How to import class with all functions in Python from different file?

Question

I created 'class V' in file 'V.py' with some functions, which I want to keep using in other projects, but when I call any of these functions I get an error that the name is not defined. I tried all solutions that I could find and nothing fixes it. Hope somebody knows what am I doing wrong..

class V(object):

    def magnitude(self):
        a=0
        for i in range(len(self)):
            for j in range(len(self[i])):
                a= a + self[i][j] **2
        return sqrt(a)

Calling a function:

from V import V
A = np.array([[1,2,3],[4,0,6],[7,8,9]])
print magnitude(A)

Error:

NameError: name 'magnitude' is not defined

What about https://stackoverflow.com/questions/6757192/importing-a-function-from-a-class-in-another-file? — sander, May 07 '20 at 10:59
It should be `from V.V import magnitude`. Then your call to magnitude will work — user3479780, May 07 '20 at 11:00
You can check this : https://stackoverflow.com/questions/20309456/call-a-function-from-another-file-in-python — Priyanka Jain, May 07 '20 at 11:02

score 0 · Accepted Answer · answered May 07 '20 at 11:30

0

Refactor your class method to take a parameter, and create an object of class before accessing the method.

from math import sqrt


class V(object):

    def magnitude(self, A):
        a = 0
        for i in range(len(A)):
            for j in range(len(A[i])):
                a = a + A[i][j] ** 2
        return sqrt(a)

import numpy as np
from V import V

v = V()
A = np.array([[1,2,3],[4,0,6],[7,8,9]])
print (v.magnitude(A))

This will work. The reason is you are trying to access class method without creating a class object and passing a parameter inside the method too. self is basically the object on which the method is being called.

answered May 07 '20 at 11:30

sandeshdaundkar

883
1
7
14

Thank you for the response! I ran the code and its giving me some wierd error "TypeError: magnitude() takes exactly 1 argument (2 given)". However if I run it within the original file it works without errors. – Petr Frolkin May 08 '20 at 02:05
Did you change your class ? I have tested this code shouldn't break – sandeshdaundkar May 08 '20 at 02:39

score -2 · Answer 2 · answered May 07 '20 at 11:05

-2

You should pass magnitude to class, not to method try:

from V import V
A = np.array([[1,2,3],[4,0,6],[7,8,9]])
m = V(A)
print (V)

answered May 07 '20 at 11:05

djangodjames

199
1
11

How to import class with all functions in Python from different file?

2 Answers2