Python program to Find the first non-repeating character from a stream of characters?


In this article, we will find the first non-repeating character from a stream of character. Let’s say the following is our input −

Thisisit

The following should be our output displaying first non-repeating character −

H

Find the first non-repeating character from a stream of characters using while loop

We will find the first non-repeating character, by comparing each character with the other using a loop −

Example

# String myStr = "thisisit" # Looping while myStr != "": slen0 = len(myStr) ch = myStr[0] myStr = myStr.replace(ch, "") slen1 = len(myStr) if slen1 == slen0-1: print ("First non-repeating character = ",ch) break; else: print ("No Unique Character Found!")

Output

No Unique Character Found!
First non-repeating character =  h

Find the first non-repeating character from a stream of characters using a function

We can also create a custom function and pass the string to it for finding the first non-repeating character −

Example

# Custom function def RepeatingFunc(myStr): char_order = [] counts = {} for c in myStr: if c in counts: counts[c] += 1 else: counts[c] = 1 char_order.append(c) for c in char_order: if counts[c] == 1: return c return None print("First Non-Repeating Character = ",RepeatingFunc('thisisit'))

Output

First Non-Repeating Character =  h

Find the first non-repeating character from a stream of characters using Counter()

The Counter can also be used from the Collections module to find the first non-repeating character. This module implements specialized container datatypes providing alternatives to Python’s general purpose built-in containers, dict, list, set, and tuple −

Example

from collections import Counter def repeatFunc(myStr): freq = Counter(myStr) # Traverse the string for i in myStr: if(freq[i] == 1): print(i) break # Driver code myStr = "thisisit" repeatFunc(myStr)

Output

h

Updated on: 11-Aug-2022

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