Python program to Replace all Characters of a List Except the given character

Given a List. The task is to replace all the characters of the list with N except the given character.

Input : test_list = [‘G’, ‘F’, ‘G’, ‘I’, ‘S’, ‘B’, ‘E’, ‘S’, ‘T’], repl_chr = ‘*’, ret_chr = ‘G’ 
Output : [‘G’, ‘*’, ‘G’, ‘*’, ‘*’, ‘*’, ‘*’, ‘*’, ‘*’] 
Explanation : All characters except G replaced by *

Input : test_list = [‘G’, ‘F’, ‘G’, ‘B’, ‘E’, ‘S’, ‘T’], repl_chr = ‘*’, ret_chr = ‘G’ 
Output : [‘G’, ‘*’, ‘G’, ‘*’, ‘*’, ‘*’, ‘*’] 
Explanation : All characters except G replaced by * 

Method #1 : Using list comprehension + conditional expressions

In this, we perform the task of iteration using list comprehension, and replacements are taken care of using conditional operators.

Python3

# Python3 code to demonstrate working of
# Replace all Characters Except K
# Using list comprehension and conditional expressions

# initializing lists
test_list = ['G', 'F', 'G', 'I', 'S', 'B', 'E', 'S', 'T']

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

# initializing repl_chr
repl_chr = '$'

# initializing retain chararter
ret_chr = 'G'

# list comprehension to remake list after replacement
res = [ele if ele == ret_chr else repl_chr for ele in test_list]

# printing result
print("List after replacement : " + str(res))

Output

The original list : ['G', 'F', 'G', 'I', 'S', 'B', 'E', 'S', 'T']
List after replacement : ['G', '$', 'G', '$', '$', '$', '$', '$', '$']

Method #2 : Using map() + lambda

In this, we use map() and lambda function to extend the logic to each element of the list.

Python3

# Python3 code to demonstrate working of
# Replace all Characters Except K
# Using map() + lambda

# initializing lists
test_list = ['G', 'F', 'G', 'I', 'S', 'B', 'E', 'S', 'T']

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

# initializing repl_chr
repl_chr = '$'

# initializing retain chararter
ret_chr = 'G'

# using map() to extend logic to each element of list
res = list(map(lambda ele: ret_chr if ele == ret_chr else repl_chr, test_list))

# printing result
print("List after replacement : " + str(res))

Output

The original list : ['G', 'F', 'G', 'I', 'S', 'B', 'E', 'S', 'T']
List after replacement : ['G', '$', 'G', '$', '$', '$', '$', '$', '$']