How to append to the end of an empty list

Question

I have a list   list1      the length of the list is undetermined so I am trying to append objects to the end of list1 like such   for i in range 0  n        list1 list1 append  i     But my output keeps giving this error  AttributeError   NoneType  object has no attribute  append   Is this because list1 starts off as an empty list  How do I fix this error

User · Answer

Mikola has the right answer but a little more explanation   It will run the first time  but because append returns None  after the first iteration of the for loop  your assignment will cause list1 to equal None and therefore the error is thrown on the second iteration

User · Answer

append returns None  so at the second iteration you are calling method append of NoneType  Just remove the assignment   for i in range 0  n       list1 append  i

User · Answer

Note that you also can use insert in order to put number into the required position within list   initList    1 2 3 4 5  initList insert 2  10    insert pos  val    gt  initList    1 2 10 3 4 5    And also note that in python you can always get a list length using method len

User · Answer

You don t need the assignment operator   append returns None

User · Answer

append actually changes the list  Also  it takes an item  not a list  Hence  all you need is  for i in range n      list1 append i     By the way  note that you can use range n   in this case    I assume your actual use is more complicated  but you may be able to use a list comprehension  which is more pythonic for this   list1    i for i in range n     Or  in this case  in Python 2 x range n  in fact creates the list that you want already  although in Python 3 x  you need list range n

User · Answer

I personally prefer the   operator than append   for i in range 0  n        list1      i     But this is creating a new list every time  so might not be the best if performance is critical

User · Answer

use my list append      and do not use and other list to append as list are mutable

User · Answer

Like Mikola said  append   returns a void  so every iteration you re setting list1 to a nonetype because append is returning a nonetype   On the next iteration  list1 is null so you re trying to call the append method of a null   Nulls don t have methods  hence your error

[python] How to append to the end of an empty list?

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