Topic 15: File Handling in Python

 

File Handling in Python

File handling is one of the most important features in Python that allows users to store and access data from files permanently. Unlike variables that store data temporarily in memory, files store data permanently on disk.

Python provides built-in functions and methods to create, read, write, and delete files easily.

Why File Handling?

• To store data permanently for future use.

• To read or process existing data stored in text or binary files.

• To log information, such as errors or results, during program execution.

• To exchange data between programs.

File Operations in Python

Python provides four basic operations for handling files:

Operation	Description	Function
Open	Opens a file for reading/writing	open()
Read	Reads the content of a file	read(), readline(), readlines()
Write	Writes data to a file	write(), writelines()
Close	Closes an opened file	close()

Opening a File

file = open("example.txt", "r")

Modes of Opening a File

Mode	Description
'r'	Read mode (default)
'w'	Write mode (overwrites existing content)
'a'	Append mode (adds data to end of file)
'x'	Creates a new file and opens it for writing
'r+'	Read and write mode
'b'	Binary mode (used for images, PDFs, etc.)
't'	Text mode (default)

Example:

f = open("data.txt", "w")
f.write("Hello Python!")
f.close()

Reading from a File

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

Other Reading Methods

f.readline()      # Reads one line at a time
f.readlines()     # Reads all lines and returns a list

Example:

f = open("data.txt", "r")
for line in f:
    print(line.strip())
f.close()

Writing to a File

f = open("data.txt", "w")
f.write("This is a new line.")
f.close()

Appending new data:

f = open("data.txt", "a")
f.write("\nAppended line!")
f.close()

Using with Statement (Best Practice)

Python provides the with statement to automatically close the file after its use.

with open("data.txt", "r") as f:
    data = f.read()
    print(data)
# File is automatically closed

This is preferred because it avoids file corruption and resource leaks.

Working with Binary Files

Binary files store data in bytes (e.g., images, videos, audio).

with open("image.jpg", "rb") as f:
    data = f.read()
    print(type(data))  # <class 'bytes'>

To write binary data:

with open("copy.jpg", "wb") as f:
    f.write(data)

Checking File Existence

Use the os module:

import os

if os.path.exists("data.txt"):
    print("File exists.")
else:
    print("File not found.")

Deleting a File

import os
os.remove("data.txt")

Visual Flowchart of File Handling

     
File Handling

Conclusion

File handling in Python simplifies working with external files for permanent data storage.
By using proper file modes, error handling, and the with statement, you can create efficient and reliable programs that interact with files seamlessly.

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