HOLIDAY SALE! Save 50% on Membership with code HOLIDAY50. Save 15% on Mentorship with code HOLIDAY15.

11) User Input and String Formatting Lesson

Python User Input

8 min to complete · By Martin Breuss

Contents

  1. Introduction
  2. Python Input from User
    1. Create the Script
    2. Execute the Script
    3. Communicate with the Script
  3. Python Get User Input Practice
  4. Python User Input Prompt Message
    1. Add Message Parameter
    2. Prompt Practice
  5. Build a Calculator with Input Prompts
    1. Input Function Returns a String
  6. Summary: Python User Input

Writing programs is much more fun when they're interactive. For example, it's hard to imagine a computer game that doesn't allow for some kind of input from the player. After all, playing gets interesting when you can actually do something.

Python Input from User

Python offers a convenient way to collect user input from the command line with the aptly named input().

Create the Script

Head over to your text editor, create a new file that you name collect.py, and add the following code:

user_input = input()

print(user_input)

Execute the Script

Save the file and execute it through your command line. The program will start running and then seemingly stop at a blank screen:

A terminal window with a secretly running Python script.

It looks like nothing is happening, but that's not true. You asked Python to open up a prompt for you to type in your input. Python is patiently waiting for you to do so.

Communicate with the Script

Give it a try. Once you type in any sort of input and press Enter, Python will print your input back to the command line:

Python program printing back a message to the terminal

After Python printed your message back to you, you might also notice that the terminal prompt changed back to normal. This means that your script has finished execution, and Python went on its well-deserved lunchtime break.

Nothing too world-displacing has happened here, you may think. All that Python did was copy the sentence that you typed. Not too impressive, Python. But that's just because printing a copy was the only thing that you asked Python to do with your input.

Python Get User Input Practice

  • Change the script to apply a string method to your input. For example, let Python repeat everything you say in ALL CAPS.
  • Then, make Python repeat only every second character from your input.

The subtle input() opens up the gates to your Python script so you can flood it with your personal input!

But while you, as the programmer, might remember what to type when Python goes blank and starts waiting for you, anyone else will probably think that your program died. And even if they trust your skills as a programmer, they will still not know what they are supposed to type in here! Luckily, input() takes an argument that can help with that.

Python User Input Prompt Message

You can add a string in between the parentheses of input(), and Python will display that message while waiting for your input.

Add Message Parameter

Improve your script by adding an explanatory sentence:

user_input = input("Enter something for Python to echo back: ")

print(user_input)

Save and run your script another time. Now Python will display the input prompt and make your program more understandable:

Python script displaying an input prompt

Whatever text you add as an argument to input() will be displayed when you run the program.

Prompt Practice

  • Add descriptive input prompts to the string-altering programs you wrote in the previous task.
  • Create a sarcastic program that asks a user for their honest opinion, then prints the same sentence back to them in aLtErNaTiNg CaPs.

Build a Calculator with Input Prompts

Next, think back to using Python as your calculator. You could simply type numbers and operators into your console, and Python evaluated the calculations for you. What if you wanted to create a calculator that displays nice input prompts:

number = input("Enter a number you want squared: ")

print(number ** 2)

Save and run the file, then give it a spin. Whoops! Not quite what you might have expected:

Error message displayed on a terminal

You managed to get Python quite confused, and it lets you know about that with a helpful error message:

TypeError: unsupported operand type(s) for ** or pow(): 'str' and 'int'

Input Function Returns a String

The reason you receive this error is that anything that comes in through input() will be a string. So even if you enter a number, such as 4, it will arrive in your program as the string "4".

In a future lesson, you'll revisit type conversion to make sure that your collected user input will have the right data type for your program to work with.

Summary: Python User Input

  • You can collect user input with input()
  • input() also takes a prompt string as an argument
  • Python will display the prompt string before the input prompt
  • Any user input collected with input() will be a string
  • The input collected from a user can be saved in a variable and used in your program
Previous Next → How to Convert Python Input from User