Python Phone Class — printing None

问题

class Phone:
    def __init__(self):
        self.types = ["Touch Screen","Flip", "Slider", "Bar", "Bag"]
        self.brand = "No Brand Determined"
        self.type_of_phone = "No Type of Phone has been selected"

    def get_type(self):
        return self.type_of_phone
    def change_type(self, changeTo):
        if self.check_type(changeTo):
            self.type_of_phone = changeTo
        else:
            print("The Type you wish to change the phone to is not a supported type.")

    def change_brand(self, changeTo):
        self.brand = changeTo


    def check_type(self, inQuestion):
        if inQuestion in self.types:
            return True
        return False
    def toString(self):
        return "Brand: "+self.brand+"\nType: "+self.type_of_phone+"\n"

    def menu(self):
        self.intro()
        while True:
            self.mainScreen()

    def intro(self):
        print("This program will let you create a cell phone type and brand.")

    def mainScreen(self):
        option = input(print("(1) See your phone specs \n(2) Change information\n Enter a Number: "))
        if option == "1":
            print("\n"+self.toString())
        elif option == "2":
            self.changeScreen()
        else:
            print("Enter 1 or 2. Please.")

    def changeScreen(self):
            option = input(print("\nWould you like to change the...\n(1) Type\n(2) Brand\n Enter a Number: "))
            if option == "1":
                self.changeMyType()
            elif option == "2":
                self.changeMyBrand()
            else:
                print("Enter 1 or 2")
                self.changeScreen()


    def changeMyType(self):
        optionType = input(print("\nThese are your options of phones: \n",self.types,"\nEnter an option [case sensitive]: "))
        self.change_type(optionType)

    def changeMyBrand(self):
        optionBrand = input(print("\nEnter the Brand you would like your phone to be: "))
        self.change_brand(optionBrand)



def main():

    #commands created that fully work:
    #Types of Phones to change to: Touch Screen, Flip, Slider, Bar, Bag
    #get_type()
    #change_type()

    myPhone = Phone()
    myPhone.menu()
main()

Run this python file. When I run it I get None printed after every print. I don't understand why. I know that when your function in python doesn't have a return it will return None, but I don't understand what is going on here. Any other feed back is great too. Right now I have an object Phone that has a menu and other stuff. Tell me if there's another way you would approach this.

回答1:

Everywhere you see input(print("...")), change that to input("..."). My guess is that it was getting caught up in the print() function, and would happily print None.

Be sure to also tag this as python3.x, as this is definitely not a 2.x question.

回答2:

it's because of the:

input(print("(1) See your phone specs \n(2) Change information\n Enter a Number: "))

The print() function returns nothing (i.e. None) that gets printed by input(), you don't need to call the print() function, therefore it should look like:

input("(1) See your phone specs \n(2) Change information\n Enter a Number: ")

来源：https://stackoverflow.com/questions/8628317/python-phone-class-printing-none