Exec statement python

Question

How do I execute a statement dynamically in Python?

For ex: assume the value x contains the following expression, (a+b)/2,

a = 1
b = 3
x = (a+b)/2

The value for x will be from a table

score 2 · Accepted Answer · edited May 23 '17 at 12:12

2

Probably you want eval

#!/usr/bin/env python

a = 1
b = 3
x = "(a+b)/2"
print eval(x)

But it's usually considered a bad practice (click here for a more elaborate and funnier explanation)

edited May 23 '17 at 12:12

Community

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answered Aug 21 '12 at 17:37

Savir

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score 0 · Answer 2 · answered Aug 21 '12 at 17:34

0

You can do:

a = 1
b = 3
x = '(a+b)/2'

print eval(x)

Note that the value for x is enclosed in quotes as eval requires a string or code object.

Also, perhaps read this to make sure you use it safely (as that can often be a concern and I'm not going to pretend to be an expert in its flaws :) ).

answered Aug 21 '12 at 17:34

RocketDonkey

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There is no way to use eval safely, that article is wrong. Read [Eval Really is Dangerous](http://nedbatchelder.com/blog/201206/eval_really_is_dangerous.html) for details. – Ned Batchelder Aug 21 '12 at 21:31
Haha, yeah, I have actually completely avoided it solely due to reading others' comments on this site (and will continue to do so :) ). – RocketDonkey Aug 21 '12 at 21:37

score 0 · Answer 3 · answered Aug 21 '12 at 17:35

0

Although python has both "exec()" and "eval()", I believe you wan to use the latter in this case:

>>> a = 1
>>> b = 3
>>> x = "(a + b)/2"
>>> eval(x)
2

answered Aug 21 '12 at 17:35

D.C.

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score 0 · Answer 4 · answered Aug 21 '12 at 17:37

0

You can use eval, as in

eval(x)

Actually you can use

x=eval('(a+b)/2')

to get the result (eval will return the result of the computation in this case).

answered Aug 21 '12 at 17:37

hochl

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Exec statement python

4 Answers4