Introduction To Lists In Python (Python Tutorial #4)

Summary

This video from CS Dojo introduces Python lists, a versatile data structure similar to arrays in other languages. It demonstrates how to define, append, and manipulate lists, including adding mixed types and nested lists. The tutorial covers common list methods like 'append', 'pop', and indexing, and provides a practical exercise to swap elements within a list. The video also offers resources for further learning and support.

Takeaways

• 📝 Introduction to Lists: The script introduces lists in Python, a data type used to store a collection of items similar to arrays in other languages.
• 🔑 Defining a List: A list in Python can be defined using square brackets, with elements separated by commas.
• 📈 Appending Items: The 'append()' method is used to add items to the end of a list.
• 🔄 Type Flexibility: Python lists can contain elements of different data types, including numbers, strings, and even other lists.
• 📚 Nested Lists: A list can include another list as an element, creating a nested structure.
• ➖ Removing Items: The 'pop()' method removes the last item from a list, but can also be used to remove an item at a specific index.
• 🔑 Indexing: Items in a list can be accessed using zero-based indexing, with the first item at index 0.
• 🛠 Modifying Items: Elements in a list can be changed by selecting the item with its index and assigning a new value to it.
• 🔍 Retrieving Items: Specific items in a list can be retrieved using their index within square brackets.
• 🔄 Swapping Elements: The script demonstrates how to swap two elements in a list using temporary variables or a shortcut method.
• 📌 Additional Methods: The script mentions that there are many other predefined functions for lists in Python, with 'append()' and 'pop()' being among the most common.
• 📚 Learning Resources: The video provides a link to download sample files and suggests using an IDE like PyCharm for Python development.
• 🤝 Community Support: The script encourages viewers to support the channel through Patreon and provides a link for the same.

Q & A

What is a list in Python?

A list in Python is a type of data structure similar to arrays in other languages, used to store a collection of items.

How do you define a list in Python?

You can define a list in Python by using square brackets and separating elements with commas, e.g., a = [3, 10, -1].

Can you provide an example of how to assign a list to a variable in Python?

Yes, you can assign a list to a variable using the syntax 'variable_name = [elements]'. For example, 'a = [3, 10, -1]' assigns a list with the elements 3, 10, and -1 to the variable 'a'.

How can you add an item to a list in Python?

You can add an item to a list using the 'append()' method, like 'a.append(1)', which appends the number 1 to the list 'a'.

What is the dot notation used for in Python lists?

The dot notation in Python is used to call methods on objects. For lists, it is used to call predefined functions like 'append()' and 'pop()'.

Can you mix different data types in a single list in Python?

Yes, Python lists are dynamic and can contain elements of different data types, such as numbers and strings.

How do you append a string to a list in Python?

You can append a string to a list using the 'append()' method followed by the string in quotes, like 'a.append("hello")'.

What is the purpose of the 'pop()' method in Python lists?

The 'pop()' method is used to remove and return the last item from a list. It can also be used with an index to remove an item at a specific position.

How can you retrieve a specific item from a list in Python?

You can retrieve a specific item from a list using indexing, e.g., 'a[0]' retrieves the first item in the list 'a'.

How do you change the content of a list item in Python?

You can change the content of a list item by indexing the item with its position and assigning a new value to it, like 'a[0] = 100' changes the first item to 100.

What is the concept of a nested list in Python?

A nested list in Python is a list that contains other lists as its elements. It allows for more complex data structures within a list.

Can you provide an example of how to swap two elements in a list in Python?

Yes, you can use a temporary variable to hold one element and then swap the elements using their indices, e.g., 'temp = b[0]; b[0] = b[2]; b[2] = temp' swaps the first and last elements of the list 'b'.

Is there a shortcut for swapping two elements in a list in Python?

Yes, you can swap two elements in a list using a single line of code: 'b[0], b[2] = b[2], b[0]', which directly swaps the elements without the need for a temporary variable.

Where can I find the sample file mentioned in the video script?

You can download the sample file by visiting the website 'CSdojo.io/Python4'.

What is the recommended IDE for Python mentioned in the script?

The script recommends using 'PyCharm' as a good IDE for Python.

How can I support the creator of the video?

You can support the creator through Patreon by visiting 'CSdojo.io/PT'.

Outlines

00:00

📝 Introduction to Python Lists

This paragraph introduces the concept of lists in Python, comparing them to arrays in other languages like Java. It demonstrates how to define a list with elements and assign it to a variable. The speaker also mentions the availability of a sample file for download and the option to use an IDE like PyCharm for Python development. The paragraph covers basic list operations such as appending items with the 'append' method and mixing different data types within a single list. It also shows how to add a nested list and delete items using the 'pop' method.

05:03

🔄 Manipulating Python Lists

The second paragraph delves into more advanced list manipulation techniques in Python. It explains how to retrieve specific items using indexing and change the content of a list by directly assigning new values to indexed positions. The speaker provides an exercise problem to swap the first and last elements of a list, offering a step-by-step solution involving temporary variables and demonstrating an alternative shortcut method for swapping. The paragraph concludes with a reminder about downloading sample files and supporting the channel through Patreon.

Keywords

💡List

A 'List' in Python is a versatile data structure that can be used to store a collection of items. In the video, it is introduced as a type of data similar to strings and integers, and it is used to demonstrate how to store a series of elements such as numbers and strings. The script uses the example of creating a list with the elements 3, 10, and -1, which shows the list's ability to hold multiple items.

💡Data Type

A 'Data Type' refers to the classification of data in terms of what type of value the data holds. In the context of the video, lists, strings, and integers are all data types in Python. The script explains that lists are used to store a list of things, which differentiates them from other data types like strings that hold text or integers that hold whole numbers.

💡Array

An 'Array' is a data structure used in many programming languages, including Java, to store a fixed-size sequential collection of elements of the same type. The video script mentions arrays to draw a comparison with Python lists, noting the similarity in storing ordered collections of items, but also highlighting the flexibility of Python lists to contain mixed data types.

💡Append

'Append' is a method in Python that is used to add an item to the end of a list. The script demonstrates the use of the append method with the statement 'a.append(1)', showing how the number 1 is added to the existing list, thus expanding its contents.

💡Dot Notation

'Dot Notation' refers to the syntax used in object-oriented programming to access attributes or methods of an object. In the script, dot notation is used when calling the append and pop methods on a list, such as 'a.append(1)' and 'a.pop()', indicating the use of these methods on the list object 'a'.

💡Mixed Types

The term 'Mixed Types' is used in the script to describe the ability of Python lists to contain elements of different data types within the same list. This is demonstrated by appending a string 'hello' to a list that already contains numbers, showcasing the flexibility of Python lists compared to arrays in some other languages.

💡Nested List

A 'Nested List' is a list that is an element of another list. In the video script, a nested list is created and appended to list 'a' with the syntax '[1, 2]', and then it is added to the list, illustrating how lists can contain other lists as elements.

💡Pop

'Pop' is a method used in Python to remove the last item from a list. The script shows the use of the pop method with 'a.pop()', which removes the last element from the list 'a', demonstrating how to delete items from a list.

💡Index

An 'Index' in the context of lists in Python refers to the position of an item within the list. The script explains that indices start at 0, with the first item having an index of 0, the second item an index of 1, and so on. This concept is used to retrieve specific items from a list, such as 'a[0]' to get the first item.

💡Assignment

In programming, 'Assignment' is the process of assigning a value to a variable. In the script, assignment is used to change the content of a list by first selecting an item with its index and then assigning a new value to it, as shown with 'a[0] = 100', which changes the first item in the list from its original value to 100.

💡Swap

'Swap' refers to the action of exchanging the positions of two elements. The script provides an exercise to swap the first and last elements in a list, demonstrating the use of temporary variables and index manipulation to achieve the swap, and also showing a shortcut method using simultaneous assignment.

Highlights

Introduction to lists in Python as a type of data used to store a list of items.

Lists are similar to arrays in other languages like Java.

Defining a list with elements 3, 10, and -1 using square brackets.

Downloading sample files from CSdojo.io for Python learning.

Using an IDE like PyCharm for Python development instead of Jupyter Notebook.

Using the append() method to add an item to a list.

Dot notation is commonly used in Python for predefined functions on data types.

Mixing different data types within a single list in Python.

Appending a string 'hello' to a list containing numbers.

Appending a nested list to an existing list.

Using the pop() method to delete the last item of a list.

Deleting a specific item using the pop() method with its index.

Retrieving a specific item from a list using indexing.

Changing the content of a list item by selecting and reassigning its value.

Exercise problem to swap the first and last items of a list.

Using a temporary variable to swap elements within a list.

Shortcut method to swap elements using simultaneous assignment.

Visualizing a list as compartments for easier understanding of list manipulation.

Final reminder to visit CSdojo.io for resources and support through Patreon.

Transcripts

hey CS dojo in this video I'm gonna

introduce you to list in Python the list

is a type of data just like strings and

integers that we've seen so far and it's

used to store a list of things and it's

similar to arrays in some other

languages like Java so let's take a look

at one example here to define a list you

can just write a equals open square

bracket 3 comma 10 comma minus 1 close

square bracket and this line means

define a new list with the elements 3 10

and minus 1 and assign this list to this

variable a and just a quick note here

that you can download this sample file

by going to CS no 2 dot io / Python 4

and another quick reminder that you

don't necessarily have to use Jupiter

notebook to follow this course you could

use for example per charm which is a

good IDE for Python now let's run the

cell and once we run the cell a should

be defined so let's print a with print

parentheses a and we see that we get a

list with the elements 3 10 and minus 1

what if we wanted to add an item to this

list you can do that with a dot append

parentheses 1 this means append the item

the number one to the list 8 so this dot

notation is a pretty common one and

you'll see more of that later in this

course so this function append is

basically a predefined function that you

can use on the list datatype so again

that's a dot append parentheses one

let's execute this cell and once we

print a you see that the number 1 has

been added to this list so one

interesting thing about the Python list

which is different from some other

languages like Java is that you can mix

types in a single list so you could have

a list containing numbers as well as a

string let's see how that works by

appending the string hello to the list a

with a dot a pen

parentheses double quotes hello let's

print that with print a execute this

cell and you see that this list now

contains hello the string as well as the

numbers a list could even contain

another list so let's see how that works

with ADA app in square brackets 1 comma

2 so this means create a new list with

the elements 1 & 2 and then append it to

this list let's see how that looks with

print parentheses a and let's run this

cell and now you see that we have a

bunch of numbers and then a string which

is hello and another list within the

single list okay what if you wanted to

delete an item from this list for

example the last item to delete the last

item you can do a dot pop parentheses so

we're using the dot notation again here

and pop is another function that's

predefined for the list datatype and

that's why we can just write a dot pop

open parentheses close parentheses and

to see the result you can of course

print a and let's run the cell and you

see that a now has the numbers and the

string but not the list because that's

popped or deleted

let's delete the string as well this

Hello string with a dot pop which still

is the last item of the list of course

and then let's print a and you see that

it now has numbers only now there are

many other predefined functions other

than pop and a pen on the list data type

but a pen and pop are two of the most

common ones okay what if you wanted to

retrieve a specific item from this list

for example the first item the second

item or the third item to do that you

can just write a square brackets 0 and

this means retrieve the item from the

list a with the index 0 and in Python

just like in many other languages the

index starts at 0 so the first item in a

list has the index 0 and the second item

as the next one the third item has the

index 2 and so on ok so we want to print

this item just to make sure we got the

right one but actually interpreter

notebook you don't have to use the print

statement every time you could just

write a square bracket 0 here and when

you run this cell you get the first item

in the list but to keep it consistent

and also to make sure it works in any

other platform for example Park charm

I'm gonna use the print statement every

time okay what if you wanted to retrieve

the fourth item this number one to do

that you can just do a square brackets 3

so the fourth item has the index 3 and

then let's print that and we get 1 and

what if you wanted to change the content

of this list so what if we wanted to

change this number 3 to 100 to do that

you can first select that item with a

square bracket 0 that's the first item

in the list and then you can assign a

new number or any new value to it with a

square bracket 0 equals 100 let's run

this cell and then let's print a again

with print parentheses a and you see

that the first value of this list is 100

now instead of 3 okay now I'm gonna give

you a quick exercise problem to practice

what you've learned so far let's say you

have a list with three strings inside so

you have B equals square brackets double

quotes banana comma double quotes Apple

comma and then Microsoft can you swap

the first value of this list whose index

is of course 0 with the last item of

this list before I show you my solution

to this problem I'm going to show you a

model you can use for thinking about a

list in Python when you have B equals

banana Apple Microsoft the way you can

think about it is that B is going to be

sort of like three boxes put together or

one giant box one long box

with three compartments and each of

those compartments acts like a variable

so each of those refers to a value in

this case the first compartment refers

to banana and the second element refers

to Apple and the third element of course

refers to the string Microsoft and I'm

going to show you my solution first

right temp equals B square brackets 0 so

we're defining a new variable called

temp for a temporary variable which is

going to refer to what B square bracket

0 refers to which is this one and then

you can write B square bracket 0 equals

B square brackets 2 so we're saying the

first compartment should now refer to

whatever the third compartment refers to

because like I said the index for the

first item is 0 and the index for the

second item is 1 and the index for the

third item is 2 so after this line the

first compartment or the first element

will now refer to what the third

compartment refers to which is Microsoft

and once you have that you can write B

square brackets 2 equals temp and the

third compartment now will refer to what

temp refers to which is banana as a

result after these pieces of code we

have the desired result so that's a list

with the first compartment referring to

the value Microsoft and the second

element being Apple and the third

element being banana the string ok let's

make sure that method works in code

first print the current lists with print

B and we have banana Apple and Microsoft

just like we saw will first define a

temporary variable with temp equals B

square bracket 0 and then assign the

value of B square brackets 2 to be

square brackets 0 and then assign what

temp refers to to be square brackets 2

and then at the end we're going to print

B

okay that's correct we have Microsoft

Apple banana now and actually there's a

shortcut for this and that's B square

brackets 0 comma B square brackets 2

equals B square brackets 2 comma B

square brackets 0 let's see if that

works by printing B and once we print be

the first element and the last element

should be swapped again so we should get

the same list as the first one banana

Apple and Microsoft and that's what we

get so this is definitely a valid way to

swap two variables or two elements

within a list but don't worry too much

about this particular method okay just a

quick reminder you can go to CH dojo dot

io / Python for to download the sample

file and the best way to support me

would be through my patreon page and you

can find that at CH dojo dot IO / PT ok

I'm working from CH dojo and I'll see

you guys in the next video