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📂 Python File Handling – Read, Write, and Manage Files

🧲 Introduction – Why File Handling Matters in Python?

File handling is an essential skill in Python for creating, reading, writing, updating, and deleting files. Whether you’re working on configuration files, logs, or data processing tasks, file I/O (Input/Output) operations are at the core of real-world Python applications.

🎯 In this guide, you’ll learn:

How to read, write, delete, and rename files
Methods for managing files and directories using the os and os.path modules
Common file-handling methods with real-life examples

📌 Topics Covered

🧩 Topic	📘 Description
Python File Handling Explained	Opening, reading, writing, and closing files
Python Read Files	How to read files line-by-line or in chunks
Python Write/Create Files	Write text or data to new or existing files
Python Delete Files	Remove unwanted files safely
Python Renaming and Deleting Files	Rename and delete using the `os` module
Python File Methods	Built-in file object methods like `read()`, `write()`, `close()`
Python OS File/Directory Methods	Manage files/folders with `os` functions
Python OS Path Methods	Use `os.path` to validate, join, and navigate paths

🗂️ Python File Handling Explained

To handle files, you typically use the built-in open() function.

file = open("example.txt", "r")
print(file.read())
file.close()

✅ Modes:

'r' – Read (default)
'w' – Write (overwrite)
'a' – Append
'x' – Create
'b' – Binary mode
't' – Text mode (default)

Use a with block to auto-close files:

with open("example.txt", "r") as file:
    content = file.read()

📖 Python Read Files

🔹 Read Entire File

with open("sample.txt", "r") as f:
    print(f.read())

🔹 Read Line-by-Line

with open("sample.txt", "r") as f:
    for line in f:
        print(line)

🔹 Read Specific Lines

with open("sample.txt", "r") as f:
    print(f.readline())

✍️ Python Write/Create Files

🔹 Overwrite Existing or Create New File

with open("output.txt", "w") as f:
    f.write("This will overwrite the file.")

🔹 Append to a File

with open("output.txt", "a") as f:
    f.write("\nAppending new line.")

❌ Python Delete Files

import os

if os.path.exists("output.txt"):
    os.remove("output.txt")
else:
    print("File does not exist.")

📝 Python Renaming and Deleting Files

🔹 Rename a File

os.rename("old.txt", "new.txt")

🔹 Delete a Directory

os.rmdir("myfolder")

⚠️ Only works if the directory is empty.

🧰 Python File Methods

Method	Description
`read()`	Reads the entire file
`readline()`	Reads one line
`readlines()`	Returns a list of lines
`write()`	Writes string to file
`writelines()`	Writes list of strings
`close()`	Closes the file

📁 Python OS File/Directory Methods

Method	Description
`os.remove()`	Delete a file
`os.rename()`	Rename a file or directory
`os.rmdir()`	Remove an empty directory
`os.mkdir()`	Create a new directory
`os.listdir()`	List contents of a directory
`os.getcwd()`	Get the current working directory
`os.chdir(path)`	Change working directory

📂 Python OS Path Methods

import os

print(os.path.exists("example.txt"))     # Check if file exists
print(os.path.isfile("example.txt"))     # Check if it's a file
print(os.path.isdir("myfolder"))         # Check if it's a directory
print(os.path.join("folder", "file.txt")) # Join paths

🧪 Python File Handling Exercises

✅ 1. Write and read from a file

with open("test.txt", "w") as f:
    f.write("Python file handling!")
with open("test.txt", "r") as f:
    print(f.read())

✅ 2. Append and print all lines

with open("test.txt", "a") as f:
    f.write("\nAppended line.")
with open("test.txt") as f:
    for line in f:
        print(line.strip())

✅ 3. Rename and delete file

os.rename("test.txt", "new_test.txt")
os.remove("new_test.txt")

📌 Summary – Recap & Next Steps

Python’s file handling capabilities allow you to interact with the filesystem easily. From basic reading and writing to advanced OS-level file operations, mastering these tools empowers you to automate real-world tasks.

🔍 Key Takeaways:

Use open() with modes (r, w, a, x) to manage files.
File objects offer methods like read(), write(), close().
Use os and os.path modules for advanced file/directory management.
Always close files, or use with statements for safety.

⚙️ Real-World Relevance:
Used in configuration management, logging, data pipelines, automation scripts, and backups.

❓ FAQ – Python File Handling

❓ What does the with open() syntax do?
✅ It automatically handles opening and closing files, even if an error occurs.

❓ How do I check if a file exists?

import os
os.path.exists("filename.txt")

❓ What’s the difference between write() and writelines()?
✅ write() adds a string; writelines() takes a list of strings.

❓ Can I delete a folder with files inside using os.rmdir()?
❌ No. Use shutil.rmtree() instead for non-empty folders.

❓ How to join paths safely across platforms?
✅ Use os.path.join():

os.path.join("folder", "file.txt")

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