Using Python String Methods

15 minutes
  • 4 Learning Objectives

About this Hands-on Lab

Strings are the primary way that we interact with non-numerical data in programming, and the `str` type in Python provides us with a lot of powerful methods to make working with string data easier. In this hands-on lab, we’ll be creating a script that can take a user-provided message and perform various actions on it before printing out those new results.

To feel comfortable completing this lab you’ll want to know how to do the following:

* Utilize methods on the `str` class. Watch the “Using String Methods” from the [Certified Entry-Level Python Programmer Certification][1] course.
* Working with list literals. Watch the “Lists” video from the [Certified Entry-Level Python Programmer Certification][1] course.
* Using List functions and methods. Watch the “List Functions and Methods” video from the [Certified Entry-Level Python Programmer Certification][1] course.

[1]: https://linuxacademy.com/cp/modules/view/id/413

Learning Objectives

Successfully complete this lab by achieving the following learning objectives:

Create the variations.py Script, Make It Executable with python3.7, and Accept User Input

For variations.py, we’re going to place it in our home directory (~) and we want to make sure that we can run it directly. To keep from being completely tied to the path of our python3.7 binary,
we want to set up our shebang properly.

Let’s create the file and set the shebang:

~/variations.py

#!/usr/bin/env python3.7

# Python implementation here

With the file created, we need to also make sure that it’s executable and we can do this using chmod:

$ chmod u+x ~/variations.py

Next, we’ll prompt the user for a message and store it off in a variable.

~/variations.py

#!/usr/bin/env python3.7

message = input("Enter a message: ")

Now if we run the script (./variations.py) it should prompt us for a message, and then exit without any errors.

Print the Lowercase, Uppercase, Title Case, and Capitalized Versions of the User’s Input

Now that we have the message variable, we’re going to print a few different things to the screen:

  • The lowercase version using str.lower
  • The uppercase version using str.upper
  • The title case version using str.title
  • The capitalized version using str.capitalize

Let’s use each of these methods combined with the print function:

~/variations.py

#!/usr/bin/env python3.7

message = input("Enter a message: ")

print("Lowercase:", message.lower())
print("Uppercase:", message.upper())
print("Capitalized:", message.capitalize())
print("Title Case:", message.title())

Now we can run the script to make sure that what we’ve written up to this point is working properly:

$ ./variations.py
Enter a message: This Is My Message
Lowercase: this is my message
Uppercase: THIS IS MY MESSAGE
Capitalized: This is my message
Title Case: This Is My Message
Separate the String and Present the Individual Words as a List

For the remaining requirements of our script, we need to work with the individual words. Because of this, we’re going to store the words off as a new variable, words. We can get the words by using the str.split method. After we’ve separated the message into words, let’s also print them out:

~/variations.py

#!/usr/bin/env python3.7

message = input("Enter a message: ")

print("Lowercase:", message.lower())
print("Uppercase:", message.upper())
print("Capitalized:", message.capitalize())
print("Title Case:", message.title())

words = message.split()
print("Words:", words)

Here’s the script running so far:

$ ./variations.py
Enter a message: This is a test Message!
Lowercase: this is a test message!
Uppercase: THIS IS A TEST MESSAGE!
Capitalized: This is a test message!
Title Case: This Is A Test Message!
Words: ['This', 'is', 'a','test','Message!']
Print the Alphabetic First and Last Words from the User’s Input

We’re going to sort the words in the words list alphabetically and save the new list to sorted_words by using the sorted built-in function. Lastly, we’ll print the alphabetic first and last words. Let’s do this by indexing to 0 and -1.

~/variations.py

#!/usr/bin/env python3.7

message = input("Enter a message: ")

print("Lowercase:", message.lower())
print("Uppercase:", message.upper())
print("Capitalized:", message.capitalize())
print("Title Case:", message.title())

words = message.split()
print("Words:", words)

sorted_words = sorted(words)
print("Alphabetic First Word:", sorted_words[0])
print("Alphabetic Last Word:", sorted_words[-1])

Here’s the final script running:

$ ./variations.py
Enter a message: This is a test message!
Lowercase: this is a test message!
Uppercase: THIS IS A TEST MESSAGE!
Capitalized: This is a test message!
Title Case: This Is A Test Message!
Words: ['This', 'is', 'a','test','message!']
Alphabetic First Word: This
Alphabetic Last Word: test

Additional Resources

Our script variations.py will allow us to provide a string and then it will present us with some permutations (all lowercase, all uppercase, etc), of that string. The script will also tell us the string's first and last words, when they are sorted alphabetically. We'll need to utilize numerous methods on the str class and some of the functions used to sort lists to make all of this this happen. Here's how we want the script to be used:

$ ./variations.py
Enter a message: This is my message
Lowercase: this is my message
Uppercase: THIS IS MY MESSAGE
Capitalized: This is my message
Title Case: This Is My Message
Words: ['This', 'is', 'my', 'message']
Alphabetic First Word: is
Alphabetic Last Word: This

Logging In

There are a couple of ways to get in and work with the code. One is to use the credentials provided in the hands-on lab overview page, log in with SSH, and use a text editor in the terminal.

The other is using VS Code in the browser. If you'd like to go this route, then you will need to navigate to the public IP address of the workstation server (provided in the hands-on lab overview page) on port 8080 (example: http://PUBLIC_IP:8080). Your password will be the same password that you'd use to connect over SSH.

Once we are in the server, create variations.py (with either VS Code or a command line text editor) and we can continue.

To feel comfortable completing this lab you'll want to know how to do the following:

What are Hands-on Labs

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