List Functions in Python

List Functions in Python

Ashutosh Mishra's photo
Ashutosh Mishra
·May 12, 2022·

4 min read

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Table of contents

  • 1. Appending an item
  • 2. Find the length of the List
  • 3. Inserting an item in the list
  • 4. Find the index value of an item
  • Conclusion

List is a data structure in Python which allows you to store multiple items in one place. You can think of List as an alternative to Arrays in Python.

We already learned about lists and some common list operations in our last post, if you missed that, you can read it here.

Now let's move ahead and take look at some of the common and useful list functions in Python-

1. Appending an item

In the previous post, we saw how to replace an item in a list. In this post, we will see how to append an item to the list.

Syntax

listname.append(item)

To append an item to a list, you have to use .append() after the name of the list and pass the item you want to insert as an argument. Let's understand this better with an example -

# Let's create a list with a few sample colors
colors = ["Red", "Blue", "Orange", "Pink"]
print(colors) # Expected output - ['Red', 'Blue', 'Orange', 'Pink']
# Now let's add "Purple" to our list
colors.append("Purple") 
print(colors)# Expected output - ['Red', 'Blue', 'Orange', 'Pink', 'Purple']

Explanation

  • In the above code, we first created a color list with a few color names and printed it on the console.
  • Then, we used append() function to add color Purple to our list with the following code - colors.append("Purple")
  • Finally, when we used the print statement this time, we got Purple along with other colors in the list.

2. Find the length of the List

Determining the length of a list is an effortless task in Python. You have to use the len() function.

Syntax

len(listname)

len() function is easy to use, you have to just call the len() and pass the list as an argument. Let's see an example-

# Let's create a list with a few sample colors
colors = ["Red", "Blue", "Orange", "Pink"]
print(len(colors)) # Expected output - 4

Explanation

  • Just like the previous snippet, we first created a color list.
  • After that, we printed the len(colors) function to know the length of the list. To determine the length of a list, you have to pass the list name inside the len() function.

3. Inserting an item in the list

We have already seen how to replace a particular item in the list. Now we will see, how to insert an item in a particular position.

Syntax

listname.insert(index, item)

To insert an item at a particular position on the list, we have to add .insert() after the name of the list and pass 2 arguments to the function - the index position at which we want to insert our item and the item itself. See the below example -

# Let's create a list with a few sample colors
colors = ["Red", "Blue", "Orange", "Pink"]
print(colors) # Expected output - ['Red', 'Blue', 'Orange', 'Pink']
# Now let's add color "Purple" on the index postion 2
colors.insert(2, "Purple")
print(colors) # Expected output - ['Red', 'Blue', 'Purple', 'Orange', 'Pink']

Explanation

  • After creating and printing the color list, we used the insert() function to add the color Purple on the index position 2 in our list.
  • We used colors.insert(2, "Purple") which inserted the "Purple" on the 2nd index position.

Inserting an item on a certain index position does not replace the previous item, it only shifts it and other subsequent items to their next positions.

4. Find the index value of an item

Every item in a list has an index position. When working on a complex project, you may need to determine the index position of a value. The index() function comes to help here. It helps you identify the index position of an item in the list.

Syntax

listname.index(item)

To identify the index position of an item, you have to add .index after the listname and pass the item as an argument. Let's understand this better with an example-

# Let' create a list with a few sample colors
colors = ["Red", "Blue", "Orange", "Pink"]
# Now let's identify the position of the color "Blue"
print(colors.index("Blue")) # Expected output - 1

Exaplanation

  • In the above code, we created a color list and used the index() function on it and passed "Blue" as an argument.
  • The code in return gave us the index position of the color "Blue", i.e., 1.

Conclusion

That's it for today's post and I will see you soon in another Python tutorial. This tutorial and all the future tutorials in this series are based on The Complete Python Masterclass. Check out this course if you want to learn Python in detail.

Happy Coding!

 
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