Question: 
Write a python function to count lower case letters in a given string.


Model's Code:
def lower_ctr(s):
    return sum(1 for char in s if char.islower())



Sample Correct Code:
def lower_ctr(str):
      lower_ctr= 0
      for i in range(len(str)):
          if str[i] >= 'a' and str[i] <= 'z': lower_ctr += 1     
      return  lower_ctr


Asserts:
assert lower_ctr('abc') == 3
assert lower_ctr('string') == 6
assert lower_ctr('Python') == 5


Tests:
Test 1 of 3: PASS
Test 2 of 3: PASS
Test 3 of 3: PASS

Test 818 of 974: 625/818 (76.40586797066014%): success