num_vowels.py

# Write code that will count the number of vowels in the sentence s and assign the result to the variable num_vowels.
# For this problem, vowels are only a, e, i, o, and u. Hint: use the in operator with vowels.

s = "singing in the rain and playing in the rain are two entirely different situations but both can be fun"
vowels = ['a','e','i','o','u']

# Write your code here.
num_vowels = sum([1 for i in s if i in vowels])
print(num_vowels)

"""
Write code that will count the number of vowels in the sentence s and assign the result to the variable num_vowels. For this problem, vowels are only a, e, i, o, and u. Hint: use the in operator with vowels.
"""

I used generator comprehension.
In your code, you use list comprehension and then a built-in function sum.

A generator expression is like a list comprehension, but instead of finding all the items you're interested in and packing them into the list, it waits and yields each item out of the expression, one by one. Because a generator expression only has to yield one item at a time, it can lead to big savings in memory usage.
(https://stackoverflow.com/questions/364802/how-exactly-does-a-generator-comprehension-work)

s = "singing in the rain and playing in the rain are two entirely different situations but both can be fun"
vowels = ['a','e','i','o','u']
num_vowels = sum(1 for char in s if char in vowels)
print(num_vowels)

this is working good too.

s = "singing in the rain and playing in the rain are two entirely different situations but both can be fun"
vowels = ['a','e','i','o','u']
num_vowels=0
for vow in s:
for vows in vowels:
if vow==vows:
num_vowels +=1

s = "singing in the rain and playing in the rain are two entirely different situations but both can be fun"
vowels = ['a', 'e', 'i', 'o', 'u']
num_vowels = 0
s = s.split()

Write your code here.

for word in s:
for char in word:
if char in vowels:
num_vowels = num_vowels + 1

print(num_vowels)

s = "singing in the rain and playing in the rain are two entirely different situations but both can be fun"

vowels = ['a', 'e', 'i', 'o', 'u']

count = 0
for alphabet in s:
if alphabet in vowels:
count += 1
sum_vowels = count