Flash cards
Review the key moves
What is the main idea behind Python User Input?
Lesson checks
Practice each idea before moving on
Short Mimo-style checks built from this lesson's code, terms, and sequence.
Which statement best captures the main point of this lesson?
Complete the missing token from the example code.
___("Enter your name:")Put the learning moves in the order that makes the concept easiest to apply.
User Input
Python allows for user input.
That means we are able to ask the user for input.
The following example asks for your name, and when you enter a name, it gets printed on the screen:
Ask for user input
print("Enter your name:")
name = input()
print(f"Hello {name}")Python stops executing when it comes to the input() function, and continues when the user has given some input.
Using prompt
In the example above, the user had to input their name on a new line. The Python input() function has a prompt parameter, which acts as a message you can put in front of the user input, on the same line:
Example
Add a message in front of the user input:
name = input("Enter your name:")
print(f"Hello {name}")Multiple Inputs
You can add as many inputs as you want, Python will stop executing at each of them, waiting for user input:
Multiple inputs
name = input("Enter your name:")
print(f"Hello {name}")
fav1 = input("What is your favorite animal:")
fav2 = input("What is your favorite color:")
fav3 = input("What is your favorite number:")
print(f"Do you want a {fav2} {fav1} with {fav3} legs?")Input Number
The input from the user is treated as a string. Even if, in the example above, you can input a number, the Python interpreter will still treat it as a string.
You can convert the input into a number with the float() function:
Example
To find the square root, the input has to be converted into a number:
x = input("Enter a number:")
#find the square root of the number:
y = math.sqrt(float(x))
print(f"The square root of {x} is {y}")Validate Input
It is a good practice to validate any input from the user. In the example above, an error will occur if the user inputs something other than a number.
To avoid getting an error, we can test the input, and if it is not a number, the user could get a message like "Wrong input, please try again", and allowed to make a new input:
Example
Keep asking until you get a number:
y = True
while y == True:
x = input("Enter a number:")
try:
x = float(x);
y = False
except:
print("Wrong input, please try again.")
print("Thank you!")