3.7 Python Input/Output (I/O)

In Python, Input/Output (I/O) refers to how a program receives data from the user and displays results back to the screen. The two primary built-in functions for this are input() and print().

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The input() Function

The input() function is used to receive data from the user via the keyboard.

Syntax

variable = input(prompt)

• prompt — an optional string displayed to the user before they type.
• The function always returns a string, regardless of what the user types.

Example

name = input("Enter your name: ")
print("Hello,", name)

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Type Casting Input

Since input() always returns a string, you must convert (cast) it to the appropriate data type before performing calculations.

Example

num1 = int(input("Enter first number: "))
num2 = int(input("Enter second number: "))
print("Sum =", num1 + num2)

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The print() Function

The print() function is used to display output on the screen.

Syntax

print(object1, object2, ..., sep=' ', end='\n')

Basic Examples

print("Hello, World!")        # Output: Hello, World!
print("Age:", 17)             # Output: Age: 17
print(10 + 5)                 # Output: 15

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Parameters of print()

sep Parameter

Specifies the separator between multiple objects. Default is a single space ' '.

print("Python", "is", "fun", sep="-")
# Output: Python-is-fun

print(1, 2, 3, sep=", ")
# Output: 1, 2, 3

end Parameter

Specifies what is printed at the end of the output. Default is a newline '\n'.

print("Hello", end=" ")
print("World")
# Output: Hello World  (on the same line)

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Escape Sequences

Escape sequences are special characters that begin with a backslash (\) and are used to format output.

Example

print("Name:\tAli")
# Output: Name:    Ali

print("Line 1\nLine 2")
# Output:
# Line 1
# Line 2

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String Formatting with print()

You can combine variables and strings in output using:

Comma Separation

name = "Sara"
age = 16
print("Name:", name, "Age:", age)
# Output: Name: Sara Age: 16

f-Strings (Formatted String Literals)

name = "Sara"
age = 16
print(f"Name: {name}, Age: {age}")
# Output: Name: Sara, Age: 16

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Worked Example: Simple Calculator

num1 = float(input("Enter first number: "))
num2 = float(input("Enter second number: "))
sum = num1 + num2
print(f"The sum of {num1} and {num2} is {sum}")

Sample Run:

Enter first number: 5.5
Enter second number: 4.5
The sum of 5.5 and 4.5 is 10.0

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