input: from typing import List
  
  def num_common_chars(str1: str, str2: str) -> int:
      """ Given two strings, find the total number of common characters present in both strings.
      >>> num_common_chars("hello", "world")
      3
      >>> num_common_chars("apple", "orange")
      2
      >>> num_common_chars("abc", "def")
      0
      """
      common = 0
      for c in str1:
          if c in str2:
              common += 1
      return common
output:     common = 0
      for c in str1:
          if c in str2:
              common += 1
              str2 = str2.replace(c, '', 1)
      return common