What is the use of the "struct" module in Python?

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Jayant Kumar · Accepted Answer

Table of Contants
Introduction
The struct module in Python is a powerful tool for working with binary data, allowing you to convert between Python values and C-style data structures. It is commonly used to handle raw binary data, especially when dealing with file formats or network protocols that require packing and unpacking data into a specific binary format.
In this article, we’ll explore the purpose of the struct module, its key functionalities, and how to use it for manipulating binary data.
What Is the struct Module?
The struct module is used to interpret strings as packed binary data and convert between Python values (like integers or floats) and bytes. It can handle the serialization (packing) and deserialization (unpacking) of data into formats compatible with C structs, which are frequently used in low-level programming.
Key Functions in the struct Module:

**pack()**: Converts Python values into a binary data format.
**unpack()**: Converts binary data into Python values.
**calcsize()**: Returns the size (in bytes) of a given format.

These functions rely on format strings, which define the structure of the binary data by specifying the types of the values being packed or unpacked.
Example Format Codes:

'i': Integer (4 bytes)
'f': Float (4 bytes)
'd': Double (8 bytes)
's': String
'?': Boolean (1 byte)

How to Use the struct Module
The struct module is primarily used for converting Python data types into binary data and vice versa. This is useful when reading or writing binary files, communicating over network protocols, or interacting with hardware at a low level.
Packing Data with struct.pack()
To convert Python values into a binary format, use the pack() function. The format string specifies the structure of the binary data, and the function returns a bytes object.
import struct

# Pack two integers and a float into binary format
binary_data = struct.pack('iif', 1, 2, 3.5)

print(binary_data)

In this example, the format string 'iif' indicates two integers (i) followed by a float (f). The resulting binary_data is a byte sequence that can be saved to a file or transmitted over a network.
Unpacking Data with struct.unpack()
To convert binary data back into Python values, use the unpack() function. It extracts the data according to the format string, returning a tuple of values.
# Unpack binary data into Python values
unpacked_data = struct.unpack('iif', binary_data)

print(unpacked_data)  # Output: (1, 2, 3.5)

The format string 'iif' tells Python how to interpret the binary data, which in this case unpacks into two integers and a float.
Practical Use Cases of the struct Module
Reading Binary Data from Files
Many binary file formats, such as image or audio files, use specific structures that can be parsed using the struct module. For example, you can read the header of a .wav audio file by unpacking its data structure.
# Open a binary file and read its first 12 bytes (header)
with open('audio.wav', 'rb') as file:
    header = file.read(12)

# Unpack the header (using a hypothetical format)
file_format = struct.unpack('4sI4s', header)

print(file_format)

Working with Network Protocols
The struct module is also useful when communicating over networks, where data must be sent in a specific binary format. For example, you can pack data before sending it across a socket.
import socket

# Pack data to be sent over a network
packed_data = struct.pack('!I', 12345)  # '!I' means network byte order, 4-byte integer

# Send data over a socket
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect(('localhost', 8000))
sock.sendall(packed_data)

In this case, the ! in the format string specifies network byte order, which ensures compatibility across different machines.
Handling Sensor Data
When interacting with hardware or sensors, data often comes in a packed binary format. Using the struct module, you can unpack this data into Python-readable values.
# Example of unpacking sensor data (2 floats)
sensor_data = b'\x9a\x99\x99\x3f\xcd\xcc\xcc\x3f'  # Binary data from sensor
unpacked_values = struct.unpack('ff', sensor_data)

print(unpacked_values)  # Output: (1.2, 1.3)

Conclusion
The Python struct module is a valuable tool for converting between Python data types and binary formats, making it essential for tasks like reading binary files, working with network protocols, and interacting with hardware. By mastering this module, you can efficiently handle packed data in various contexts.
Whether you are working with file formats, sensor data, or networking, the struct module offers a straightforward solution for packing and unpacking binary data.

What is the use of the "struct" module in Python?

Table of Contants

Introduction

What Is the `struct` Module?

Key Functions in the `struct` Module:

Example Format Codes:

How to Use the `struct` Module

Packing Data with `struct.pack()`

Unpacking Data with `struct.unpack()`

Practical Use Cases of the `struct` Module

Reading Binary Data from Files

Working with Network Protocols

Handling Sensor Data

Conclusion

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