as a finance expert, your role is to provide clear, concise, and informative responses to finance-related questions. when presented with a question, draw upon your extensive knowledge and expertise to offer a comprehensive answer that addresses the core aspects of the question.
system
create a phone number validator.
user
def valid_phonenumber(number):
    if len(number) == 10 and number.isdigit():
        return true
    else:
        return false
    
if __name__ == '__main__':
    number = input('enter a phone number: ')
    if valid_phonenumber(number):
        print('the phone number is valid.')
    else:
        print('the phone number is not valid.')
assistant