2.5.1 Implementing input and output

Keyboard Input

Purpose: Accept data entered by the user.

When used: To gather user input during program execution.

Python example:


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

Screen Output

Purpose: Display information to the user.

When used: To show results, messages, or errors.

Python example:


total = 25
print("The total is:", total)

Text File Input and Output

Purpose: Store and retrieve data permanently.

When used: For saving results or reading stored data.

Opening a File for Reading

Python example:


file = open("data.txt", "r")
content = file.read()
file.close()

print(content)

Opening a File for Writing

Python example:


file = open("output.txt", "w")
file.write("Hello, file!")
file.close()

Writing Multiple Lines to a File

Python example:


file = open("numbers.txt", "w")

for i in range(1, 6):
    file.write(str(i) + "\n")

file.close()

Interpreting I/O Code

Interpreting code means understanding how data flows into and out of a program.

Example:


age = int(input("Enter your age: "))
print(age + 1)

This code reads a value from the keyboard, converts it, and outputs a result.

Creating I/O Code

Python example:


price = float(input("Enter price: "))
quantity = int(input("Enter quantity: "))

total = price * quantity
print("Total cost:", total)

Debugging I/O Code

Incorrect code:


number = input("Enter a number: ")
print(number + 5)

Problem: Input is a string, not a number.

Corrected code:


number = int(input("Enter a number: "))
print(number + 5)