Python：通过在 function 之外操作变量来验证用户输入

Question

I am somewhat new to python and have a very basic understanding.

I am creating a very simple program that works as a decision map. The user types 0 for no, and 1 for yes, in order to continue down the decision map and ultimately reach a conclusion. For each decision, the answer (0 or 1) is saved in a new variable.

MY PROBLEM: I created a function to validate that the user is entering a valid response. I want to use this function after every-time I ask for a new response for each new decision/ variable. For example, in the first variable, seq , if the user enters 2, it should enter the validation function and enter a loop until the user enters 0 or 1. However, once they enter 0 or 1, I don't know how to re-assign that new value to seq in order to continue with the decision map.

What I have tried: Setting x to global, initiate x = 0 , set the variable (ie seq ) to global, and add seq = valid_user_input(x)

Any help would be greatly appreciated. I am looking for a simple solution that is hopefully not too advanced for me. HERE IS A LINK TO EDIT MY CODE! Repl.it map program

#Validation Function
def valid_user_input(x):

  while x != 1 and x != 0:
    x = int(input("Please answer the following question with [0 being no] and [1 being yes]\n"))
    print("x value is: ", x)
  return x

#Conditions/ Call Validation Function
seq = int(input("Is your equation in the {An} form or a list of terms?\n0. No]\n[1. Yes]\n"))
valid_user_input(seq) #CALL FUNCTION

if seq == 0: #seq no
  print("You have a series!\n")

  part = int(input("Is your equation in the form Sn?\n[1. Yes]\n[0. No]\n"))
  valid_user_input(part) #CALL FUNCTION

    if part == 0: #part no

    #Continue conditions...

    if part == 1: #part yes

if seq == 1: #seq yes
  print("You have a sequence!")

  tels = int(input("Do all terms cancel out except first and last term?\n[1. Yes]\n[0. No]\n"))
  valid_user_input(tels) #CALL FUNCTION

Answer 1

You design your function so it has one task: return 0 or 1 to a given text (your question):

def ask_01(text):
    """Asks text's content until either 0 or 1 are answered and returns that."""
    r = -1
    retry = False
    while r not in {0,1}:
        try:
            if retry:
                print("Wrong input")
            retry = True
            r = int(input(text + " Yes (1) or No (0)?"))
        except ValueError:  # if non-intergers are answered it gets cought here
            pass
    return r

weather_ok = ask_01("Ok Weather?")
happy = ask_01("Are you happy?")
print(weather_ok, happy)

and only ever leave the function if the input is valid:

Outputs for inputs: 4,a,1,3,i,0

Ok Weather? Yes (1) or No (0)? 4
Wrong input
Ok Weather? Yes (1) or No (0)? a
Wrong input
Ok Weather? Yes (1) or No (0)? 1
Are you happy? Yes (1) or No (0)? 3
Wrong input
Are you happy? Yes (1) or No (0)? i
Wrong input
Are you happy? Yes (1) or No (0)? 0

1 0

More on validation:

• Asking the user for input until they give a valid response

Answer 2

Here's a contrived example. I'm not even suggesting that this is a good way of doing what you're trying to achieve (deleting the prompt key-value pair feels lame) - All I'm trying to show here is that a data-driven approach might be desirable since it helps to cut down on if-statements.

tree = {

    "prompt": "Do you have a cat (0) or a dog (1)?",

    "0": {
        "prompt": "Is your cat male (0) or female (1)?",
        "0": {"prompt": "You have a male cat!"},
        "1": {"prompt": "You have a female cat!"}
        },
    "1": {
        "prompt": "Is your dog male (0) or female (1)?",
        "0": {"prompt": "You have a male dog!"},
        "1": {"prompt": "You have a female dog!"}
        }

}

current_branch = tree
while True:
    print(current_branch["prompt"])
    del current_branch["prompt"]
    if not current_branch:
        break
    for key in current_branch:
        print(f">[{key}]")
    while True:
        user_input = input("Enter your selection: ")
        if user_input in current_branch:
            break
    current_branch = current_branch[user_input]

Example Output:

Do you have a cat (0) or a dog (1)?
>[0]
>[1]
Enter your selection: asdf
Enter your selection: 3
Enter your selection: 2
Enter your selection: 1
Is your dog male (0) or female (1)?
>[0]
>[1]
Enter your selection: abcd
Enter your selection: a
Enter your selection: 0a
Enter your selection: 0
You have a male dog!
>>> 

Answer 3

I would recommend you making a question asking class, where you can handle the behaviour for every question, and have your flow simplified:

from dataclasses import dataclass


@dataclass
class Question:
    question: str
    answer: int = None

    def _validate(self, answer):
        if answer not in (0, 1):
            print("Please answer the following question with [0 being no] and [1 being yes]\n")
            raise ValueError

    def ask(self) -> int:
        self.answer = input(self.question)
        try:
            self.answer = int(self.answer)
            self._validate(self.answer)
        except ValueError:
            return self.ask()
        return self.answer


q1 = Question('Are you blue?')
q2 = Question('Do you like oceans?')
q3 = Question('Are you virtual?')

if q1.ask():
    if q2.ask():
        print('You are a dolphin')
    else:
        print('I don\'t know what you are')
else:
    if q3.ask():
        print('Get connected')
    else:
        print('I can\' help you')

# Also can access previous answers:
# q1.answer -> 0 or 1