[Tutor] Invalid Token Problem

[Alan Gauld]

On 20/07/12 02:01, Ross Wilson wrote:

> More specifically, eval() is dangerous if you try to evaluate a string
> supplied by someone else.  You really can't predict what will happen.

It really doesn't matter who provides the string, Python and eval() 
don't care. They will behave just as dangerously if you provide the 
wrong string.

And that's the problem because even if you think the string you are 
feeding eval() is safe it only needs a small typo to occasionally
turn it into something not safe - and just once is enough to be painful.

So while eval() introduces security issues where other people try to 
maliciously damage your code, eval() is dangerous even in "normal" use
because it has the potential to do damage.

Think of eval() as being like an old fashioned scythe for cutting hay. A 
scythe is dangerous, used wrongly it can cut off your foot. Used 
correctly it won't. But no matter how long you have been using a
scythe it remains dangerous and you forget that at your peril!

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