Use Eval With Dictionary Without Losing Imported Modules In Python2

I have a string to be executed inside my python program and I want to change some variables in the string like x[1], x[2] to something else. I had previously used eval with 2 argum

Solution 1:

Build your globals dict with globals() as a base:

from math import log

# Copy the globals() dict so changes don't affect real globals
eval_globals = globals().copy()
# Tweak the copy to add desired new global
eval_globals[x[1]] = 1# eval using the updated copyeval('log(x[1])', eval_globals)

Alternatively, you can use three-arg eval to use globals() unmodified, but also supply a locals dict that will be checked (and modified) first, in preference to global values:

eval('log(x[1])', globals(), {x[1]: 1})

In theory, the latter approach could allow the expression to mutate the original globals, so adding .copy() to make it eval('log(x[1])', globals().copy(), {x[1]: 1}) minimizes the risk of that happening accidentally. But pathological/malicious code could work around that; eval is dangerous after all, don't trust it for arbitrary inputs no matter how sandboxed you make it.