AttributeError: 'module' object has no attribute 'a'

Question

I am trying to learn python and trying to write a simple script. There seems to be a problem with using a raw_input created variable. I am sure it's simple, but I just don't have the background yet to figure this one out. Here is what I've tried and what works:

#!/usr/bin/python

import hashlib

v = raw_input("Enter your value: ")
print "Which hash algorithm do you want to use?"
# This fails
a = raw_input("md5, sha1, sha224, sha256, sha384, sha512: ")
h = hashlib.a(v)
h.hexdigest()

# This works

v = "password"
h = hashlib.md5(v)
h.hexdigest()

Answer 1

a is just storing a variable with a string value. hashlib.a() is just trying to call a method called a in the hashlib module (which doesnt exist). Try instead using

h = haslib.new(a)
h.update(v)
h.hexdigest()

Answer 2

hashes = ("md5", "sha1", "sha224", "sha256", "sha384", "sha512")

chosen_hash = None

while not chosen_hash:
    try_hash = raw_input("%s: " % (",".join(hashes))
    if try_hash in hashes:
        chosen_hash = try_hash

hash_func = getattr(hashlib, chosen_hash)()
hash_func.update(v)

As @gos1 suggested, you might use hashlib.new(chosen_hash) instead.

The nice thing is this will guard against someone entering foo as their choice and having your program blow up.