Help! Python programmers.

IreshMM · Sep 20, 2015

Actually, I'm not an expert. So I need your help to understand this.

Code:

lst=[4, 5, 5, 4]
nwlst=lst
for i in lst:
    print i
    nwlst.remove(i)

Expected result :
4
5
5
4

but I got :

4
5

Once I removed the statement : nwlst.remove(i)
I got the expected result.

Can anyone explain this? How this happens? :confused:

charith84 · Sep 20, 2015

because when you call lst.remove(i) to remove an element from the array "lst" it will remove all the elements which equals to the i
eg
4, 5, 5, 4
nwlst.remove(4):give you the result "5,5" (removed all "4" s in the array)
try to remove it by array index

nismok · Sep 20, 2015

list.remove(x) will remove given value (x) from the list. Use del or pop to remove index.

https://docs.python.org/2/tutorial/datastructures.html

homoelectronics · Sep 20, 2015

I think since list is an object, nwlst = lst makes them refer to the same list object. (Pass by reference)

IreshMM · Sep 20, 2015

charith84 said:
because when you call lst.remove(i) to remove an element from the array "lst" it will remove all the elements which equals to the i
eg
4, 5, 5, 4
nwlst.remove(4):give you the result "5,5" (removed all "4" s in the array)
try to remove it by array index

It removed only the first element.

nwlst.remove(i) has been called not lst.remove(i)

Can you check that again?