Computer Science
Grade 8
20 min
File I/O Operations
File I/O Operations
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1
Introduction & Learning Objectives
Learning Objectives
Explain the purpose of File I/O (Input/Output) in programming.
Use the `with open()` statement to safely open and close files.
Write a Python script to create a new text file and write data to it.
Read data from an existing text file and display it.
Append new data to the end of an existing file without deleting its contents.
Iterate through a file line by line to process its data.
Ever wondered how a video game saves your high score or how an app remembers your settings even after you close it? 🤔 The secret is writing to files!
This lesson introduces File I/O (Input/Output), a powerful way for your Python programs to interact with files on your computer. You will learn how to save data permanently, read it back later, and update it, making your program...
2
Key Concepts & Vocabulary
TermDefinitionExample
File I/OStands for File Input/Output. It's the process of a program reading data from a file (Input) or writing data to a file (Output).Your Python script reading a list of usernames from `users.txt` is Input. Your script saving a new high score to `scores.txt` is Output.
File PathThe location of a file on your computer, like a street address for a house. A simple filename refers to a file in the same directory as your Python script.`'my_notes.txt'` (relative path) or `'C:/Users/Student/Documents/my_notes.txt'` (absolute path).
File HandleA variable that represents the connection between your program and a file on the disk. You use this handle to perform read or write operations.In `with open('data.txt') as f:`, the variable `f` is...
3
Core Syntax & Patterns
The 'with open()' Statement
with open('filename.txt', 'mode') as file_variable:
This is the safest and most common way to work with files. It automatically closes the file for you when you're done, even if errors occur. The 'mode' is a letter like 'r', 'w', or 'a'.
Writing to a File
file_variable.write('some string data\n')
Inside a `with open()` block (using 'w' or 'a' mode), use the `.write()` method on the file handle to save a string to the file. Remember to add `\n` to move to the next line.
Reading from a File
for line in file_variable:
Inside a `with open()` block (using 'r' mode), you can use a `for` loop to read the file one line at a time. Each...
4 more steps in this tutorial
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Challenging
A file `data.txt` contains:
Apple
Banana
Cherry
What will be the final content of `data.txt` after this code runs?
`with open('data.txt', 'r') as f:
lines = f.readlines()
with open('data.txt', 'w') as f:
f.write(lines[2])
f.write(lines[0])`
A.Cherry
Apple
B.Banana
C.Apple
Banana
Cherry
Cherry
Apple
D.The code will result in an error.
Challenging
A program uses `f = open('game.log', 'w')` but crashes before `f.close()` is called. What is a likely problem, and how does `with open()` prevent it?
A.The file is deleted; `with open()` prevents deletion on crash.
B.The file becomes read-only; `with open()` ensures it stays writeable.
C.The file may be empty or incomplete because data wasn't saved from memory; `with open()` automatically closes and saves the file even if a crash occurs within its block.
D.The computer's memory will leak; `with open()` frees the memory faster.
Challenging
Using the concepts from the tutorial, how would you read `shopping_list.txt` (containing 'Milk\nBread\nEggs\n') and print a numbered list like "1. Milk", "2. Bread", etc.?
A.with open('shopping_list.txt', 'w') as f:
print(f.read_numbered())
B.count = 1
with open('shopping_list.txt', 'r') as f:
print(f'{count}. {f.read()}')
C.with open('shopping_list.txt', 'r') as f:
for item in f:
print(f'1. {item.strip()}')
D.count = 1
with open('shopping_list.txt', 'r') as f:
for item in f:
print(f'{count}. {item.strip()}')
count += 1
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