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Python for Basic Data Analysis: 1.5 Lists

Get started on your learning journey towards data science using Python. Equip yourself with practical skills in Python programming for the purpose of basic data manipulation and analysis.

Lists

Lists are a collection of data and are represented with square brackets   [ ]  . With lists, data is stored in sequence.

Lists are mutable, meaning that we can modify and change the content of lists using many methods. Lists can contain different types of data. 

Syntax

listOfFruits = ["apples", "bananas", "cherries"]

In this example, listOfFruits is the variable that we have assigned our list to.

Example

List Indexing

Each element in the list has a specific index. We can access elements in a list via their index. 

The first item in the list has an index of  0 , second item has index of  1  and so on. 

Negative Indexing is when you refer to the items from the end.  -1  refers to the last item,  -2  refers to the second last item and so on. 

 

 

Indexing Example

 

Negative indexing Example

List slicing

To access a range of items in a list, we use the slice operator  : 

Syntax

list[start index:stop index]
list[0:3]

The stop index item will not be included in the range. 

Example

We can add elements to a list using the  append extend  and  insert  methods. Below is how you can apply the methods to your lists. 


Append

We can add a single element to the end of the list using the append method.

Syntax

myList.append("blueberries")

"blueberries" is a string element that we would like to add to the end of myList.

Can we add multiple elements using the  append  method? 

myList.append(["blueberries", "cantaloupes"])

No, append only takes a single item as a parameter. Thus, in this case, blueberries and cantaloupes will be considered as 1 element when appended. 

Example


Extend

We can insert multiple elements to a list using the extend method. 

Syntax

myList.extend(["blueberries", "cantaloupes"])


Example


Insert

We can insert a single element at a specified position in a list using the insert method. 

Syntax

myList.insert(2, "blueberries")

2 represents the index of the element before the new element that you want to insert.
"blueberries" represent the element that you are inserting into the list. 

Example

We can remove elements from a list using the  remove  pop  and  delete  methods. Below is how you can apply the methods to your lists. 


Remove

We can remove a single element as an argument. 

Syntax

myList.remove("cherries")

 

Example


Pop

We can remove an element by referring to its index number. pop() returns the removed element.

Syntax

myList.pop(2)

Example

 

Delete

We can delete an element by referring to its index number.

Syntax

del(myList[2])

Example

Exercises

1. Create and print a list with these elements: Adam, Adora, Ella

2. List indexing: Find the third element in the list

3. List slicing: Access the last 2 items in the list

4. Add these elements to the list using the append and extend methods: Lila, James

5. Insert this element to the list after the second element: Lila

6. Remove Adam from the list

7. Remove the second element from the list using pop and delete

Video Guide