Python File Handling: Syntax, Usage, and Examples
Python file handling allows reading, writing, appending, and managing files directly from code. It enables working with text files, binary files, and logging mechanisms for data storage, retrieval, and manipulation.
How to Use File Handling in Python
Python provides built-in functions to open, read, write, and close files. The open() function serves as the primary method for handling files in Python.
python
file = open("filename.txt", mode)
"filename.txt"refers to the file name and location.modedetermines how the file is accessed (read, write, append, etc.).
When to Use File Handling in Python
Storing and Retrieving Data
Applications frequently need to store user preferences, logs, or results in files. File handling simplifies data storage and retrieval.
python
with open("data.txt", "w") as file:
file.write("User preferences: Dark Mode Enabled")
Processing Large Files
Data analysis, logging, and automation tasks often require processing large text or CSV files.
python
with open("logfile.txt", "r") as file:
for line in file:
print(line.strip()) # Removes extra whitespace
Managing Configuration and Log Files
Applications generate logs to track system behavior and debug errors. File handlers in Python allow structured logging.
python
import logging
logging.basicConfig(filename="app.log", level=logging.INFO)
logging.info("Application started successfully")
Examples of File Handling in Python
Reading a File
Use the read() method to retrieve the entire file content.
python
with open("example.txt", "r") as file:
content = file.read()
print(content)
For line-by-line reading:
python
with open("example.txt", "r") as file:
for line in file:
print(line.strip())
Writing to a File
Use 'w' mode to write content.
python
with open("output.txt", "w") as file:
file.write("Hello, Python!")
Appending to a File
Appending adds content without overwriting existing data.
python
with open("output.txt", "a") as file:
file.write("\nNew line added.")
Handling File Exceptions
Catch errors to prevent crashes when a file doesn’t exist or access is restricted.
python
try:
with open("non_existent_file.txt", "r") as file:
print(file.read())
except FileNotFoundError:
print("File not found. Please check the file path.")
Learn More About File Handling in Python
File Handling Methods
Python provides built-in methods for efficient file operations.
read(size): Reads the specified number of bytes.readline(): Reads one line at a time.readlines(): Reads all lines and returns a list.write(string): Writes a string to the file.writelines(list): Writes multiple lines at once.seek(offset): Moves the cursor to a specific position.tell(): Returns the current cursor position.
Example of seek() and tell():
python
with open("example.txt", "r") as file:
file.seek(10) # Move to the 10th character
print(file.tell()) # Get current position
Using with to Handle Files
The with statement simplifies file handling by closing files automatically.
python
with open("example.txt", "r") as file:
print(file.read())
Python Logging File Handler
Python’s logging module provides a structured way to store logs.
python
import logging
logger = logging.getLogger("app_logger")
file_handler = logging.FileHandler("application.log")
formatter = logging.Formatter("%(asctime)s - %(levelname)s - %(message)s")
file_handler.setFormatter(formatter)
logger.addHandler(file_handler)
logger.setLevel(logging.INFO)
logger.info("Application started")
Working with Binary Files
Binary files store non-text content like images, audio, and videos. Use 'rb' and 'wb' modes to read and write them.
python
with open("image.png", "rb") as file:
image_data = file.read()
python
with open("copy.png", "wb") as file:
file.write(image_data)
Handling CSV Files
CSV files store structured data for easy processing. Python’s csv module simplifies reading and writing CSV files.
python
import csv
with open("data.csv", "w", newline="") as file:
writer = csv.writer(file)
writer.writerow(["Name", "Age"])
writer.writerow(["Alice", 25])
Reading a CSV file:
python
with open("data.csv", "r") as file:
reader = csv.reader(file)
for row in reader:
print(row)
Choosing the Right File Handling Mode
Using the correct file mode ensures smooth file operations.
'r'allows safe file reading.'w'creates or overwrites a file.'a'appends data without modifying existing content.'rb'and'wb'handle binary files.
Python file handling enables reading, writing, and managing files efficiently. Whether working with text, logs, binary data, or structured files like CSV, mastering file operations improves data management in applications. Understanding file handling methods, modes, and exception handling ensures reliable file interactions in Python programming.