convert String to MD5

Question

Ok I am trying to write a basic converter of a string to md5 hash code but when I run my program I keep getting an error that say's:

Traceback (most recent call last):
  File "C:\Users\Shane\Documents\Amer CISC\lab4.py", line 30, in <module>
    assertEqual (computeMD5hash("The quick brown fox jumps over the lazy dog"),("9e107d9d372bb6826bd81d3542a419d6"))
  File "C:\Users\Shane\Documents\Amer CISC\lab4.py", line 27, in computeMD5hash
    m.update(string)
TypeError: Unicode-objects must be encoded before hashing

My code looks like this:

def computeMD5hash(string):
    import hashlib
    from hashlib import md5
    m = hashlib.md5()
    m.update((string))
    md5string=m.digest()
    return md5string

Answer 1

As the error suggests, your string must be unicode and you have to encode it. Looking at the call you make (from your stack trace):

computeMD5hash("The quick brown fox jumps over the lazy dog")

it looks like you must be running Python 3 where strings are unicode objects. To encode to a byte representation which can then be processed by the hashlib, change this

m.update((string))

to this (if utf-8 is an appropriate encoding for you to use - it depends how you will be using this):

m.update(string.encode('utf-8'))

If this is all news to you, you should probably read the excellent Python 3 Unicode HOWTO.

---

Also, while I'm here, your code has some other issues

• some unecessary bits - no need for the from hashlib import line or the temporary md5string.
• it's bad form to import modules from within a function, so import hashlib should be moved to module scope.
• the function is returning the digest() which is raw binary, and from your stack trace it looks like you're expecting the hexdigest() instead which is the same thing represented as a hexadecimal string.

To fix and tidy it all up, try this:

import hashlib

def computeMD5hash(my_string):
    m = hashlib.md5()
    m.update(my_string.encode('utf-8'))
    return m.hexdigest()