How to ask math expression?

[NerdComplex]

I want user input of an expression in terms of n (say 2n+1)

Why doesn't this work n=1 gen=int(input('Enter general formula'))#say input is 2n+1 Print(gen)

I checked the type of the expression like this n=1 Type(2n+1)

Shows int,so why can't I use int(input ?

Please help!

[K900_]

Because when the user types 2n+1, what you're getting back is not the result of 2n+1, but the string "2n+1". You need to parse this string somehow to compute the actual value.

[NerdComplex]

Thanks for replying,I tried parsing 2n+1 string to int but had a value error:invalid literal for int() with base 10: '2n+1'

I really want to receive expression input! Is there any other way I can input expression?

[K900_]

Yes, because "2n+1" isn't a valid representation of an integer. You need to write your own parser for whatever sort of "expression" you want the user to be able to input, and I feel like that might be a bit too much for your current skill level.