Question

import json

file = 'favnum.json'

def save_fav():
    number = input('Type your favourite number: ')
    with open(file, 'w') as f:
        num = json.dump(number, f)
        return num

def get_stored_number():
    try:   
        with open(file) as f:
            number_fav = json.load(f)
        
    except FileNotFoundError:
        return None
    else:
        return number_fav

def main_number():
    num = get_stored_number()
    
    if num:
        print('your favourite number is: ')
        print(num)
    
    else:
        print('the number had not saved before\nthus you have to save it')
        numbers = save_fav()
        print('your number is saved')
        print(numbers)

main_number()

输出：

the number had not saved before
thus you have to save it
Type your favourite number: 3.14
your number is saved
None

Answer 1

您应该在函数save_fav（）中返回数字而不是num

Answer 2

因为json.dump不返回任何值，除了None，并且您将其保存在num中，并且返回num，因此函数也返回num。因此，请返回其他有意义的内容，例如空字符串。

Answer 3

我认为您的职能是

def save_fav():
    number = input('Type your favourite number: ')
    with open(file, 'w') as f:
        num = json.dump(number, f)
        return num

应改为：

def save_fav():
    number = input('Type your favourite number: ')
    with open(file, 'w') as f:
        json.dump(number, f)
    return number

在您的版本中，json.dump返回None，这就是您从函数中返回的内容，然后在以后打印。

为什么在输出中没有输出？蟒蛇

3 个答案: