Accept user input
Tip
See the Text and images tab for more details!
Programs become truly powerful when they can interact with the people using them. Python's built-in input() function lets you pause your program, wait for the user to type something, and capture that information.
Using input()
Think of the input() function as a question prompt. When Python hits this line, it waits until the user types their answer and presses the Enter key before continuing with the rest of the code.
To save their answer, you must "catch" it using a variable:
favorite_color = input("What is your favorite color? ")
print("Oh, I love", favorite_color, "too!")
In this code, favorite_color is a variable that catches the user's response. If the user types Blue and presses Enter, the output is:
What is your favorite color? Blue
Oh, I love Blue too!
You can try running this code yourself in an online python interpreter at https://aka.ms/python-coder.
Tip
Notice the blank space at the end of the prompt: "What is your favorite color? ". When accepting user input, add a space or new line before closing your quotes. If you don't, the user's typing will be glued directly to your text, looking messy like this:
What is your favorite color?Blue
A quick word about data types
Before you go further, it helps to know that every value in Python has a data type, which is a label that tells Python what kind of value it's working with. For example, some common data types are:
- String (
str): Text wrapped in quotes, like"Blue"or"25". Even a number becomes text when it's inside quotes. - Integer (
int): A whole number without quotes, like25or100. Python can do math with these.
Why does this matter? Python treats these two types very differently. You can add numbers together (25 + 1 equals 26), but you can't add a number to text ("25" + 1 causes an error).
The input is always text
An essential rule to remember is that the input() function always returns text, even if the user types a number. For example:
age = input("How old are you? ")
print("Next year you will be", age + 1)
If you run this code and type 25, you might expect it to print 26. Instead, Python crashes and displays an error message in your console:
TypeError: can only concatenate str (not "int") to str
Because the age is locked as text, you can't perform math operations on it just yet.
How to read this error
Errors are clues to what went wrong in the code. Let's break down these clues:
TypeError: You are trying to mix two data types that don't belong together.can only concatenate str (not "int") to str: "Concatenate" means to glue text together.
Python is saying: "You gave me the text "25", and asked me to glue the number 1 to it. I can glue text to text, but I don't know how to glue a math number to text!"
Because input() locks your user's response inside text quotes, Python sees your calculation as "25" + 1, which is an impossible math equation.