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2.2. I/O Operations

In this section, we'll be looking at how we can take input from user and produce an output.

Formatting output

For a recap, in the 1.3. Hello World, we learnt about the print() function which allows us to output messages.

The print() function provides some extra functionality that allows us to format our output.

Multiple messages

We can pass multiple messages to this function that will be separated by space when outputing:

print('Hello', 'World!')

Hello World!

This is particulary useful when outputting values of a variable:

age = 20
print('The age of this user is', age, 'years.')

The age of this user is 20 years.

By default, the passed messages are joined with space as a separator. If you want to change the separator, we can do that by passing a sep parameter:

print('apple', 'banana', 'peach', sep=', ')

apple, banana, peach

Newlines and ending

In order to move to a newline when outputing messages, a special "escape character" is used. This escape character is \n.

Escape Characters

Other than new line escape characters, there are various other escape characters for various purposes which will be discussed later in this guide.

For example:

print('Line 1\nLine2\nLine3')

Line 1
Line 2
Line 3

Note that when we call a print statement. The output message automatically appended with a new line character. Hence, the following code produces the same output as above:

print('Line 1')
print('Line 2')
print('Line 3')

Line 1
Line 2
Line 3

If we don't want the end of each output to be new line, we can pass another character to end argument. By default, end is set to \n

print('Line 1', end='.')
print('Line 2', end='.')
print('Line 3', end='.')

Line 1.Line 2.Line 3.

Taking user input

A program is incomplete without user input. Every program requires an input in some way or another.

The most basic way of taking user input is by using the input() function:

name = input('Enter your name: ') # (1)!
print('Hello,', name)
  1. If we don't pass any message to input() function, no prompt is shown in the terminal.
Enter your name: John # (1)!
Hello, John
  1. "John" is the given user input.

Converting input type

The input() function returns the input as a string (str data type). In cases where you are expecting a different type, you must convert the string to that type explicitly.

For example, the following program takes two numbers and adds them:

n1 = input('Enter number 1: ')
n2 = input('Enter number 2: ')

n1 = int(n1)  # (1)!
n2 = int(n2)  # (2)!

print(n1 + n2)
  1. n1 converted to int type.
  2. n2 converted to int type.
Enter number 1: 20
Enter number 2: 50
70

For more information on data type conversion, take a look at the 2.1. Variables and Data Types: Converting data types topic.