Getting a user inputted equation

Question

I'm currently trying to let a user input their own equation for my calculator. If I run it with just my own equation, it works perfectly, however I can't get it to work from a user input. Any advice? Thanks This part of the code works

 def function(x):
     equation = 3*exp(x)
     return equation

When I change to a user input, It doesn't

 def function(x):
     equation = input('Insert your equation)
    return equation

I don't get why this question got downvoted. Many programmers who're learning Python often want to do this kind of a task. — i spin and then i lock, Feb 22 '21 at 16:15
Does this answer your question? [Evaluating a mathematical expression in a string](https://stackoverflow.com/questions/2371436/evaluating-a-mathematical-expression-in-a-string) — Peter O., Feb 22 '21 at 17:09

i spin and then i lock · Answer 1 · 2021-02-22T16:11:23.030

3

You can use the eval() function. For example:

from math import exp


def function(x):
     equation = eval(user_input)
     return equation


user_input = "3*exp(x)"
x = 2
print(function(x))

But, citing realpython, "eval() is considered insecure because it allows you (or your users) to dynamically execute arbitrary Python code. This is considered bad programming practice because the code that you're reading (or writing) is not the code that you'll execute."

edited Feb 22 '21 at 16:11

answered Feb 22 '21 at 16:05

i spin and then i lock

415
2
17

1

https://stackoverflow.com/questions/1832940/why-is-using-eval-a-bad-practice – Pranav Hosangadi Feb 22 '21 at 16:06
There we go! It's important to include the caveats when suggesting a bad practice in an answer – Pranav Hosangadi Feb 22 '21 at 16:07
I added that, in general, eval is considered a bad practice. But in this particular case, it suits the OP's needs. I was going to do it in the edit. :) – i spin and then i lock Feb 22 '21 at 16:08
I noticed you added it. That's why I changed my downvote to an upvote. – Pranav Hosangadi Feb 22 '21 at 16:09
Thank you! Massive help @kenticent – SJ Rowell Feb 22 '21 at 16:43

Getting a user inputted equation

1 Answers1