Python – Case Insensitive string counter

Given a list of strings, find the frequency of strings case insensitive.

Input : test_list = ["Gfg", "Best", "GFG", "is", "IS", "BEST"] 
Output : {'gfg': 2, 'best': 2, 'is': 2} 
Explanation : All occur twice. 

Input : test_list = ["Gfg", "gfg", "GFG"] 
Output : {'gfg': 3} 
Explanation : Only "gfg" 3 occurrences.

Method 1: Using defaultdict() + lower()

In this, we perform lower() to all the strings, before mapping in defaultdict. This ensures case insensitivity while mapping and cumulating frequency.

Python3

# Python3 code to demonstrate working of
# Strings Frequency (Case Insensitive)
# Using defaultdict() + lower()

from collections import defaultdict

# initializing list
test_list = ["Gfg", "Best", "best", "gfg", "GFG", "is", "IS", "BEST"]

# printing original list
print("The original list is : " + str(test_list))

res = defaultdict(int)

for ele in test_list:

    # lowercasing to cater for Case Insensitivity
    res[ele.lower()] += 1

# printing result
print("Strings Frequency : " + str(dict(res)))

Output

The original list is : ['Gfg', 'Best', 'best', 'gfg', 'GFG', 'is', 'IS', 'BEST']
Strings Frequency : {'gfg': 3, 'best': 3, 'is': 2}

Time Complexity: O(n)

Auxiliary Space: O(n) 

Method 2: Using count() method

Python3

# Python3 code to demonstrate working of
# Strings Frequency (Case Insensitive)

# initializing list
test_list = ["Gfg", "Best", "best", "gfg", "GFG", "is", "IS", "BEST"]

# printing original list
print("The original list is : " + str(test_list))
x = []
res = dict()
for i in test_list:
    x.append(i.lower())
a = list(set(x))
for i in a:
    res[i] = x.count(i)

# printing result
print("Strings Frequency : " + str(dict(res)))

Output

The original list is : ['Gfg', 'Best', 'best', 'gfg', 'GFG', 'is', 'IS', 'BEST']
Strings Frequency : {'best': 3, 'is': 2, 'gfg': 3}