input: Write a function to generate a random password consisting of 8 characters. The password should include both letters (uppercase and lowercase) and digits.
  import string
  import random
  
  def generate_password():
      chars = string.ascii_letters + string.digits
      return ''.join(random.choice(chars) for _ in range(8))
  
  assert len(generate_password()) == 8
  assert any(c.isdigit() for c in generate_password())
  assert any(c.islower() for c in generate_password())
  assert any(c.isupper() for c in generate_password())
  assert not all(c.isdigit() for c in generate_password())
output: import string
  import random
  
  def generate_password():
      chars = string.ascii_letters + string.digits
      return ''.join(random.choice(chars) for _ in range(8))