Histogram - String - Character frequency

# Histogram - Character frequency

import operator

string1 = "An algorithm is a step-by-step procedure to solve a given problem. It is a well-defined computational procedure that takes some values as input, manipulates them using a set of instructions and produces some values as output and terminates in a finite amount of time. An algorithm, when formally written in a programming language is called a program, or code. Derivation of an algorithm that solves the problem and conversion of the algorithm into code, together,  is known as Algorithmic Problem Solving."
string1 = string1.lower()

dict1 = {}
for idx in range(97, 123, 1):
    count = string1.count(chr(idx))
    if(count != 0):
        dict1[chr(idx)] = count

print("Histogram")
print(dict1)


List1 = sorted(dict1.items(), key=operator.itemgetter(1), reverse=True)
dict2 = dict(List1[:5])
print("Most frequent 5 characters")
print(dict2)