Input from user

There will be situations where your program has to interact with the user. For example, you would want to take input from the user and then print some results back. We can achieve this using the input() function and print function respectively.

Example:

def say_hi(name):
  print("Hello,", name + "!")
  
name = input("What's your name?\n")
say_hi(name)

Output:

What's your name?
Adriana
Hello, Adriana!

How It Works

The input() function takes a string as argument and saves it to a variable called name. Then it calls the function say_hi() with the name entered by the user as the argument. The function say_hi() prints the name argument concatenated with a Hello message.

Changing types

The input() function will always return a string. But many times we will want the user to enter other information, such as a number.

We can use functions like int() to transform a type into an integer and float() to transform a type into a float number.

Example:

def calculate_future(years, age):
  print("In", years, "you will be", age + years, "years old.")


age = input("What's your age?\n")
age_int = int(age)
calculate_future(10, age_int)

Output:

What's your age?
41
In 10 you will be 51 years old.

How It Works

The input() function takes a string as argument and saves it to a variable called age. Then it calls the function int() to convert the age entered by the user from string to integer and saves the value to a variable called age_int. The function calculate_future() is called with arguments 10 and the age entered by the user converted to integer, it then prints the age argument concatenated with a message saying how old the person will be in the number of years passed as argument to the function.