How to add an element in a list inside a list in python?

Question

Say I have 2 lists:

list = [[1, 2, 3], [4, 5]] 
a = 6 

Is there anyway I can put a into the spot list[1][2]?

• doctorlove: Insert or replace?
• Badmephisto: for the program i am writing, i need to add, however i would glad to know how to replace too
• Will: list[1][2] is out of range. list[1] has a length of 2, so you would have to use ppend()
• doctorlove: Now - I was checking what you meant - list[1][2] is the third element of the 2nd list in the list (named \list`)...
• RoadRunner: don't name your list as list, that's an inbuilt function in python.

Answer 1

Yes, you can just do:

lst[1].append(a)
lst
# [[1, 2, 3], [4, 5, 6]]

Answer 2

To add an element, try:

my_list[1].append(a)

To replace an element:

my_list[1][1] = a # This will replace 5 by 6 in the second sub-list

Example of append:

>>> my_list = [[1, 2, 3], [4, 5]]
>>> a = 6
>>> my_list[1].append(a)
>>> my_list
[[1, 2, 3], [4, 5, 6]]

Example of replace:

>>> my_list = [[1, 2, 3], [4, 5]]
>>> a = 6
>>> my_list[1][1] = a
>>> my_list
[[1, 2, 3], [4, 6]]

Note: You should not use list to name your variable, because it would replace the built-in type list.

• Badmephisto: Thank you! I as gonna go look to how to replace elements just now!
• ettanany: @Badmephisto You're welcome, I added also some examples that you can use to understand better!

Answer 3

Instead of using list=[[1,2,3],[4,5]] (since list is a function in python) let's have

l=[[1,2,3],[4,5]] 

Now there is no l[1][2] as yet. If we try to access it we get

>>> l[1][2]
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
IndexError: list index out of range

We can append this element

l[1].append(a)

Now we can access it

>>> l[1][2]
6

and we can change it:

>>> l[1][2] = 44
>>> l
[[1, 2, 3], [4, 5, 44]]