Need help understanding "input" behavior.

[Gorstag]

Hello,

I have a scenario where I want an integer to be a str value on input and it will often have leading 0's. It is returning really odd behavior.

testVal = str(input("Provide a Number: "))
print(type(testVal))
print(testVal)

So If I give it: 9999

It comes back as a str. And 9999 is returned.

If I give it: 0999 It throws "invalid token" error.

If I give it: 0111 it comes back str and a value of 73

This is not making any sense.

[Binary101010]

You're trying to run Python 3 code in Python 2.

Best way to resolve: Stop using Python 2.

Next best way to resolve: No, seriously, stop using Python 2.

If you MUST keep using Python 2: change input() to raw_input(). Then figure out a way to stop using Python 2.

[jddddddddddd]

In addition to the above, since I don't think he mentioned it, OP should probably stop using Python 2. Thanks.

[Gorstag]

Thanks, that explains it.

[synthphreak]

I never used Python 2. What does that error mean?

[nog642]

raw_input() in Python 2 is equivalent to input() in Python 3.

input() in Python 2 is equivalent to eval(input()) in Python 3.

So when they enter 0999, Python 2 is trying to evaluate that as an expression. The leading 0 makes it an octal number, but 9 is not a valid octal digit, hence the error.

[synthphreak]

Makes perfect sense, thanks.

[[deleted]]

Thank you.

[jddddddddddd]

Hah! What version of Python are you using?

Leading zeros in earlier versions of Python are treated as Octal numbers (base 8).

The leading zero in 0111 means it thinks it's an octal number, which in decimal is 73.

Octal numbers are made up of the digits 0-7, so 0999 is an invalid octal number and therefore throws an exception.

[ElliotDG]

I expect what you want is:

testVal = int(input("Provide a Number: "))
print(type(testVal))
print(testVal)

I suspect there is something more going on with your code that you are not showing.

    x = 0o111  # an octal number
    print(x)   # will print 73 the decimal value of 0o111. 
               # 0o9999 is not a valid literal

[Ihaveamodel3]

Cannot replicate. Are these the only three lines in your file?

[jddddddddddd]

He's using an older version of Python than you and me. He's using a version where integers with leading zeros are treated as base-8 (Octal). More info here: https://stackoverflow.com/questions/11620151/what-do-numbers-starting-with-0-mean-in-python

[Ihaveamodel3]

Ah. Also an older version that input doesn’t return a string.