[Tutor] Beginner - understanding randint arguments

[Alan Gauld]

On 15/02/14 16:25, Marc Eymard wrote:

> Here is what happens in my script:
>
>      >>> import random
>      >>> low_range = -1
>      >>> high_range = 101
>      >>> random.randint(low_range + 1, high_range - 1)
>     56
>      >>> low_range
>     -1
>      >>> high_range
>     101*
>
> I was rather expecting:
>
>       >>> low_range
>     0
>      >>> high_range
>     100

Really? Why?
You never change low_range or high_range so why would
their values change?

The help() for randint says:

randint(self, a, b) method of random.Random instance
     Return random integer in range [a, b], including both end points.

So the function doesn't change the values either it
just returns a random number between them.

> Can somebody explain why both low_range and high_range are still
> returning their initial values ?

Because you didn't change them.
When you called randint you passed in two expressions:

low_range+1 and high_range-1
which Python evaluated as 0 and 100.

But that did not change your variable values in any way, it just created 
new values that were passed into randint() as 'a' and 'b' respectively.

-- 
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
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