Take a look at this program.

#!/usr/bin/python

message = raw_input("Give me the word: ")
dictionary = {}
for e in message:
    if dictionary.has_key(e):
        dictionary[e] = dictionary[e] + 1
    else :
        dictionary[e] = 1
print "I have built the dictionary:"
for e in dictionary.keys():
    print "Letter " + e + " occurs " + str(dictionary[e])
letter = raw_input("Give me the letter: ")
if dictionary.has_key(letter):
    print "Letter " + letter + " occurs " + str(dictionary[letter]) + " times in " + message
else:
    print "Letter " + letter + " does not occur in " + message

print "Again:"

count = 0
for e in message:
    if letter == e:
        count = count + 1
print count
If you understand it you can assume minimal credit for this assignment.