Python List with Examples – A Complete Python List Tutorial

1. 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.

Python List with Examples - A Complete Python List Tutorial

Python List with Examples – A Complete Python List Tutorial

2. 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.

3. 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

[[‘English’], [‘Gujarati’], [‘Hindi’], ‘Romanian’, ‘Spanish’]

>>> type(languages[0])

<class ‘list’>

A list may also contain tuples or so.

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

(‘English’, ‘Romanian’)

>>> type(languages[0])

<class ‘tuple’>

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

Traceback (most recent call last):

File “<pyshell#24>”, line 1, in <module>

languages[0][0]=’Albanian’

TypeError: ‘tuple’ object does not support item assignment

4. How to Access Python List?

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

>>> days

[‘Monday’, ‘Tuesday’, ‘Wednesday’, 4, 5, 6, 7.0]

Or, you can put it in a print statement.

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

[[‘English’], [‘Gujarati’], [‘Hindi’], ‘Romanian’, ‘Spanish’]

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

>>> languages[0]

[‘English’]

An index cannot be a float value.

>>> languages[1.0]

Traceback (most recent call last):

File “<pyshell#70>”, line 1, in <module>

languages[1.0]

TypeError: list indices must be integers or slices, not float

5. 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]

[‘two’, ‘three’]

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

>>> indices[:4]

[‘zero’, ‘one’, ‘two’, ‘three’]

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

>>> indices[4:]

[‘four’, ‘five’]

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

>>> indices[:]

[‘zero’, ‘one’, ‘two’, ‘three’, ‘four’, ‘five’]

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]

[‘zero’, ‘one’, ‘two’, ‘three’]

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

>>> indices[1:-2]

[‘one’, ‘two’, ‘three’]

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

>>> indices[-2:-1]

[‘four’]

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

>>> indices[-1:-2]

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

6. 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

[‘caramel’, ‘gold’, ‘silver’, ‘occur’]

b. Reassigning a few elements

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

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

[‘caramel’, ‘gold’, ‘bronze’, ‘silver’]

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

[‘caramel’, ‘gold’, ‘bronze’, ‘silver’, ‘occur’]

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

2:2 works too.

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

[‘caramel’, ‘gold’, ‘occur’, ‘bronze’, ‘silver’]

c. Reassigning a single element

You can reassign individual elements too.

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

[‘caramel’, ‘gold’, ‘silver’, ‘bronze’]

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

>>> color[4]='holographic'

Traceback (most recent call last):

File “<pyshell#47>”, line 1, in <module>

color[4]=’holographic’

NameError: name ‘color’ is not defined

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

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

[‘caramel’, ‘gold’, ‘silver’, ‘bronze’, ‘holographic’]

7. 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

Traceback (most recent call last):

File “<pyshell#51>”, line 1, in <module>

colors

NameError: name ‘colors’ is not defined

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

[‘caramel’, ‘gold’, ‘holographic’]

>>> colors[2]

‘holographic’

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

[‘gold’, ‘holographic’]

8. 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

[[‘caramel’, ‘P&B’, ‘Jelly’], [‘onions’, ‘potatoes’], [‘flour’, ‘oil’]]

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

[[[1, 2], [3, 4], 5], [6, 7]]

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

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

4

9. 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

[3, 1, 2, 5, 4, 6]

10. 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

[3, 1, 2, 3, 1, 2, 3, 1, 2]

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

>>> a*3.0

Traceback (most recent call last):

File “<pyshell#89>”, line 1, in <module>

a*3.0

TypeError: can’t multiply sequence by non-int of type ‘float’

b. Membership

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

>>> 1 in a

True

>>> 2 not in a

False

11. 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")

2 is composite

12. 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

[2, 4, 6, 8, 10, 12, 14, 16, 18, 20]

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

[6, 12, 18]

13. Built-in List Functions

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

Python List Tutorial - Built-in List Functions

Python List Tutorial – Built-in List Functions

a. len()

It calculates the length of the list.

>>> len(even)

3

b. max()

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

>>> max(even)

18

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

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

‘3’

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

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

Traceback (most recent call last):

File “<pyshell#116>”, line 1, in <module>

max([2,’1′,’2′])

TypeError: ‘>’ not supported between instances of ‘str’ and ‘int’

c. min()

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

>>> min(even)

6

d. sum()

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

>>> sum(even)

36

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

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

Traceback (most recent call last):

File “<pyshell#112>”, line 1, in <module>

sum(a)

TypeError: unsupported operand type(s) for +: ‘int’ and ‘str’

It works on floats.

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

6.6

e. sorted()

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

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

[1, 2, 3]

>>> a

[3, 1, 2]

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

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

[‘Hello’, ‘hell’, ‘hello’]

Here, since H has an ASCII value of 65, it appears first.

f. c

It converts a different data type into a list.

>>> list("abc")

[‘a’, ‘b’, ‘c’]

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

>>> list(2)

Traceback (most recent call last):

File “<pyshell#122>”, line 1, in <module>

list(2)

TypeError: ‘int’ object is not iterable

g. any()

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

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

True

h. all()

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

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

False

14. 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.

Python List - Built-in Methods

Python List – Built-in Methods

a. append()

It adds an item to the end of the list.

>>> a
[2, 1, 3]
>>> a.append(4)
>>> a[/php]

[2, 1, 3, 4]

b. insert()

It inserts an item at a specified position.

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

[2, 1, 3, 5, 4]

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

[1, 3, 5, 2, 4]

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)

2

>>> a

[1, 3, 5, 4]

e. clear()

It empties the Python list.

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

[]

It now has a False value.

>>> bool(a)

False

f. index()

It returns the first matching index of the item specified.

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

1

g. count()

It returns the count of the item specified.

>>> a.count(3)

2

h. sort()

It sorts the list in an ascending order.

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

[1, 3, 3, 4, 5]

i. reverse()

It reverses the order of elements in the Python lists.

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

[5, 4, 3, 3, 1]

This was all about the Python lists

15. 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

For in-depth Python knowledge, refer Top 10 books of Python.

No Responses

  1. sriyam says:

    Hi All,
    I was asked the below questions in an interview which i could not answer. Can you please provide the answers to me for this.
    1)There is a string such My Name Is Sriyam”. How would i write a program such that it would print the first character of each word in the string. such as M,N,I,S
    2) How can you copy an image from one folder to another in python.

    • Sumit Khajanchi says:

      >>> a = “My Name Is Sumit”
      #We can divide this strings into 4 pieces using split, and then print first character of each.
      >>> for i in a.split(” “):
      print(i[0])
      M
      N
      I
      S

    • Data Flair says:

      Hello, Sriyam
      We Glad you asked your query to us.
      You can use the following piece of code for your first question:
      >>> s=’My Name Is Sriyam’
      >>> for i in s.split(‘ ‘):
      print(i[0])
      As for your second query, you can use shutil. Suppose we have two folders ‘a’ and ‘b’. To move an image ‘df.png’ from ‘a’ to ‘b’, you can:
      >>> shutil.copy(‘a\\df.png’,’b’)
      Now, you can answer every question tossed at you in an interview for Python. We have launched a new series of commonly asked Python Interview Questions and Answers. The series is full of tricky questions so you can prepare yourself for upcoming Python Interviews.

  2. ABDULLAH says:

    It is very useful for me and it’s also be in easy language

    • Data Flair says:

      We are Happy to hear that you like our article on “Python Lists”. We Hope the Slicing List and built-in Functions & Methods help you.
      Each Appreciation Contributes to Our Motivation.

Leave a Reply

Your email address will not be published. Required fields are marked *