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Count the number of unique characters in a string in Python
• Difficulty Level : Basic
• Last Updated : 10 Mar, 2021

Given a string S consisting of lowercase English alphabets, the task is to find the number of unique characters present in the string.

Examples:

Input: S = “geeksforgeeks”
Output: 7
Explanation: The given string “geeksforgeeks” contains 6 unique characters {‘g’, ‘e’, ‘k’, ‘s’, ‘f’, ‘o’, ‘r’}.

Input: S = “madam”
Output: 3

Approach: The idea to solve the given problem is to initialize a Set() in python to store all distinct characters of the given string and then, print the size of the set as the required answer.

Below is the implementation of the above approach:

## Python3

 `# Python program for the above approach` `# Function to count the number of distinct``# characters present in the string str``def` `countDis(``str``):` `    ``# Stores all distinct characters``    ``s ``=` `set``(``str``)` `    ``# Return the size of the set``    ``return` `len``(s)`  `# Driver Code``if` `__name__ ``=``=` `"__main__"``:` `    ``# Given string S``    ``S ``=` `"geeksforgeeks"` `    ``print``(countDis(S))`
Output:
`7`

Time Complexity: O(N)
Auxiliary Space: O(1)

#### Method 2: Using Counter function:

Count the frequencies of all elements using Counter function and number of keys of this frequency dictionary gives the result.

Below is the implementation:

## Python3

 `# Python program for the above approach``from` `collections ``import` `Counter` `# Function to count the number of distinct``# characters present in the string str``def` `countDis(``str``):` `    ``# Stores all frquencies``    ``freq ``=` `Counter(``str``)` `    ``# Return the size of the freq dictionary``    ``return` `len``(freq)`  `# Driver Code``if` `__name__ ``=``=` `"__main__"``:` `    ``# Given string S``    ``S ``=` `"geeksforgeeks"` `    ``print``(countDis(S))``    ` `# This code is contributed by vikkycirus`

Output:

`7`

Time Complexity: O(N)

Auxiliary Space: O(N)

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