movie = None
while movie not in ('A', 'B', 'C'):
    print('************************************************************')
print('*                                                          *')
print('*            Welcome to the cinemas                        *')
print('*                                                          *')
print('************************************************************')
print('*                                                          *')
print('*  What movie would you like to see ?                      *')
print('*                                                          *')
print('*  A) Star Wars                                            *')
print('*  B) Bourne Identity                                      *')
print('*  C) The Hunger Games                                     *')
print('*                                                          *')
print('************************************************************')
movie = input()
Циклы while для новичка в Python