class File:
	
	def __init__(self):
		self.valeurs = []
		
	def enfiler(self, valeur):
		self.valeurs.append(valeur)
		
	def defiler(self):
		if self.valeurs:
			return self.valeurs.pop(0)
			
	def estVide(self):
		return self.valeurs == []
		
	@property
	def longueur(self):
		return len(self.valeurs)
		
		
	def __str__(self):
		ch = "\nEtat de la file:\n"  
		for x in self.valeurs:
			ch +=  str(x) + " "    
		return ch
			
			
			
q = File()
q.enfiler(9)
q.enfiler(2)
q.enfiler(5)

print(q)

q.defiler()
q.enfiler(7)

print("La file est-elle vide: ", q.estVide())

print(q)
print("Longueur de la file:", q.longueur)