Pass Python function from outside to another function

Question

I have a function, which calculate features from my data. Here is a dummy sample of it

import numpy as np
val1=[1,2,3,4,5,6,7,8,9]
val2=[2,4,6,8,10,12,14,16]
data=[]
def feature_cal(val):
    val=np.array(val)
    value=val*2
    data.append(np.mean(value))
feature_cal(val1)
feature_cal(val2)

What i want is to define the function np.mean() out of my function feature_cal.
Pseudo code

def feature_cal(val,method):
    val=np.array(val)
    value=val*2
    data.append(method(value))
feature_cal(val1,method=np.mean())
feature_cal(val2,method=np.mean())

This will help me to calculate other features such as np.std(), np.var() without changing the original function

Remove paranthesis: feature_cal(val1,method=np.mean).

Austin
– Austin

2019-04-28 07:47:58 +00:00
Commented Apr 28, 2019 at 7:47 — Austin
– Austin, Commented Apr 28, 2019 at 7:47

Cloudomation · Accepted Answer · 2019-04-28 08:33:13Z

4

To pass the function you need to remove the parentheses after np.mean:

import numpy as np

def feature_cal(val, method):
    val = np.array(val)
    value = val*2
    data.append(method(value))

feature_cal(val1, method=np.mean)
feature_cal(val2, method=np.mean)

EDIT

If you need to pass arguments to np.mean you can use functools.partial:

import numpy as np
import functools

def feature_cal(val, method):
    val = np.array(val)
    value = val*2
    data.append(method(value))

bound_function = functools.partial(np.mean, axis=1)
feature_cal(val1, method=bound_function)
feature_cal(val2, method=bound_function)

edited Apr 28, 2019 at 8:33

answered Apr 28, 2019 at 7:47

Cloudomation

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1 Comment

Talha Anwar Over a year ago

if i have to pass some parameters to np.mean() such as axis=0 or axis=1. How can i pass it this way when i am not using parentheses.

Marcin Orlowski · Accepted Answer · 2019-04-28 07:46:49Z

0

If I got you correctly you need to pass callable and not result of function invocation as you do now. So this line

feature_cal(val1,method=np.mean())

Shouls read

feature_cal(val1,method=np.mean)

answered Apr 28, 2019 at 7:46

Marcin Orlowski

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Comments

Bar Gans · Accepted Answer · 2019-04-28 07:56:01Z

0

You can simply insert a method as a parameter into a function by entering the name of the method (without parentheses) and by reading the function you will call(with parentheses) the inserted parameter

    def feature_cal(val,method):
        val=np.array(val)
        value=val*2
        data.append(method(value))



   feature_cal(val1,method=np.mean)

answered Apr 28, 2019 at 7:56

Bar Gans

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