Python allows you to read, write, and manipulate files, as well as interact with your operating system.
1) Why File Handling and OS Interaction?
File handling is essential to save and retrieve data persistently. OS interaction allows Python programs to communicate with the system for tasks like checking directories, listing files, or running commands.
2) File Handling Basics
Python provides the built-in open() function to work with files.
# Open a file in write mode
file = open("example.txt", "w")
file.write("Hello, World!\n")
file.write("Python is amazing!")
file.close()
# Open a file in read mode
file = open("example.txt", "r")
content = file.read()
print(content)
file.close()
Modes:
"r"– Read (default)"w"– Write (overwrite)"a"– Append"r+"– Read & Write"b"– Binary mode (e.g.,"rb")
3) Using with Statement
Automatically closes the file after the block, reducing errors.
with open("example.txt", "r") as file:
content = file.read()
print(content)
# File is automatically closed here
4) Reading Lines from a File
with open("example.txt", "r") as file:
# Read line by line
for line in file:
print(line.strip())
# Read all lines into a list
file.seek(0)
lines = file.readlines()
print(lines)
5) Writing Multiple Lines
lines = ["Line 1\n", "Line 2\n", "Line 3\n"]
with open("example.txt", "w") as file:
file.writelines(lines)
6) Interacting with the Operating System
Python’s os module allows you to work with directories and files.
import os
# Current working directory
print(os.getcwd())
# List files and directories
print(os.listdir())
# Create a directory
os.mkdir("new_folder")
# Rename a file
os.rename("example.txt", "example_renamed.txt")
# Delete a file
os.remove("example_renamed.txt")
# Remove a directory
os.rmdir("new_folder")
7) Common Mistakes
- Forgetting to close files (use
withto avoid this) - Opening a non-existent file in read mode →
FileNotFoundError - Trying to remove non-empty directories →
OSError - Confusing relative and absolute paths
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