How can i optimize this code? Maybe though a list comporehension?-CodePudding

I need to accelerate this code:

The first which i think i can do is to modify the way to obtain a list, thats the part i write in BOLD.

¿Some ideas? I try to do it with List comprehension but always give me the error of referenced before assignment.

def transform(A, x):
    
    from math import factorial
    
    def comb(i,x):
        return factorial(i)/(factorial(x)*factorial(i-x))

    lis = []

    # --- FROM HERE ---
    for i in A:
        suma = 0
        for j in range(x,i 1):
            suma  = comb(j,x)
        lis.append(suma)
    # --- TO HERE ---

    return lis
    
    res = lis[0]  
    
    for i in lis[1:]:
        res = int(res) ^ int(i)
                                        
    return res

Thanks

CodePudding user response：

I'm going to actually answer your specific question, though as mentioned by everyone above, it will almost certainly not improve your running speed. You have:

    suma = 0
    for j in range(x,i 1):
       suma  = comb(j,x)

This can be turned into a single sum:

    suma = sum(comb(j, x) for j in range(x, i   1))

Your outer loop is:

lis = []
for i in A:
    suma = sum(....) # See code above
    lis.append(suma)

which can be turned into the following list comprehension:

lis = [sum(....) for i in A]