How do I evaluate Python code from a string quickly?

Question

I'm writing a program that has to execute Python code from a string millions of times. Is there a faster way to do this than using eval() ? Running the code in eval() takes about 100 microseconds, and running it embedded in the program only takes 8 microseconds. Is there a method similar to eval() that takes less time to execute?

Answer 1

I would restructure your code so that it doesn't have to be eval ed (eg, take a function argument instead of a string)

If the equation absolutely must come from a string, you could compile it beforehand:

In [1]: x = y = 0

In [2]: %timeit eval('x ** 2 + y')
5.95 µs ± 223 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)

In [3]: code = compile('x ** 2 + y', '<string>', 'eval')

In [4]: %timeit eval(code)
608 ns ± 9.88 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)

Rather than having eval compile the string to bytecode every time it is called, compile does that beforehand.