Why it is no working in this app?

Question

vowel = ('a', 'e', 'i', 'o', 'u')
sentence = input("Enter a sentence: ")
sentence = sentence.lower()

count = 0

for input_letter in sentence:
    if input_letter in vowel:
        count += 1
print(count)

Answer 1

In loop , remove indenation spaces and add again. Those are currently invalid characters.

Answer 2

vowel = ('a', 'e', 'i', 'o', 'u')
sentence = input()
sentence = sentence.lower()

count = 0

for input_letter in sentence:
if input_letter in vowel:
count += 1
print(count)

Answer 3

vowels = ('a', 'e', 'i', 'o', 'u')
sentence = input().lower()
print(sentence)
count = 0
for letter in sentence:
if letter in vowels:
count += 1
print(count)

In my case its working.

Answer 4

it's all about retreats. I copied the code from the PC and the app did not recognize them correctly