Looping through a function in python but redefining a variable when a function from an array of functions gets called

Question

Say I have the following example, in python:

import numpy as np, PROGRAMS as prg
testlist = []
x = 0
n=0
y=[1,2,3,4,5]
x_fn = np.array=([prg.test1(x),prg.test2(x),prg.test3(x)])

for i in range(0,len(x_fn)):
    for j in range(0, len(y)):

        x = y[j]*2
        z=x_fn[i]

        testlist.append(z)
        j = j+1
i = i+1

print testlist

#####PROGRAMS
def test1(x):
    x=x**2

    return x

def test2(x):
    x=x**3

    return x

def test3(x):
    x=x+10

    return x

If x isn't defined before x_fn then an error occurs but if I define it as zero then that is what is used in the calculations. I basically want this code to produce a list with the the defined value of x in the 2nd loop :

x = y[j]*2

for all values of y. I know there would be a way around this mathematically - but I would like to solve it by running the same function and not changing any of the values of y or any of the functions in PROGRAMS.

Basically, is it a good idea to put these functions in a array and run through it element by element or is there a better way to do it?

Thanks in advance for your replies,

Sven D.

wwii · Accepted Answer · 2014-10-24 15:49:16Z

1

Could this be what you want ?

def test1(x):
    x=x**2

    return x

def test2(x):
    x=x**3

    return x

def test3(x):
    x=x+10

    return x


testlist = []
n=0
y_vals=[1,2,3,4,5]

x_fn = [test1, test2, test3]

for fun in x_fn:
    for y in y_vals:

        x = y*2
        z=fun(x)

        testlist.append(z)

print testlist

Functions are objects that can be stored in containers and recalled for use later just like any other object in Python.

edited Oct 24, 2014 at 15:49

wwii

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answered Oct 24, 2014 at 15:40

bruno desthuilliers

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1 Comment

user3614034 Over a year ago

Thank you for your reply -this looks like this exactly what I want - thankyou!

hitzg · Accepted Answer · 2014-10-24 15:41:26Z

0

You don't even need to use numpy arrays. Just use a list (functions) and put the test functions in it. Note, that I have removed the argument. The elements of the functions array are references to the functions, so you can use them in your loop.

import PROGRAMS as prg

testlist = []
y=[1,2,3,4,5]
functions = [prg.test1, prg.test2, prg.test3]

for func in functions:
    for j in y:
        x = j*2
        z = func(x)
        testlist.append(z)

print testlist

#####PROGRAMS
def test1(x):
    x=x**2

    return x

def test2(x):
    x=x**3

    return x

def test3(x):
    x=x+10

    return x

answered Oct 24, 2014 at 15:41

hitzg

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