Python: Way to speed up a repeatedly executed eval statement?

Question

In my code, I\'m using eval to evaluate a string expression given by the user. Is there a way to compile or otherwise speed up this statement?

Answer 1

You can avoid the overhead by compiling the expression in advance using compiler.compile() for Python 2 or compile() for Python 3 :

In [1]: import math, compiler

In [2]: v = {'x': 2, 'y': 4}

In [3]: expression = "math.sin(v['x']) * v['y']"

In [4]: %timeit eval(expression)
10000 loops, best of 3: 19.5 us per loop

In [5]: compiled = compiler.compile(expression, '', 'eval')

In [6]: %timeit eval(compiled)
1000000 loops, best of 3: 823 ns per loop

Just make sure you do the compiling only once (outside of the loop). As mentioned in comments, when using eval on user submitted strings make sure you are very careful about what you accept.