[Python] Looping through object instance variables does not change value

I have a class that contains two object instance variables.

import numpy as np
class test(object):
def __init__(self):
self.a=np.array((1,2))
self.b=np.array((1,2))


I need a method that does similar operations to each variable. I thought that I could loop over the variable and it would change the values in place. However, when i execute the numpy insert and assign the value to a, it does not change self.a.

def indirect_method(self):
arrs = [self.a, self.b]
for a in arrs:
a = np.insert(l,1,3)
t=test()

t.indirect_method()

t.a
Out[82]: array([1, 2])

t.b
Out[83]: array([1, 2])


If I print the ID of self.a and a, initially they are the same, but after the insert operation the ID of a changes.

def indirect_method(self):
arrs = [self.a,]
print(id(self.a))
for a in arrs:
print(id(a))
a = np.insert(l,1,3)
print(id(a))


t=test()

t.indirect_method()

4756930896
4756930896
4744668432


If I modify the object variables directly it works fine.

def direct_method(self):
self.a = np.insert(self.a,1,3)
self.b = np.insert(self.b,1,3)

t=test()

t.direct_method()

t.a
Out[77]: array([1, 3, 2])

t.b
Out[78]: array([1, 3, 2])


How can I update self.a and self.b through an intermediary variable? This would save a lot of duplicated code since the only part of my method that needs to change is the location where the data is inserted.

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