Count vowels in a string

Write a function count_vowels that takes a string as input and returns the number of vowels (a, e, i, o, u) in the string.

vowels = 'aeiou'
 
def count_vowels(str):

   # complete function here...

 
 
print(count_vowels('hello world')) # expected output: 3
print(count_vowels('python')) # expected output: 1

Python

Setting up Python environment...

Output