Insert an Element at a Specific Index in a List and Return the Updated List

Insert an element at a specific index in a list and return the updated list

The shortest I got: b = a[:2] + [3] + a[2:]

>>>
>>> a = [1, 2, 4]
>>> print a
[1, 2, 4]
>>> b = a[:2] + [3] + a[2:]
>>> print a
[1, 2, 4]
>>> print b
[1, 2, 3, 4]

Insert element into list at specific index

Use the list.insert function:

list.insert(index, element)

How to insert list at specific position into list of lists

You can insert in a list of lists like

list_of_lists[2].insert(4,list_to_insert)

However in the output you gave the element isn't inserted rather replaced.
So to get that output

list_of_lists[2][4]=list_to_insert

how to insert a element at specific index in python list

When you insert something into a empty list, it will always be starting from the first position. Do something like this as workaround:

somelist=[]
somelist.insert(0,"dummy")
somelist.insert(1,"Jack")
somelist.insert(2,"Nick")
somelist.insert(3,"Daniel")

#print(somelist[1])
print(somelist[1])

output:

Jack

Inserting a Value in List by Index

In your code you are calling two different methods for adding items to a list. First you call bookList.append() which appends the item to the end of the list. The return value of append() is always None. When you call insert() you are inserting that return value. To fix your code, just remove the call to bookList.append() and assign the return value of the input() to item:

def insertBookByPosition():
    pos = int(input("Select insert location: "))
    adjpos = pos + 1

    item = input("Insert item: ")
    bookList.insert(adjpos, item)

    print("Revised list: " + str(bookList))

How to insert a list at a specific index?

You can use list.insert which takes the index as the first argument

>>> a=[1,2,3]
>>> b=[[1,2],[3,4,5]]
>>> b.insert(1, a)
>>> b
[[1, 2], [1, 2, 3], [3, 4, 5]]

How to insert an item into an array at a specific index (JavaScript)

You want the splice function on the native array object.

arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert).

In this example we will create an array and add an element to it into index 2:

var arr = [];
arr[0] = "Jani";
arr[1] = "Hege";
arr[2] = "Stale";
arr[3] = "Kai Jim";
arr[4] = "Borge";

console.log(arr.join()); // Jani,Hege,Stale,Kai Jim,Borge
arr.splice(2, 0, "Lene");
console.log(arr.join()); // Jani,Hege,Lene,Stale,Kai Jim,Borge

Python list insert with index

If your values are unique, could you use them as keys in a dictionary, with the dict values being the index?

a={}
nums = [1,4,5,7,8,3] 

for num in nums:
    a.update({str(num): num})

sorted(a, key=a.get)

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