How to make an object generator

Question

I'm trying to make a map for a dnd bot. My plan is to make a xy grid of objects that I can store data for each space in, and then later map it out (already figured out in another code). I've been butting my head in with this and can't quite get things worked out, as the code will either print out an error, or a None.
https://code.sololearn.com/c0QqNFToX0tj/?ref=app
How would I get something like this to work.

Answer 1

You want to calculate a value from strings. For that you need eval, not exec

Answer 2

Yep, switching the exec to eval on print did it. I wasn't familiar with eval prior to this and just thought of exec as a str or int for "raw text" (the text that's needed for naming variable and actual code)
Thanks

Answer 3

exec executes code, for example some print statement. eval calculates an expression.

So basically, when you want to have a value, take eval.

(And if you can prevent it, best use neither - it's not the safest tool in the box.)

Answer 4

Understood. But how exactly is it unsafe, besides having an open input into the exec/eval or potential errors if you do it wrong. Cause I'll probably have to use it fairly often to turn strings into variable names and similar

Answer 5

Let me update weapon forge code, so I can show you

Answer 6

Why do you have to have a variable name for a created weapon? Why this line with exec?

Why don't you just, for example, create a dictionary

d = {}

and go like:

d['Whatever'] = weapon(bla, bla... )

Answer 7

Then you can just do

show(d[thatname])

Answer 8

Ok, I get what you're saying. But I'm not going to update the weapon forge, since that's just an example. It just slipped my mind that dictionaries could use strings as keys, and I was in the middle of typing the long comment when you sent that, so I didn't see your dictionary suggestion before I posted it. So, is there any risk to the eval and exec in the "working with classes" code (the original question)(ie, using exec and eval separate from any input)? If not, I think that's it, and thanks for all the help

Answer 9

Usually there are simple ways to convert strings to values without using eval or exec.

Do you have a situation in mind where you would think you have to use eval?

Answer 10

I think my main one is conversion for variable names, either in the creation or calling of a var. I'm not exactly sure what else I'll need as I'm learning as I'm going (I got my basics covered though). I just know that turning input into that "raw text" will definitely come in handy. I'll write some example code for the situation I explained

Answer 11

https://code.sololearn.com/cUT1zKW20oHX/?ref=app

Here, I need exec and eval to turn strings into "raw text" to make and call variable names

Answer 12

HonFu I would also need exec and eval if I were to write more code, to make it where people can make weapons based on input

Answer 13

You should usually try your best to do without eval and exec. It's generally possible and usually not hard to find a way.

Answer 14

So what are suitable replacements for eval and exec?

Answer 15

That depends on what exactly you want to do.

exec and eval should only be used in very controlled situations.

Simply spoken, your user could write 'delete hard-drive's content'. What if you exec that?

Answer 16

For calling variable names, I can write an if statements making sure the input matches one of the variable names, else output invalid var name.
However I'm not exactly sure what to do when creating variable names and such with input

Answer 17

Why do you need to do that?

Answer 18

Done, though you'll need to run it elsewhere because sololearn makes an eof error if you do more than one input

Answer 19

I believe the code is safe enough, except the name, I'm not sure what to do there

Answer 20

https://www.sololearn.com/post/214561/?ref=app
Here's the output I got from it