class File :
    def __init__ ( self) :
        self.contenu = []

    def ajout(self, a) :
        self.contenu.append(a)
    
    def file_vide(self):
        return len(self.contenu) == 0
    
    def retire(self):
        return self.contenu.pop(0)
        
    def lire_debut(self):
        return self.contenu[0]