Python Tutorial for Beginners 2: Strings - Working with Textual Data

Summary

This video tutorial offers an in-depth exploration of Python's string data type, demonstrating how to create, manipulate, and utilize strings effectively. It covers variable naming conventions, string indexing, slicing, and methods like `lower()`, `upper()`, `count()`, `find()`, and `replace()`. The tutorial also introduces advanced string operations, including formatted strings, f-strings for Python 3.6+, and using `dir()` and `help()` functions to discover available string methods. Aimed at beginners, the video simplifies complex concepts, making Python's string handling accessible and engaging.

Takeaways

• 📝 Python strings are used to represent textual data and are created using single or double quotes.
• 🔡 Python does not require semicolons to end statements; it relies on whitespace for structure.
• 🔑 Variable names in Python should be lowercase with words separated by underscores for readability.
• 📐 The `len()` function in Python is used to find the length of a string.
• 👉 To access individual characters in a string, use indexing with square brackets, starting from index 0.
• ❗ Attempting to access an index that doesn't exist in a string will result in an IndexError.
• 🔄 String methods like `lower()`, `upper()`, `count()`, `find()`, and `replace()` allow for manipulation and analysis of string data.
• 🔑 The `dir()` function can be used to list all methods and attributes available for a given object in Python.
• 📚 The `help()` function provides detailed information about Python's built-in functions and methods.
• 💬 String concatenation can be achieved using the `+` operator or by using formatted strings for more complex constructions.
• 🆕 Python 3.6 introduced f-strings, which simplify the process of inserting variables into strings with ease.

Q & A

What is the purpose of the video?

The video aims to teach viewers about Python data types, specifically focusing on how to work with textual data using strings.

How do you create a variable to hold a text value in Python?

You can create a variable to hold a text value by assigning a string to it, such as `message = 'hello world'`.

Why does Python not require semicolons to end each line?

Python operates on whitespace, making it a clean language to work with, and does not require semicolons to end each line.

What are the conventions for naming variables in Python?

Variables are usually named in lowercase, and if they consist of multiple words, the words are separated by underscores. The names should be descriptive to indicate the value they hold.

How can you include a single quote within a string that uses single quotes?

You can either escape the single quote with a backslash (`\`), or you can use double quotes to enclose the string.

What is the difference between using single quotes and double quotes for strings in Python?

There is no functional difference between using single quotes and double quotes for strings in Python; it depends on the content of the string. If the string contains a single quote, use double quotes to avoid syntax errors and vice versa.

How do you create a multi-line string in Python?

You can create a multi-line string by enclosing the string in triple quotes (`'''` or `"""`).

How do you find the length of a string in Python?

You can find the length of a string using the `len` function, such as `len(message)`.

How do you access individual characters in a string?

You can access individual characters in a string using the index notation with square brackets, such as `message[0]` for the first character.

What is string slicing and how is it done?

String slicing is a way to access a range of characters in a string. It is done using the notation `string[start:stop]`, where `start` is inclusive and `stop` is exclusive.

What are some common string methods in Python?

Common string methods include `.lower()`, `.upper()`, `.count()`, `.find()`, and `.replace()`.

How do you concatenate strings in Python?

You can concatenate strings using the `+` operator, such as `greeting + ', ' + name`, or using formatted strings with placeholders.

What are formatted strings and how are they used?

Formatted strings allow you to create a string with placeholders that are replaced with variable values using the `.format()` method or f-strings (for Python 3.6+).

What are f-strings and how do they work?

F-strings are a way to embed expressions inside string literals using curly braces `{}`. They are prefixed with an `f` or `F` and allow for expressions within the placeholders, like `f'{name.upper()}'`.

How can you find all methods and attributes available to a string variable?

You can use the `dir(variable)` function to list all methods and attributes available to a string variable.

How can you get detailed information about a specific string method?

You can use the `help()` function with the string class and method name, such as `help(str.lower)`, to get detailed information about a specific string method.

What should you do if you want to replace a substring in a string?

Use the `.replace()` method, which takes two arguments: the substring to be replaced and the new substring, such as `message.replace('world', 'universe')`.

Outlines

00:00

📘 Introduction to Python Strings

This paragraph introduces the concept of Python data types, focusing on strings which represent textual data. The script explains how to create a variable to hold text values and the importance of using descriptive variable names following Python's naming conventions. It also touches on Python's whitespace sensitivity and the use of single or double quotes for string literals, including handling strings with quotes within them by escaping or using alternative quotes. Additionally, it covers creating multi-line strings using triple quotes and accessing individual characters within a string using indices.

05:01

🔢 String Manipulation and Methods

The second paragraph delves into string manipulation, starting with the use of the `len()` function to determine the length of a string. It explains how to access individual characters using square brackets and indices, and the concept of slicing to extract substrings. The paragraph also introduces string methods such as `.lower()`, `.upper()`, and `.count()`, demonstrating how to change the case of a string, count occurrences of substrings or characters, and handle errors when accessing non-existent indices.

10:03

🔍 Finding and Replacing String Characters

This section discusses the use of the `find()` and `replace()` methods for locating and substituting characters within strings. It illustrates how the `find()` method returns the starting index of a substring, while the `replace()` method is used to swap out characters or substrings, with attention to the fact that `replace()` does not modify the original string but instead returns a new string with the replacements. The explanation includes the process of assigning the result of `replace()` to a variable to reflect the changes.

15:03

📝 Concatenating and Formatting Strings

The fourth paragraph covers string concatenation using the plus sign operator and introduces the potential pitfalls of forgetting spaces between concatenated strings. It then demonstrates the use of formatted strings with placeholders for variables, utilizing the `.format()` method for a cleaner and more readable approach to string construction. The paragraph also highlights the use of f-strings available in Python 3.6 and above, which allow for simpler and more direct variable insertion within strings, and even the execution of expressions within placeholders.

20:04

🛠️ Exploring Python String Capabilities

The final paragraph provides insights on how to explore and understand the full range of methods and attributes available for strings in Python. It introduces the `dir()` function to list all available methods and attributes for a given object, and the `help()` function to provide detailed documentation on built-in functions and methods. The explanation emphasizes the utility of these functions for quickly accessing information about Python's string capabilities without needing to search online.

Keywords

💡Python

Python is a high-level, interpreted programming language known for its readability and efficiency. In the context of the video, Python is the main subject, with a focus on its data types, particularly strings. The script demonstrates various operations and methods related to Python strings, showcasing the language's capabilities for handling textual data.

💡Strings

In Python, a string is a sequence of characters enclosed in single or double quotes. The video script discusses strings extensively, explaining how they are used to represent textual data. Examples from the script include creating a string with the message 'hello world', manipulating it, and using it in various string methods.

💡Variables

A variable in programming is a storage location paired with an associated symbolic name, which contains some known or unknown quantity or information, a value. In the script, the variable 'message' is used to store the string 'hello world', demonstrating how variables hold data that can be manipulated and used throughout a program.

💡Whitespace

Whitespace in programming refers to any character or series of characters that represent spaces, tabs, or newlines in the text. The script mentions that Python operates on whitespace alone, meaning that the structure of the code is determined by the spaces, tabs, and newlines, rather than by semicolons or other delimiters.

💡Indexing

Indexing is the method of accessing elements in a sequence, such as a string, by their position. The script explains how to access individual characters in a string by using their index numbers, starting with 0 for the first character. For example, accessing the character 'H' in 'hello world' is done by referring to the index 0.

💡Slicing

Slicing is a way to extract a portion of a string by specifying a range of indices. The script demonstrates slicing with the 'hello world' example, showing how to extract the word 'hello' by using a colon to specify the start and end indices, such as message[0:5].

💡Methods

In Python, a method is a function that is associated with an object and is called using the dot notation. The script introduces several string methods, such as 'lower()', 'upper()', 'count()', 'find()', and 'replace()', which are used to perform operations on strings, like changing case, counting characters, or replacing substrings.

💡Concatenation

Concatenation refers to the operation of joining two strings together. The script shows how to concatenate strings using the plus sign operator, such as combining 'hello', a space, and 'world' to form 'hello world'. It also discusses potential issues with concatenation, like forgetting to add spaces between words.

💡Formatted Strings

Formatted strings are strings that contain placeholders for values that are replaced with actual data at runtime. The script introduces the use of formatted strings in Python, where variables can be embedded within a string using curly braces and the 'format' method, making it easier to create readable and complex strings.

💡f-strings

f-strings, introduced in Python 3.6, are a way to embed expressions inside string literals, using curly braces. The script highlights f-strings as a simpler and more efficient method for string formatting, allowing for variables and expressions to be included directly within the string, making the code more readable and concise.

💡dir() and help() functions

The 'dir()' function in Python is used to list the methods and attributes of an object, while the 'help()' function provides documentation strings for objects. The script suggests using 'dir()' to explore available methods for a string and 'help()' to get detailed information about those methods, such as 'upper()' or 'lower()', providing a way for learners to discover and understand Python's capabilities.

Highlights

Introduction to Python data types, focusing on working with textual data (strings).

Demonstration of the print function with a 'Hello World' example.

Explanation of how to create a variable to hold text values.

Discussion on Python's syntax: no need for semicolons, using whitespace for clean code.

Variable naming conventions in Python: lowercase and underscores for multiple words.

Importance of using descriptive variable names for code readability.

Different ways to define strings using single and double quotes.

Handling single quotes within strings by escaping them or using double quotes.

Creating multi-line strings using triple quotes.

Using the len function to find the number of characters in a string.

Accessing individual characters in a string using indexing.

Explanation of string slicing to access a range of characters.

Introduction to string methods such as lower(), upper(), count(), and find().

Replacing parts of a string using the replace() method.

Concatenating strings using the plus sign operator and formatted strings.

Introduction to f-strings in Python 3.6 and above for easier string formatting.

Using dir() and help() functions to explore available string methods and attributes.

Encouragement to ask questions and interact in the comment section.

Suggestions to support the tutorials by liking, sharing, and contributing via Patreon.

Transcripts

Hey there. How's it going everybody in this video?

We'll be learning about python Data types and specifically

We'll be learning about how to work with textual data and textual data in python are represented with strings

So we currently have [opened] our intro pi file that we were working with in the last video

Where we just printed out hello world and I'll go ahead and run this so that we can see that down here

It does print out hello [world] [now]

This line here is using the print function

and we're passing this text value into that print function now if we wanted to create a

Variable that holds that text value then we could say now

I'll just get rid of this comment for now

So if I wanted a variable to hold that value then I can just create a variable and we'll call that

message and we'll set that message variable equal to our text value that we passed in to print and

Here message is our variable [name]

so if you're coming from another [language]

Then you might be wondering if we need [to] use semicolons or something like that to end each line but python doesn't need that it

operates on Whitespace alone

Which makes it a very clean language to work with?

Now by convention our variables are usually all lowercase and if it's multiple words then we separate those with underscore

So if instead my variable name was my message, then it would be my underscore message

So that's just a convention that's commonly used and also these variable names should be as descriptive as possible

As to what values they're meant to hold so message is a good variable name here because it's holding our message

But if I was instead to call this variable m which is a valid variable name

But anyone reading my code now wouldn't know when they see this in variable

What value it's supposed to hold so message is a much better variable name in this case

So this message variable now holds our text data and our text data is called a string now

We can use our variable in place of this string

Anywhere that we use it in our program, so instead [of] printing out hello world

Directly here. I'm instead going to now print out this variable and that should give us the same results

So if I run that then you can see down here, we still get [the] same result now

We can see that

I created this string with single quotes now you can also use double quotes

so if you're wondering if there is a difference between the single quotes in the double quotes

And it really just depends on what text you have in your string

So for example if you have a single quote in your string

So for example let's create one with a single quote instead of hello world, [I] will instead make our string

Bobby's World

Now see the problem [here] is that?

Python sees this single quote within our text as being the end of the string and it's not going to know what to do

With what comes after that single quote here because it thinks that's where the string is closing

So if you run this now then you'll get an error now

There's a couple of different ways to [handle] this we could escape this single quote with a backslash

so if I escape that single quote and now

Run this now python knows that this single quote doesn't close out the string and that instead this one should

Now another way to handle that is [to] instead

So I'll take away that xscape character now another way to handle that is instead

Just use double quotes on the outside of our string any string [that] contains single quotes

So if we know that our string contains a single quote then we can instead use double quotes on the outside

And then it'll know that that single quote isn't the end of the string so now if we run this then we can see that

It still works fine

But that doesn't necessarily mean that double quotes are better because it goes both ways if your string contains double quotes in the message then

I would use single quotes on the outside now if we needed to create a

multi-line string and one way we can do this is by using three quotes at the beginning and end of our string and

these can also be

Single or double quotes as [well], so let's go ahead and look at an example

So I'll add three quotes to the beginning and end of our string here

And now I'll just add [some] text to spans multiple Lines here

so I'll just say was a good and then hit enter to go to a new line and say cartoon in the

1990s so now if we run [that] and we can see that it printed out [our] string correctly over multiple lines, [okay]?

So let's go back to our simple hello world example

So I'm just going to take all of that and replace it with our previous

Hello world example, and now let's go ahead and just run that really quick

So we're back to our starting point so we can think of our string as a string of individual characters

And we can access these individual characters also, so first let's see how we can find how many characters are in our string

So to do this we can use the [len] function which stands for length

So whenever I print out here if I was instead of printing my message if I was to print out this

Length function and pass in message, and then run this. Now we're no longer printing out our message

We're printing out the length of our message

And we can see that it says that the length of our string is 11

And if we counted these up 1 2 3 4 5 6 7 8 9 10 11

Then we can see that that's correct, and we can access our strings characters individually, so to do this we can use the square

Brackets after our string and pass in the location of the character that we want. So, I'll say print

Message and then square brackets now the location is called an index and it starts out at 0

So to access the first character of our string we can say

print the message and then access this index of 0 so if we print that then we can see that we got the

capital H now

since the length of our string is 11 that means that with the first character starting out at 0 our last character would be at

Index 10 so it's our total length minus 1 so if I was to say print out the

Location at Index 10 the value at Index 10 then we can see that we got our d character

Which is the last character in that string.

Now if you accidentally try to access an index that doesn't exist then you'll get an index error. So if we were to say

Access the index of 11, and we can see that that through an index error now

We can also access a range of characters

So if I just wanted to get the word hello from our string then we could say that we want

0 and then this colon 5 and we'll explain this

So the first index here is our starting point and the second in that index which is separated by this colon is

The stopping point now one thing a little confusing about this is that the first index is

Inclusive which means it's going to include that value, but the second index is not now

There's good reasons for this

But it's still easy to forget so basically what we're saying is I want all the characters

Between the beginning and up to but not including the fifth index

And it will be more clear if we just go ahead and run this so we can see that it prints out. Hello

So it printed out our message from the zero index here all the way up to but not including

The [5th] Index here, so we got hello now since our starting point. Here is just [the] first index

We can actually just leave that off and it will assume that we want to start at the beginning

So if we don't put anything there and then : [five] then we should get the same thing

So if we run [that] we can see we still got hello

now instead if we wanted to grab the word world from the string then we could start at

The sixth Index and then we can just go to the end and just like leaving off our

Starting index it will start from the beginning

Leaving off the stop index just goes all the way to the end

So now if we run that and we can see that it gives us back the word world now what we're doing

Here is called slicing and if you'd like to learn more about

Slicing in depth then you can watch my detailed video on that and I'll leave a link to [that] in the [description] section below

So now let's just go back to printing out our message and let me run this okay

So all of the data types that we're going to review are going to have certain methods available to us that give us access to

a lot of useful functionality now when I say methods a lot of people wonder what's the difference between a method and a function and

functions and methods are basically the same thing [a]

Method is just a function that belongs to an object

It's not important to get into the details of that now

But if you hear me say method or function then you can basically think of those as the same thing for now

So like I was saying the data types that we'll be going over all have certain methods

Available to us that give us access to a lot of useful functionality so let's look at some of these string methods

So we can see here that our hello world text is

Capitalized, but let's say [that] we wanted that to be all lowercase now to do this

It's just as easy as saying print message and then to lowercase this we can say dot lower

Now when we run this dot lower with these parentheses here. That's running the lower method on the string

So when we ran that we can see that now our hello world has been set to all lowercase [and] [if] we wanted to do

this to uppercase and it's as easy as changing at

Lower to upper if we run that now we can see that

Hello World is all uppercase?

So now let's say that we want to count a certain number of characters in our string and to do that

We can use the count method and the count method actually takes a string as an argument so we can say

Message dot count and now we have to pass in an argument

And it has to know what we want to count in our message

So what for now?

We'll [just] say count hello

And if we run that we can see that it returns that the string hello appears in our message one time

But if we instead just passed in a single character as argument

So I'll pass in an L if I run that

You can see that we get a 3 because there are three L's and our message variable

So if we instead want to find the index of where certain characters can be found and we can use the find method so I?

Could come up here instead of saying dot count I can say not fine and now this takes an argument as well

It's what we want to find so let me type in world here and run this

And we can see when [we] run this that it returns a six

and that's because world starts at the sixth index of our message variable now if we try to

Find a string of characters that doesn't exist then it will just return negative one

so if instead of world

I typed in universe and ran that you can see it returns a negative one because it can't find that anywhere in our message variable

Okay, so now let's say that we want to replace some characters in our string with some other characters

And we can do this with the replace method now first. I'm going to change this change this back to printing out our

regular message

[so] I'll just delete these

Now let's try to use our replace method right below where we first set our message fair herbal and this method takes two arguments

First it takes what we want to replace so first let me just say message

But replace so first it takes what we want to replace, so let's say that we want to replace

world and now the second argument

Which is separated by a comma [is] what we want to replace world with so we'll replace world with universe

So now if [we] run this and this might be a little unexpected we can see that it's still printing out hello world

[now] the reason our replacement didn't work is because it's not making that replacement in place

It's actually returning a new string with those values replaced and we'll learn more about return statements when we learn about

Functions, but basically we need to set a new variable here

To get that returned string with those replacements, so I could say something like new message is

equal to

That original method with this replacement

So now if we set that

New variable and instead print that new message and run that and you can see that now it replaced the world with

universe

and if you really wanted to make the

Replacement to the message variable then instead of making a new message variable and we can just set this same message

Variable again, so now we're setting the same message variable equal to that replacement and then printing it out

So if I run that and we can see that now the message variable had world

Replaced with universe and this may look a little strange [to] set a variable to an altered [version] of itself

But it's very common, and you'll be using that a lot

Okay, so now let's get rid of this replace line here

And now let's look at how we can add multiple strings and concatenate them together, so instead of saying hello world

I'm instead just going to set this equal to hello and

Instead of calling this message. I'm going to set this equal to greeting and just below greeting

I'm going to create a variable called name and I'm going [to] set that equal to we'll just say

Michael and now lastly let's create a message here and

We want this message to combine our greeting with our name

Wanted to say hello Michael and one way to do this is to use the plus sign operator

so

We could try this by saying greeting plus name now if we run this and we can see that

It's not exactly what we wanted it combined them together, but it doesn't have a space there

So when you're concatenated strings together it's easy to make mistakes like this

So what we want to do is add a string between them so that spaces them out so we can add a string between these

Just by putting in a string literal here

And I'm also going to put in a comma and a space to separate those and now we also need another plus sign

So that we're adding the name after that string so now we're saying that we want this greeting. Which is hello

plus this comma and space plus the name so if I run this

Then we can see that it concatenated those strings together

How we wanted now sometimes using the plus sign isn't the best way to go if we wanted to create a longer more?

Complicated string while using our variables and adding them all together like this

Might get hard to keep track [of] so let's say that we wanted to add to the end of our message

Just by you know closing off a sentence and saying

Welcome so to do that after our name variable

we could add another string that is a period to close off that sentence a space and then

Welcome with an exclamation point so let's go ahead and run that now we can see that it printed out the string

How we wanted it to look?

But it's starting to get a little complicated on this line here to keep track of all of our plus signs and spaces within our

message

instead with strings like this

It's usually better to use a formatted string

[this] allows [us] to write the sentence as it will appear and put placeholders in place of our variables

So let's go ahead and see what this would look like so though instead use a formatted string

We can say message is equal to and we're just going to write it exactly how it appears

Except everywhere where we want to

Replace with a variable we're going to put in a placeholder and those placeholders are going to be these curly brackets

so we want a placeholder for the greeting and then a comma a space and a placeholder for the name [and] a period and then

[we'll] type out welcome and an exclamation point and now to fill those placeholders with our variables

We can say dot

format

And pass in greeting for the first placeholder and [then] name for the second place holder

So now let's go ahead and delete this line where we where we were using the plus sign

Operator so if we run this we can see that

We got the same [thing] as when we concatenate and then together but with longer more complicated strings

This is actually a little bit easier to read it might look a little confusing now

Since we're just seeing these placeholders for the first time but after you get used to this you will realize that this is

Easier than keeping track [of] all those concatenations and using [stream] formatting like this also gives us some extra

Functionality and if you want to see everything [that] you can do with that and I do have a detailed in-depth video on string

Formatting and I'll add that to the description section below

Ok and lastly if you're using python

3.6 or above then you'll have access to these new things called f strings now if you aren't using

[3.6] or higher then these aren't going to work because they were only

Recently released and not a lot of people are using these f strings yet

But I'm really liking them so far

Basically the idea behind f strings was to make string formatting as simple as possible

So let's go ahead and see what these look like so to say that [we] want this to [be] an f string

We can just add an f right here to the beginning on the outside of the string

now instead of using this dot format method well instead just write the variables directly within the

placeholders so [I] can remove that dot format method and now we can pass the

variables directly within the placeholder

So we'll pass

Greeting to that

Placeholder and name to that one so I can save that and run it and you can see that using that we got the same

Result [and] like I said these f strings are pretty new to the language so even people who are very familiar with python

May be seeing this for the first time now one reason

I really like these f strings is because you can actually write code within the placeholder

So if I wanted the name and all caps for some reason then I could just come [into] the placeholder [here]

And say name dot upper and run that directly within the placeholder if I run that

Then you can see that now our name was capitalized, okay?

So we're almost finished up

But I wanted to show you one last trick here when you're learning something new in python

So [we] saw a lot [of] different methods that we could use on our strings now if we ever wanted to see everything

That's available to us then there are a couple of things that we can do so first we can use this

dir function and that looks like this and

what this does is if we pass in A

Variable then it will show us all of the attributes and methods that we have access [to] with [that] variable now

Don't worry about all of these double underscore methods yet, but if we look down here

Then we'll see a couple of familiar methods that we used in this video

[so] for example we have dot upper here we have

not replace

dot lower

So this kind of gives you a broad overview of all the attributes and methods that are [available] to you now

This doesn't show what any of these actually do so to see more information about these string methods

Then we can use the help function

But if we run this help function on the name then that won't work we actually need to run it on the string class

Itself so we'll just type in help and then

Str for string and if I run that and we can see that this gives us a lot more [information]

And I'll pull this up here a bit

so it

You know tells us everything that's available to us, and if I scroll down here [a] bit

And if I try to find something that we actually used in this video okay, so we have fine here

So you can see that actually gives us a description of what these methods do and what arguments they take

Now if you know that you had a certain method available to you

But you couldn't remember exactly what it does then you can actually pass it directly in to help also, so if I wanted to

Find out some more information about the lower method then we could say string dot

Lower and if we run that and we can see that it gives us information and the description just of what lower does

so using that dir function

and that help function is a great way to get a broad overview of the methods and attributes that [are] available to you and

Also, what using the help function gives you an idea of what those?

Methods do without actually you know going online and checking everything there, okay?

So I think that is going to do it for this video

I hope that now you feel comfortable with

Working with strings and are familiar [with] some of the useful things that we can do with those in the next video

We're learning how to work with numbers in python and specifically integers and floats

But if anyone has any [questions] about what we covered in this video

Then feel free to ask in the comment section below and I'll do my [best] to answer those if you enjoy these tutorials and would

Like to support them then there are several ways [you] can do that

The easiest ways to simply like the video and give it a thumbs up and also

it's a huge help to share these videos with

Anyone you think would find them useful and if you have the means you can contribute through patreon

And there's a link to that page in the description section below be sure to subscribe for future videos and thank you all for watching

you