input: Write a function to generate a random password that consists of 8 characters, including uppercase and lowercase letters and digits. This function should not take any input and should return the generated password as a string.
  
  assert generate_password() is not None
  assert len(generate_password()) == 8
output: import random
  import string
  
  def generate_password():
      characters = string.ascii_letters + string.digits
      return ''.join(random.choice(characters) for _ in range(8))