Calculate lists in Python 3.7

Question

I was wondering if it was possible to calculate a list, for example this one

calculation = [1, "+", 2, "*", 15]

so it returns 31.

Where does that list come from? Is it user input? Or is it generated by your own code? — Aran-Fey, Sep 22 '18 at 11:43

Vishvajit Pathak · Accepted Answer · 2018-09-23T18:38:07.070

2

Don't use eval ever. Check this post

Instead you can refer some other library like asteval

from asteval import Interpreter
aeval = Interpreter()
calculation = [1, "+", 2, "*", 15]
aeval.eval(''.join(map(str, calculation)))

edited Sep 23 '18 at 18:38

answered Sep 22 '18 at 13:57

Vishvajit Pathak

Worked great for me, was wondering if there was a alternative to eval. Thanks a bunch! – Luca Roth Sep 23 '18 at 12:14

score 0 · Answer 2 · answered Sep 22 '18 at 11:40

0

Maybe you could take a look at a binary expression tree.

answered Sep 22 '18 at 11:40

Rick de Gier

score 0 · Answer 3 · answered Sep 22 '18 at 11:41

Sure:

eval(' '.join(map(str, calculation)), {}, {})

The inner join (no pun intended) builds a single string which is valid Python code, then you simply eval() it.

The two {}s are optional, they make it so the code runs without access to the surrounding global and local variables.

score 0 · Answer 4 · answered Sep 22 '18 at 11:52

0

eval can be used for evaluating an expression (which is in the form of a string) in python.

Desired output can be obtained as below

eval(''.join([str(x) for x in calculation]))

answered Sep 22 '18 at 11:52

Jagadeesh Dondeti

4 Answers4