CODEWITHSUNDEEP
python
Gavin
Gavin

Reputation: 141

Why does this input to int does not work properly?

I'm trying to solve this in Python and not sure why it isn't working...

x = int(input("Enter the value of X: "))
y = int(input("Enter the value of Y: "))
print(y)
input("...")

The problem is Y. I input exactly as follows without quotes: "2 * x" I have tried a lot of things and researched a lot (as I do before asking) but I am stumped here. Perhaps it's because I'm such a basic user.

Upvotes: 0

Views: 2337

Answers (3)

zhangxaochen
zhangxaochen

Reputation: 34017

seems you are reading books with python2, but you have installed python3. In python2, input equals to eval(raw_input(prompt)), that's why when you input 2 * x, it evaluates the value of the expression and assign it to y.

In python3, input just get user input as strings, not to eval that as an expression, you may need explicitly eval, which is a bad practice and dangerous:

In [7]: x=2

In [8]: y=eval(input('input Y:'))

input Y:3*x


In [9]: y
Out[9]: 6

All in all, use: raw_input in py2, input in py3, never use eval (or input in py2) in your production code.

Upvotes: 4

rae1
rae1

Reputation: 6144

You cannot pass expression as string literals to int this way. You can do this instead,

x = int(input("Enter the value of X: "))
y = x * 2
print(y)
input("...")

If you instead, require another value to be used in the multiplication, you can do,

x = int(input("Enter the value of X: "))
y = int(input("Enter the value of Y: "))
z = x * y
print(z)
input("...")

Upvotes: 0

inspectorG4dget
inspectorG4dget

Reputation: 113915

This is because 2 * x is not an integer. It is, when you evaluate it, though; but that's not what input does.

So what you want is this:

x = int(input("Enter the value of X: "))
y = int(input("Enter the value of Y: ")) * x

Then, input 2, when asked for Y

Upvotes: 0

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