>> Brandon Fredericks wrote:
>>> I did a search within this group, but couldn't find any
>>> information on this.
>>>
>>> I am sending base64 encoded data as the content over http using
>>> urllib2 urlopen. When I receive the data and attempt to decode
>>> it, I get an "Incorrect Padding" error. Is there a simple way to
>>> fix this? A better way to send and receive the data possibly
>>> (using base64 of course)?
>> Base-64 encodes 3 bytes (echo in the range 0-255) to 4 bytes
>> (each in a more restricted range). The length of the output is
>> _always_ a multiple of 4 (ignoring whitespace); the method adds
>> extra padding bytes (ASCII '=') to ensure that this is the case
>> if the length of the input isn't a multiple of 3.
>>
>> So, if decoding raises an "Incorrect Padding" error then strip
>> out any whitespace and append extra ASCII '=' to make its length
>> a multiple of 3, then try decoding again. (Or you could just
>> repeatedly add one pad character and retry, up to 3 times.)
> 
> The length of the encoded string should be a multiple of 4 (as you 
> state in the second sentence of your post), not a multiple of 3.
> 
Oops, correct! :-)