P.S: I'm new to python (and programming in general), however, I've got this question with regards to checking if a word is a palindrome. Here's my code:
def checkPal(word):
newWord = ""
for j in range(len(word)-1, 0):
newWord = newWord + word[j]
print(newWord) #this doesn't print anything
if(newWord==word):
print("Palandrome!!")
else:
print("sorry")
So this doesn't throw any errors, however, it doesn't work too! I am aware there are other ways of doing it, like:
str(n) == str(n)[::-1]
This works like a charm. But I'd just like to know what's wrong with my code. I can't seem to find a solution. I've tried item assignments separately too:
Word = ""
toAdd = "LetsTryThis"
Word = Word + toAdd[0]
print(Word)
The output:
L
The output is as expected, but this doesn't seem to work in the for loop of my checkPal function. See comment.
Thanks for the help!
If you want a range in reverse order (initial value greater than final value) you need to specify a negative step (-1 in your case)
range(5,0) # doesn't work
[]
range(5,0,-1) # works
[5, 4, 3, 2, 1]
But this is an inefficient way of reversing a string, use word[::-1] instead (will be way more efficient)
if word == word[::-1]:
print('Palindrome')
else:
print('Not a palindrome')
However if word is long, it will take a lot of effort to reverse it and then compare the whole word with the original one.
Instead you can just iterate once from 0 to len(word)/2 and compare the first element with the last one, the second with the penultimate, etc... Until one of them fail, otherwise it's a palindrome.
def is_palindrome(word):
is_palindrome = True
for i in range(len(word)/2):
if word[i] != word[-i-1]:
is_palindrome = False
break
# you can print if it's a palindrome:
if is_palindrome:
print('Palindrome')
else:
print('Not a palindrome')
# or just return a boolean answer
return is_palindrome
# test cases
is_palindrome('adda') # even palindrome
is_palindrome('adfda') # odd palindrome
is_palindrome('asda') # even non-palindrome
is_palindrome('adfsa') # odd non-palindrome