Python List with Examples – A Complete Python List Tutorial

In today’s tutorial, we will learn about Python list. We will discuss how to create, access, slice, and reassign list in Python. Then we will see how to apply functions to them.  Along with this, we will discuss Python List Operations and Concatenation.

So, let’s start the Python List Tutorial.

What is Python List?

Unlike C++ or Java, Python Programming Language doesn’t have arrays. To hold a sequence of values, then, it provides the ‘list’ class. A Python list can be seen as a collection of values.

1. How to Create Python List?

To create python list of items, you need to mention the items, separated by commas, in square brackets. This is the python syntax you need to follow. Then assign it to a variable. Remember once again, you don’t need to declare the data type, because Python is dynamically-typed.

>>> colors=['red','green','blue']

A Python list may hold different types of values.

>>> days=['Monday','Tuesday','Wednesday',4,5,6,7.0]

A list may have python list.

>>> languages=[['English'],['Gujarati'],['Hindi'],'Romanian','Spanish']
>>> languages

Output

>>> type(languages[0])

Output

A list may also contain tuples or so.

>>> languages=[('English','Albanian'),'Gujarati','Hindi','Romanian','Spanish']
>>> languages[0]

Output

>>> type(languages[0])

Output

>>> languages[0][0]='Albanian'

Output

2. How to Access Python List?

To access a Python list as a whole, all you need is its name.

>>> days

Output

Or, you can put it in a print statement.

>>> languages=[['English'],['Gujarati'],['Hindi'],'Romanian','Spanish']
>>> print(languages)

Output

To access a single element, use its index in square brackets after the list’s name. Indexing begins at 0.

>>> languages[0]

Output

An index cannot be a float value.

>>> languages[1.0]

Output

3. Slicing a Python List

When you want only a part of a Python list, you can use the slicing operator [].

>>> indices=['zero','one','two','three','four','five']
>>> indices[2:4]

Output

This returns items from index 2 to index 4-1 (i.e., 3)

>>> indices[:4]

Output

This returns items from the beginning of the list to index 3.

>>> indices[4:]

Output

It returns items from index 4 to the end of the list in Python.

>>> indices[:]

Output

This returns the whole list.

• Negative indices- The indices we mention can be negative as well. A negative index means traversal from the end of the list.

>>> indices[:-2]

Output

This returns item from the list’s beginning to two items from the end.

>>> indices[1:-2]

Output

It returns items from the item at index 1 to two items from the end.

>>> indices[-2:-1]

Output

This returns items from two from the end to one from the end.

>>> indices[-1:-2]

Output

This returns an empty Python list, because the start is ahead of the stop for the traversal.

4. Reassigning a Python List (Mutable)

Python Lists are mutable. This means that you can reassign its items, or you can reassign it as a whole. Let’s take a new list.

>>> colors=['red','green','blue']

a. Reassigning the whole Python list

You can reassign a Python list by assigning it like a new list.

>>> colors=['caramel','gold','silver','occur']
>>> colors

Output

b. Reassigning a few elements

You can also reassign a slice of a list in Python.

>>> colors[2:]=['bronze','silver']
>>> colors

Output

If we had instead put two values to a single one in the left, see what would’ve happened.

>>> colors=['caramel','gold','silver','occur']
>>> colors[2:3]=['bronze','silver']
>>> colors

Output

colors[2:3] reassigns the element at index 2, which is the third element.

2:2 works too.

>>> colors[2:2]=['occur']
>>> colors

Output

c. Reassigning a single element

You can reassign individual elements too.

>>> colors=['caramel','gold','silver','occur']
>>> colors[3]='bronze'
>>> colors

Output

Now if you want to add another item ‘holographic’ to the list, we cannot do it the conventional way.

>>> colors[4]='holographic'

Output

So, you need to reassign the whole list for the same.

>>> colors=['caramel','gold','silver','bronze','holographic']
>>> colors

Output

3. How can we Delete a Python List?

You can delete a Python list, some of its elements, or a single element.

a. Deleting the entire Python list

Use the del keyword for the same.

>>> del colors
>>> colors

Output

b. Deleting a few elements

Use the slicing operator in python to delete a slice.

>>> colors=['caramel','gold','silver','bronze','holographic']
>>> del colors[2:4]
>>> colors

Output

>>> colors[2]

Output

Now, ‘holographic’ is at position 2.

c. Deleting a single element

To delete a single element from a Python list, use its index.

>>> del colors[0]
>>> colors

Output

Multidimensional Lists in Python

You can also put a list in a list. Let’s look at a multidimensional list.

>>> grocery_list=[['caramel','P&B','Jelly'],['onions','potatoes'],['flour','oil']]
>>> grocery_list

Output

This is a grocery Python list with lists in it, where the lists are according to a category.

Or, you can choose to go deeper.

>>> a=[[[1,2],[3,4],5],[6,7]]
>>> a

Output

To access the element 4 here, we type the following code into the shell.

>>> a[0][1][1]

Output

Concatenation of Python List

The concatenation operator works for lists as well. It lets us join two lists, with their orders preserved.

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

Output

Python List Operations

a. Multiplication

This is an arithmetic operation. Multiplying a Python list by an integer makes copies of its items that a number of times while preserving the order.

>>> a*=3
>>> a

Output

However, you can’t multiply it by a float.

>>> a*3.0

Output

b. Membership

You can apply the ‘in’ and ‘not in’ operators on a Python list.

>>> 1 in a

Output

>>> 2 not in a

Output

Iterating on a list

Python list can be traversed with a for loop in python.

>>> for i in [1,2,3]:
         if i%2==0:
                print(f"{i} is composite\n")

Output

Python List Comprehension

You can create a new list just like you would do in mathematics. To do so, type an expression followed by a for statement, all inside square brackets. You may assign it to a variable. Let’s make a list for all even numbers from 1 to 20.

>>> even=[2*i for i in range(1,11)]
>>> even

Output

Optionally, you can add an if-statement to filter out items. If we want to change this list to hold only those items from 1 to 20 that are even and are divisible by 3, we write the following code.

>>> even=[2*i for i in range(1,11) if i%3==0]
>>> even

Output

Built-in List Functions

There are some built-in functions in Python that you can use on python lists.

a. len()

It calculates the length of the list.

>>> len(even)

Output

b. max()

It returns the item from the list with the highest value.

>>> max(even)

Output

If all the items in your list are strings, it will compare.

>>> max(['1','2','3'])

Output

But it fails when some are numeric, and some are strings in python.

>>> max([2,'1','2'])

Output

c. min()

It returns the item from the Python list with the lowest value.

>>> min(even)

Output

d. sum()

It returns the sum of all the elements in the list.

>>> sum(even)

Output

However, for this, the Python list must hold all numeric values.

>>> a=['1','2','3']
>>> sum(a)

Output

It works on floats.

>>> sum([1.1,2.2,3.3])

Output

e. sorted()

It returns a sorted version of the list, but does not change the original one.

>>> a=[3,1,2]
>>> sorted(a)

Output

>>> a

Output

If the Python list members are strings, it sorts them according to their ASCII values.

>>> sorted(['hello','hell','Hello'])

Output

Here, since H has an ASCII value of 72, it appears first.

f. list()

It converts a different data type into a list.

>>> list("abc")

Output

It can’t convert a single int into a list, though, it only converts iterables.

>>> list(2)

Output

g. any()

It returns True if even one item in the Python list has a True value.

>>> any(['','','1'])

Output

It returns False for an empty iterable.

>>> any([])

Output

h. all()

It returns True if all items in the list have a True value.

>>> all(['','','1'])

Output

It returns True for an empty iterable.

>>> all([])

Output

Built-in Methods

While a function is what you can apply on a construct and get a result, a method is what you can do to it and change it. To call a method on a construct, you use the dot-operator(.). Python supports some built-in methods to alter a Python list.

a. append()

It adds an item to the end of the list.

>>> a

Output

>>> a.append(4)
>>> a

Output

b. insert()

It inserts an item at a specified position.

>>> a.insert(3,5)
>>> a

Output

This inserted the element 5 at index 3.

c. remove()

It removes the first instance of an item from the Python list.

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

Output

Notice how there were two 2s, but it removed only the first one.

d. pop()

It removes the element at the specified index, and prints it to the screen.

>>> a.pop(3)

Output

>>> a

Output

e. clear()

It empties the Python list.

>>> a.clear()
>>> a

Output

It now has a False value.

>>> bool(a)

Output

f. index()

It returns the first matching index of the item specified.

>>> a=[1,3,5,3,4]
>>> a.index(3)

Output

g. count()

It returns the count of the item specified.

>>> a.count(3)

Output

h. sort()

It sorts the list in an ascending order.

>>> a.sort()
>>> a

Output

i. reverse()

It reverses the order of elements in the Python lists.

>>> a.reverse()
>>> a

Output

This was all about the Python lists

Python Interview Questions on Lists

1. What are lists in Python? Explain with example.
2. How to get the elements of a list in Python?
3. How to make a list in a list Python?
4. What are lists used for in Python?
5. What are lists called in Python?

Conclusion

Woah, that was a lot, wasn’t it? Let’s make a quick revision so you don’t forget it.

In this lesson on Python Lists, we first looked at how to declare and access a list. That included slicing lists in python. Then we looked at how to delete and reassign elements or an entire list.

Next, we learned about multidimensional lists and comprehension. We saw how to iterate on python lists, concatenate them, and also the operations that you can perform on them.

Lastly, we looked at some built-in functions and methods that you can call on lists. Hope you enjoyed, see you again.

Furthermore, if you have any query, feel free to ask in the comment section