Say I have a function fun(f, x, y)
where x and y are numbers and f is a string specifying a function such as "1 / x ** 2 + y"
.
I wish to use this function f
a lot, say a few million times, and the values of x
and y
change between each use.
Therefore calling eval(f)
takes a significant amount of time as opposed to just calculating the value of the function each time. (About 50x, in my measured case.)
Is there any way to save this function f
so that I would only have to call eval
once?
PS. Please do not discuss the (un)safety of using eval
here, I am aware of it, but this code isn't going anywhere where a 3rd party will run it, nor is it relevant to my question.
literal_eval may be a safer alternative. literal_eval() would only evaluate literals, not algebraic expressions.
Answer: eval is a built-in- function used in python, eval function parses the expression argument and evaluates it as a python expression. In simple words, the eval function evaluates the “String” like a python expression and returns the result as an integer.
You could eval
the lambda
, so you just evaluate it once, and after that it's a function that you can use:
s = "1 / x ** 2 + y"
s = "lambda x,y: "+s
f = eval(s)
x = 2
y = 3
print(f(x,y))
I get 3.25
, but I can change x
and y
as many times I need without evaluating the expression again.
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