input: Write a python function to generate a random password of a given length containing uppercase letters, lowercase letters, and digits.
  assert len(generate_random_password(12)) == 12
  assert len(generate_random_password(8)) == 8
  assert len(generate_random_password(16)) == 16
output: import random
  import string
  
  def generate_random_password(length):
      if length < 1:
          return ""
      
      all_characters = string.ascii_letters + string.digits
      password = ''.join(random.choice(all_characters) for _ in range(length))
      
      return password