AttributeError: 'int' 对象没有属性 'isdigit' 和 NameError

Question

I am trying to make a program in which if I enter a positive number then it executes further but if I enter a negative number or a letter it should print 'House price must be a positive number' and it should ask for the input again. This is what I've done so far but when I enter an number I get an AttributeError and when I enter a letter I get a NameError .

import math

while True:
    home_price = input('Enter the price of your dreams house')
    if home_price.isdigit():
        if home_price > 0:    
            home_price = int(house_price)
            break
        else:
            print('House price must be a positive number only')

Answer 1

If you are using Python 2, whose input function does an eval(..) on the user input, and eval("2") returns an int , not a str .

python2 -c 'print(eval("2").__class__)'
<type 'int'>

Your code will work on Python 2 if you replace input with raw_input , which doesnt do an eval .

Answer 2

If you want to keep your loop running until you receive a positive integer, you can just test for negative integers / non digit values entered and then continue to the next iteration. Otherwise you can just break from your loop

while True:
    home_price = input('Enter the price of your dream house: ')

    if not home_price.isdigit() or not int(home_price) > 0:
        print('House price must be a positive integer only')
        continue

    print('The price of your dream house is: %s' % home_price)
    break

Enter the price of your dream house: a
House price must be a positive integer only
Enter the price of your dream house: -1
House price must be a positive integer only
Enter the price of your dream house: 1000
The price of your dream house is: 1000

Answer 3

I recommend exception handling. "-10".isdigit() returns false.

import math

while True:
    home_price = input('Enter the price of your dreams house')
    try:
        if int(home_price) > 0:    
            house_price = int(home_price)
            break
        else:
            print('House price must be a positive number only')
    except ValueError:
        continue

Answer 4

Here is a different method:

home_price_gotten = False

while not home_price_gotten:
    try:
        home_price = input('Enter the price of your dream house\n')
        home_price = int(home_price)
        if home_price < 1:
            raise TypeError
        home_price_gotten = True
        break
    except ValueError:
        print("Home price must be a number, but '{}' is not.".format(home_price))
    except TypeError:
        print('Home price must be a positive number')


print("Success! Home price is : '{}'".format(home_price))

Basically, until the user has given a valid home price, the loop will ask him for one, and try to convert his input to a number. If it fails, it's probably because the input is not a number. If it's smaller than 1, it raises another error. So you're covered.

BTW, this works in python 3 only. For python 2, swap input() for raw_input()