Xtykutl

A = [18.0,10.0]; B = [13.0,15.0]; C = [10.5,12.0];

these are the variables and think about function like

def hlf(A,B,C):

       return A**(-1.0/2.0)-0.2*B-43+C

print "T:"

hlf(A,B,C)

Firstly, I want to use first values of the A B and C in the equation. After I want to use second values. How can I do this ?

map + list

Note map can take multiple iterable arguments:

res = map(hlf, A, B, C)



[-34.86429773960448, -33.68377223398316]

In Python 2.7, map returns a list. In Python 3.x map returns an iterator, so you can either iterate lazily or exhaust via list, i.e. list(map(hfl, A, B, C)).

Reference:

map(function, iterable, ...)

...If additional iterable arguments are passed, function must
take that many arguments and is applied to the items from all
iterables in parallel.

zip + list comprehension

You can use zip within a list comprehension. For clarity, you should avoid naming your arguments the same as your variables.

A = [18.0,10.0]; B = [13.0,15.0]; C = [10.5,12.0]; 



def hlf(x, y, z):

    return x**(-1.0/2.0) - 0.2*y - 43 + z



res = [hlf(*vars) for vars in zip(A, B, C)]



[-34.86429773960448, -33.68377223398316]

Vectorize with Numpy. Best Performace

Normally its much better try to vectorize this kind of operations with numpy, because the best performance results. When you vectorize instead to use a loop, you are using all your cores, and its the fastest solution. You should vectorize the operation with numpy. Something like this:

import numpy as np



A = [18.0,10.0]; B = [13.0,15.0]; C = [10.5,12.0];

a = np.array(A)

b = np.array(B)

c = np.array(C)

And now your function with the new vectors like arguments:

def hlf(a_vector,b_vector,c_vector):

    return a_vector**(-1.0/2.0)-0.2*b_vector-43+c_vector

And finally call your new function vectorized:

print (hlf(a_vector = a,b_vector = b,c_vector = c))

Output:

>>> array([-34.86429774, -33.68377223])

If you want to keep your function as is, you should call it N times with:

for i in range(N):

    result = hlf(A[i], B[i], C[i])

    print(result)

Another interesting method is to make a generator with your function:

A = [18.0,10.0]

B = [13.0,15.0]

C = [10.5,12.0];



def hlf(*args):

    i=0

    while i < len(args[0]):

        yield args[0][i]**(-1.0/2.0) - 0.2*args[1][i] - 43 + args[2][i]

        i += 1



results = hlf(A, B, C)

for r in results:

    print(r)

Output:

-34.86429773960448

-33.68377223398316

Last one is rather edicational if you want to practice python generators.