How can I get rid of using exec when getting variables from a yaml file

Question

I am reading a configuration file that contains some queries like these:

query = 'column_a in @certain_variable'

and variables:

variables:
  certain_variable = ["val1","val2"]
  certain_variable2 = ["val1","val2"]
  ... more

And the way I am doing it now is:

for k, v in variables.items():
    exec (k + '=v')

df.query(query)

Because I don't see another way of making available variables from the yaml file to pandas.

The reason I am trying to remove exec is because I have some subfunctions that leads to errors (as described here: Why doesn't exec work in a function with a subfunction?)