Python: Find the closest palindrome

Python Programming Puzzles: Exercise-93 with Solution

Write a Python program to find the closest palindrome from a given string.

Input:  
cat
Output:
cac

Input:  
madan
Output:
madam
Input: 
radivider
Output:
radividar

Input: 
madan
Output:
madam
Input: 
abc
Output:
aba

Input: 
racecbr
Output:
racecar

Sample Solution:

Python Code:

#License: https://bit.ly/3oLErEI

def test(s):
    odd = 0
    for i, c in enumerate(s):
        if c != s[~i]:
            odd += 1
    if odd % 2 == 1:
        half = odd // 2
        pal = "".join((s[i] if i < half else s[~i] for i in range(len(s))))
        return pal
    else:
        half = odd // 2
        pal = "".join((s[i] if i <= half else s[~i] for i in range(len(s))))
        return pal

s = "cat"
print("Original string:",s) 
print("Closest palindrome of the said string:")
print(test(s))
s = "madan"
print("\nOriginal string:",s) 
print("Closest palindrome of the said string:")
print(test(s))
s = "radivider"
print("Original string:",s) 
print("Closest palindrome of the said string:")
print(test(s))
s = "madan"
print("\nOriginal string:",s) 
print("Closest palindrome of the said string:")
print(test(s)) 
s = "abc"
print("Original string:",s) 
print("Closest palindrome of the said string:")
print(test(s))
s = "racecbr"
print("\nOriginal string:",s) 
print("Closest palindrome of the said string:")
print(test(s))  

Sample Output:

Original string: cat
Closest palindrome of the said string:
cac

Original string: madan
Closest palindrome of the said string:
madam
Original string: radivider
Closest palindrome of the said string:
radividar

Original string: madan
Closest palindrome of the said string:
madam
Original string: abc
Closest palindrome of the said string:
aba

Original string: racecbr
Closest palindrome of the said string:
racecar

Flowchart:

Visualize Python code execution:

The following tool visualize what the computer is doing step-by-step as it executes the said program:

Python Code Editor :

Have another way to solve this solution? Contribute your code (and comments) through Disqus.

Previous: Start with a list of integers, keep every other element in place and otherwise sort the list.
Next: Separate parentheses groups.