I've been trying the Spy life code coach question. But I just can't seem to get it right. What is wrong with my code?

Question

word = input()

rev_word = word[::-1]
rev_word = list(rev_word)

valid = "a b c d e f g h i j k l m n o p q r s t u v w x y z A B C D E F G H I J K L M N O P Q R S T U V W X Y Z"
valid = list(valid)

for i in rev_word:
if not i in valid:
rev_word.remove(i)

rev_word = "".join(rev_word)

print(rev_word)

Answer 1

Umar Muhammad ,

the task description says that we have to remove all "none" alphabet character. as Jayakrishna🇮🇳 already mentioned, iterating and removing elements at the same time can create issues. so we can go for an other strategy and try this (we are going to create a new string that contains only allowed characters):

> input the string and then reverse it

> create an empty list that can hold the characters after "filtering" out not allowed characters

> run a loop over the reversed string, it will give you one character in each iteration cycle
> check if the character is allowed:
this can be done by using the string method isxxxx() that checks for alphabet characters, check also if character is a space
if char is alpha or a space, append this character to the list

> if iteration of the loop is done, the list contains only allowed characters

> finally we have to join the list elements to a string and the output it.

Answer 2

Umar Muhammad ,

your solution is perfect 👍😁

Answer 3

in loop, for I in rev_word: you are using original list, so removing will reflect on next iteration value.
a1cb => if you remove 1, next element is for i value is b, not c because list str is acb.

Answer 4

Lothar thank you. I'll try these

Answer 5

As @Lother said, use isalpha() , (isspace() ) instead of 'valid' list. If true add to empty list.
You code works well if you use rev_word.copy() instead of rev_word in loop.
You're welcome...

Answer 6

Solved it!
word = input()

rev_word = word[::-1]
rev_word = list(rev_word)

out_word = []

for i in rev_word:
if i.isalpha() or i.isspace():
out_word.append(i)

out_word= "".join(out_word)

print(out_word)

Answer 7

Jayakrishna🇮🇳 Thank you so much