cmd = ["add","show","reset"]
def bibli(arg1):
    if arg1 is not in cmds:
        if arg1 is "add":
            bdd = open("data.txt", "a")
            while 1:
                q=input("rentrez l'url")
                if q=='stop':
                    bdd.close()
                    break
                else:
                    bdd.write(q)
                    bdd.write(" ")
        if arg1 is "show":
            bdd = open("data.txt", "a")
            print (bdd.read())
            bdd.close()
        if arg1 is "reset":
            bdd = open("data.txt", "a")
            bdd.close()