Question

I need to construct an if statement from the data coming from the client as below:

conditions: condition1, condition2, condition3, condition4
logical operators: lo1, lo2, lo3 (Possible values: “and” “or”)

Eg.

if condition1 lo1 condition2 lo3 condition4:
    # Do something

I can think of eval/exec but not sure how safe they are! Any better approach or alternative?
Appreciate your responses 🙂

PS: Client-side: Flex, Server-side: Python, over internet

Thanks

Answer 1

Define your own function that takes two conditions and an operator and evaluates:

def my_eval(condition1, lo, condition2)
    return {
      'and': condition1 and condition2,
      'or': condition1 or condition2
           }[lo]

and then evaluate the lot:

condition = conditions[0]
for cond, op in zip(conditions[1:], operators):
    condition = my_eval(condition, op, cond)

Feel free to preprocess condition1 and condition2 in my_eval, you probably don’t intend to truth test the strings 🙂