How do I find out if a power will take too long to compute? (Python)

I wrote a python program that generates random mathematical strings, such as "2+3**4/3" and "3**3**50-2", and then uses eval() to compute them.

Computing "2+3**4/3" will work fine but evaluating "3**3**50-2" will take too long since it will be a very large number. I need to check if the power will be too large to compute before it tries, or I need to terminate the function after a certain amount of time.

Since this function needs to be run tens of thousands of times, efficiency is very important

I’ve tried using the "multiprocessing" and "threading" libraries to terminate the thread if it takes over a second, but these solutions slow down the program too much.

Any suggestions? I’m completely stumped on this one. Thanks.

try:
    eval("math.pow(a,b)")
except:
    print("too long to compute")