How do functions and lists work together?

Question

when I am trying to append a list, it's working weirdly. Suppose this is my code:

a = [1]
b = a
c = a

def func(a):
    a.append([50])

Here is the output:

a
[1]    
b
[1]
c
[1]

func(c)
c
[1,50]  # good till now

But now when I try to print a or b, I should get just [1] right? But no, here's what I get:

b
[1,50]

Please explain...

Namit Singal · Accepted Answer · 2015-06-04T22:54:32.910

0

Here 'b' and 'c' have reference of 'a'. Since 'a' is a list and is mutable, any changes to 'a' will also reflect in 'b' and 'c'.

to make a copy of object, use

import copy
a=[10]
b= copy.deepcopy(a)
c= copy.deepcopy(a)

Now pass 'a', 'b' or 'c' to the function, you will get separate values for each of them

Cheers

edited Jun 04 '15 at 22:54

answered Jun 04 '15 at 22:48

Namit Singal

Then how should i declare b such that it gets initialised to a but not change whenever c is changed? – honey Jun 04 '15 at 22:49
Check the linked duplicate questions. – TigerhawkT3 Jun 04 '15 at 22:50
use `b = a[:]` or `b = copy.deepcopy(a)` – ZdaR Jun 04 '15 at 22:50
@Namit Singal: Thank you – honey Jun 04 '15 at 22:53
@honey you are welcome :) – Namit Singal Jun 04 '15 at 22:59

1 Answers1