Write a python program to find the first non repeating character in given string

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

myStr = "thisisit"


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

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]

	
	for i in myStr:
	    if[freq[i] == 1]:
		    print[i]
		    break


myStr = "thisisit"

repeatFunc[myStr]

Output

h

Updated on 11-Aug-2022 11:57:47

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