How Struct.pack() Is Used to Create Packets?

How Struct Pack() Is Used To Create Packets

The struct method is used to create a packet of data in Python. This method is very similar to the transmission of electric signals. The signals are encoded first and then transmitted to another place. The Python language provides a different alternative to the struct method, i.e., byte() function, bytearray() function, and bitwise operators.

In this article, we will overview the concept of a struct module in Python and packet creation using struct.pack() method, and other related concepts.

What is Struct Method In Python?

The struct method is used to convert data into packets (as per the given format). The struct is a built-in method in Python. When we try to encode the data in the binary form, we need this struct method in Python. Again this data is decoded using the same method. The syntax of this struct method contains the information on how the data should be represented after decoding.

import struct
Sample = struct.pack( format_code, data)

The above code is a basic syntax of the struct method. To use the struct method in our code, first, we need to import the struct module. After importing the struct module, we need to use different functions according to our needs. For example, struct. pack(), struct.unpack(), struct.calcsize(), etc.

There are different format codes for different types of data. For example,

Sr NO.Data TypeFormat Code
2Unsigned Integer‘I’
4Unsigned Short‘H’
6Unsigned Long‘L’
9Signed Character‘b’
10Unsigned Character‘B’
Format code table

Using the combination of this format code, we can specify the format of the data. Let’s, implement some code to understand this struct method thoroughly.

Struct.pack() Function

In Python struct.pack() method converts data into tiny packets and represents that data in binary form. For this, we need to provide the data variables to the struct.pack() function. Remember to add data format code to get the results.

import struct 
sample = struct.pack('if', 4, 3.9)

Firsts, we are importing the struct method to use struct.pack() function in our code. Then, the struct.pack() function is used to encode the data in the form of packets using two types of arguments. here we have used ‘if’ as a data format that represents integer and float numbers. We simply printed the results in the last line.

Struct Pack Method
Struct Pack Method

The b prefix before the output conveys that these are binary numbers.

Struct.unpack() Method in Python

struct. unpack method in Python converts encoded data into its original form. The packets of binary numbers will be back into their original form. Let’s implement one example to understand the process.

import struct 
sample = struct.pack('if', 4, 3.9)
decode_sample = struct.unpack('if',sample)

Refer to line No.4 to understand the working of the struct.unpack() function in Python. The simple arguments, i.e., the data format and data, are provided for conversion.

Struct Unpack Method
Struct Unpack Method

, we can see the numbers are successfully converted into original formats.


The struct.calcsize() is used to know the size of the data present in the structure. It is similar to the len() function used to calculate the length of the arrays.

import struct 
sample = struct.pack('if', 4, 3.9)
length = struct.calcsize('if')

Line No. 4 executes struct.calcsize() function where format_code is used asana argument to get the length of the structure.

Struct Calcsize Method
Struct Calcsize Method

In the output, we can see the answer is 8. Here the data is an integer and float number, so their sum is 8.

Other Methods in Python to Create Packets

Bytes() function

The bytes() function in Python converts all the provided data into binary forms so they can be used as packets in further processes. This technique is very useful for converting data because of its simple syntax and one-line code.

bytes( list_of_data )
List_of_integers =[7,15,23,24,8]

The list of integers is provided for conversion into binary numbers. Let’s analyze the output.

Bytes Function
Bytes Function in Python

The numbers are successfully converted into binary numbers.

Bytearray() Function in Python

The Bytearray() function works similarly to the bytes() function the only difference is that we can change the data provided to the bytearray() function anytime. This is also one-line code with simple implementation.

List_of_integers =[7,15,23,24,8]
result = bytearray(List_of_integers)

The list is provided to the bytearray() function. Now, this will convert all the numbers into individual binary numbers. Let’s check the results.

Bytearray Function
Bytearray Function

The output image proves to us that we have used the bytearray() function for the conversion process.

Why do we need to Convert The Data into Binary Numbers/Packets?

We write programs for various purposes, and the need for data is everywhere. When we need to transmit this data from one place to another, it becomes easy to transmit it in packets. For example, in network communication systems, the data is always transmitted in the form of packets, so the encoding and decoding of the data becomes easy.

The conversion of data reduces the storage space of the dataset. Sometimes the dataset may contain a large amount of data, so to handle such datasets, we need to convert this dataset into binary form/ small packets. In this process, we always encode the data and then transmit it to another place so it is very secure as compared to other formats. This technique is very efficient in securing the data while transmitting.


In this article, you will learn about the struct method and its different functions used for the conversion of simple data into packets and binary numbers. There is a function called struct.pack() used for conversion, struct.unpack() used to decode. Other functions like bytes() and bytearray() are also used for the conversion. Along with this, the need for conversion is also explained in detail. Hope you will enjoy this article.


Do read the official documentation for more details.