Python - File Handling

File Handling in Python

File Handling in Python is a powerful feature that allows you to create, read, update, and delete files. Python has built-in file manipulation functions and methods. Makes it easy to work with text and binary files.

Python File Handling

Python supports file handling and allows users to manipulate files, such as reading and writing files. Along with many other file management options, the concept of file handling has spread to many other languages, but implementation can be complicated or lengthy. Like many other concepts in Python, this one is also simple and short.

Python treats files differently as text or binary and this is important. Each line of code includes a sequence of characters, and they form a text file. Each line of a file is terminated with a special character, called the EOL or End of Line characters like comma {,} or newline character.

File Mode

Python supports various file modes:

• r: Read mode, opens a file for reading.
• w: Write mode, creates a new file or truncates an existing one.
• x: Exclusive creation, fails if the file already exists.
• a: Append mode, write data to the end of the file.
• b: Binary mode. Use with other modes for binary files.
• t: Text mode (default). Use with other modes for text files.
• +: Read and write mode. Combines with r, w, or a.

Opening and Closing a File

Opening and closing a file is important because to read and write to a file, you first need to open it. After the process of reading or writing is finished, you should close the file.

Use the open() function to open a file and close() to release resources.

# Open a file in read mode
file = open("example.txt", "r")

# Perform operations
content = file.read()
print(content)

# Close the file
file.close()

Alternatively, you can use the 'with' statement to manage files. It automatically closes the file after the block of code.

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

Reading a File

In Python, reading from a file refers to retrieving the contents of a file stored on a disk and retrieving that data for use in your program. The following steps involve reading from files:

• Open the File: You use the open() function to specify the file name and the mode (e.g., read mode 'r').
• Read the Contents: You can read the entire file at once, read it line by line, or read specific portions, depending on your needs.
• Process the Data: Once you have the data, you can manipulate it, display it, or use it in calculations.
• Close the File: It’s essential to close the file after reading to free up system resources. However, using a with statement automatically closes the file for you.

The following are the useful methods when we read a file:

• read(): Reads the entire file as a string.
• deadline(): Reads one line at a time.
• readlines(): Returns a list of all lines.

Example

Let's see an example of how reading a file works:

with open("example.txt", "r") as file:
    # Read the entire file
    print(file.read())

    # Read line by line
    file.seek(0)  # Reset pointer to the beginning
    print(file.readline())
    print(file.readline())

    # Read all lines into a list
    file.seek(0)
    print(file.readlines())

Writing to a File

In Python, file writing refers to the process of creating or modifying a file by appending it to data. This can include creating a new file, overwriting an existing file, or appending data to the end of an existing file. The following steps involve Writing a File:

• Open the File: You use the open() function to specify the file name and the mode (e.g., write mode 'w' or append mode 'a').
• Write the Data: You can write a string, a list of strings, or formatted data to the file.
• Close the File: It’s important to close the file after writing to ensure that all data is saved properly and system resources are freed. Using a with statement automatically handles closing the file for you.

The following are the useful methods for writing to a file:

• write(): Writes a string to the file.
• writelines(): Writes a list of strings.

Example

Let's see an example, of how to write to a file:

# Writing to a file
with open("example.txt", "w") as file:
    file.write("This is a new line.\n")
    file.write("This is another line.\n")

# Appending to a file
with open("example.txt", "a") as file:
    file.write("Appending a line.\n")

Working with Binary Files

The binary files store data in binary format, such as image, video, and audio.

Example

Let's see an example of how you can work with binary files:

# Reading a binary file
with open("image.png", "rb") as file:
    binary_data = file.read()

# Writing to a binary file
with open("copy_image.png", "wb") as file:
    file.write(binary_data)

Checking File Existence

You can use the 'os' module to check if a file exists:

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