Test user input until conditions are met

Question

In python, I need the input of a user to be between a range of years.

Using if statement returns the error (if he's out of range) to the user and invite him to make another choice of year.

The second time he chooses a year need to be tested again with the same conditions. Which doesn't happen yet.

What would be the best solution to have his input tested all over again, until conditions are met ?

Here's some piece of the actual code

year = input("Enter a year between 1900 and 2099 : ")
if year >= "1900" or year <= "2099":
    year = (input("The year you entered is out of range, please try again : "))
year = int(year)

Thanks in advance

Are you sure you want conditions like year >= "1900"? This will do a string lexicographical comparison, as opposed to comparing if the year is less than 1900. For example, 'a' >= '1900' evaluates to True because a has a larger ASCII value than 1. Also, '19000' >= '1900' or '19000' <= '2099' will also evaluate to True. — Shane Bishop
– Shane Bishop, Commented Jan 20, 2021 at 2:16

wind · Accepted Answer · 2021-01-20 02:19:41Z

1

Explanation:

You can use a while loop. A while loop will run until a certain condition is False. In this case it will run until the break keyword is used, because the condition will always be True. You can also use try and except do make sure the input it an integer. And use continue to start the loop again if it is not an integer.

Code:

prompt = "Enter a year between 1900 and 2099: "

while True:
    year = input(prompt)

    try:
        year = int(year)
    except ValueError:
        prompt = "The year you entered is out of range, please try again : "
        continue 

    if year >= 1900 or year <= 2099:
        break
    else:
        prompt = "The year you entered is out of range, please try again : "

edited Jan 20, 2021 at 2:19

answered Jan 20, 2021 at 2:12

wind

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9 Comments

Zois Tasoulas Over a year ago

should year = int(year) be exactly below the year assignment?

wind Over a year ago

@zois Thanks for pointing it out, I'll fix that.

Zois Tasoulas Over a year ago

Actually you are checking for strings with the if statement, so it works as it is

wind Over a year ago

@zois I'll probably make it integers.

user14998540 Over a year ago

Great, thanks for your input. Strings removed as well. My mistake, or habit.

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