import module within python lambda function

Question

Is it possible to import module within a python lambda function? For example, i have a lambda function which requires to import math

import math
is_na_yes_no = lambda x: 'Yes' if math.isnan(x) else 'No'

How can I include the import math statement within the lambda function?

To clarify, I have a scenario that need to put some lambda functions in a config file and evaluate the function in some other python files, exmample:

{
  "is_na_yes_no" = "lambda x: 'Yes' if math.isnan(x) else 'No'"
}

In this case, the python file that evaluating those lambda functions need to all modules required.

[What is the XY Problem?](https://meta.stackexchange.com/questions/66377/what-is-the-xy-problem) — Sayse, Oct 04 '19 at 09:32
so for each iterable you want to import again and again, this is bad — sahasrara62, Oct 04 '19 at 09:32
@aran-fey i want to add flexibility to my code by putting some lambda functions in a config file, but issue is that the python file executing those lambda functions must know what modules to import — henrywongkk, Oct 04 '19 at 09:33
@Sayse it is not a XY problem, but i have a scenario it does not work — henrywongkk, Oct 04 '19 at 09:34
@prashantrana - No iterables involved here. OP, You don't need a lambda here at all, just define the function and import that to other modules that would use it. — Sayse, Oct 04 '19 at 09:34
You may be able to use importlib [as seen here](https://stackoverflow.com/questions/8718885/import-module-from-string-variable/8719100) to create a lambda to import from a string, but id say its highly inadvisable to do so — Kevin Müller, Oct 04 '19 at 09:36
Yay codegolfing.. `lambda x:'Yes'if __import__('math').isnan(x)else'No'` — L3viathan, Oct 04 '19 at 09:47
Why do they have to be lambda functions? Why can't they be real functions? — Aran-Fey, Oct 04 '19 at 09:50
@Aran-Fey because my code is storing the functions as string in a json file, which is user-configurable. please let me know if you have other suggestions — henrywongkk, Oct 04 '19 at 09:56
You can call an extra function in your lambda which imports a module. — mortymacs, Oct 04 '19 at 10:08

score 2 · Accepted Answer · answered Oct 04 '19 at 10:07

Thanks @L3viathan for the answer.

Here is same thing without having to import math in the module.

is_na_yes_no = lambda x: 'Yes' if __import__('math').isnan(x) else 'No'

It highlights the flexibility of python -- __import__ feature can be used in lambda functions instead of having them written out before hand.

import module within python lambda function

1 Answers1