Python insert() function printing the list the opposite way

[Steve389]

[CODE lang="python" title="Insert() function confusion" highlight="3-4"]myList = [] # creating an empty list

for i in range(5):
myList.insert(0, i + 1)

print(myList)[/CODE]

I am new to Python and I am wondering why this outputs the numbers backwards. Surely it starts from 0 and not from the last value?

 

[LTomy]

I did not understand. Right now, it starts at 0 or 6? Seems like it should start at 6.

When you give '0' as first argument to 'insert', you insert the value at the start of the array.
Therefore, in the 'for' loop, the array grows like that:
(1)
(2, 1)
(3, 2, 1)
(4, 3, 2, 1)
...

 

[Steve389]

[5, 4, 3, 2, 1]

Idk if this helps but this is the output. I am confused why it produces 5 and counts down, I would have thought it would start at 1 and move up?

 

[LTomy]

In the 'for' loop above, 'i' starts with the value '1' up until 5'.

So, in the first iteration, you insert '1' at the begining of the list.
Then, you insert '2' at the START of the list.
...
Finally, '6' is inserted at the START of the list.

The first argument of 'insert' is the position inside the list where you want to insert the value. If you give '0', then it will be inserted at the beginning of the list.

If you want to add values at the end of the list, use 'append':
myList.append(i)

 

[Steve389]

I didn't even think about it like that! thank you!!

 

[Steve389]

Sorry to bug you with more questions but I am quite curious.

myList = [] # creating an empty list

for i in range(5):
    myList.insert(2, i + 1)

print(myList)

If I do it this way it outputs

[1, 2, 5, 4, 3]

Is this because it's just printing every value up until it reaches 5 then the only thing it has left is 2 then 1 so that's why it prints them?

 

[LTomy]

Print will simply display the values inside the List, in order. When you give '2' as first argument to 'insert', the value is inserted inside the array at the index 2 from the start of the list. If the list is smaller than 3, then it is inserted at the end.