Python Create SHA256 Hash of File[with Code Examples] - JSON Viewer

Python Create SHA256 Hash of File[with Code Examples]

Introduction to Python Create SHA256 Hash of File

Python is a well-liked programming language with a wide range of uses, including data processing, web development, and machine learning.

Making cryptographic hashes, which are used to protect the integrity and validity of data, is one of its powerful characteristics.

A message or file is the input for a cryptographic hash algorithm like SHA256, which yields a fixed-size output (hash value). The validity and integrity of the input data can be confirmed using this hash value.

Digital signatures, message authentication codes, and password storage are just a few examples of the many applications that make use of the widely used and regarded as safe SHA256 hash algorithm. We may check for file corruption or tampering by creating a SHA256 hash of the file.

The hashlib module of the robust and flexible programming language Python offers a quick and effective way to compute files’ SHA256 hash values. We can assure the validity and integrity of data in numerous applications by using Python to generate SHA256 hash values of files.

3 Steps to Python Create SHA256 Hash of File

Step 1: Import the hashlib module

Python has to import the hashlib module in order to generate a SHA256 hash of a file. Several cryptographic hash functions, including SHA256, are offered via the hashlib module. An illustration of how to import the hashlib module is shown below:

import hashlib

Step 2: Define the sha256_checksum function

def sha256_checksum(filename, block_size=65536):
    sha256 = hashlib.sha256()
    with open(filename, 'rb') as f:
        for block in iter(lambda:, b''):
    return sha256.hexdigest()

The SHA256 hash value of the file is returned as a hexadecimal string using the Python function sha256 checksum, which we define in this step.

The hashlib module, which offers a variety of cryptographic hash functions, including SHA256, is imported first. Then, we define the sha256_checksum function, which begins by creating a new SHA256 hash object using hashlib.sha256().

Next, we open the requested file in binary mode (‘rb’) using the open() function. Blocks of data of a defined size (block_size), which is set to a default value of 65536 bytes, are read from the file using the iter() method.

When called, an anonymous function created using the lambda function returns a block of data from the file.

Then, after iterating through each data block in the file using a for loop, we update the hash object for each block using the sha256.update() method. The sha256.hexdigest() method is used to obtain the final hash value as a hexadecimal string after all the blocks have been digested.

Step 3: Call the sha256_checksum function

filename = 'example.txt'
hash_value = sha256_checksum(filename)

We may use the sha256 checksum function after declaring it to compute the SHA256 hash of a file. To achieve this, we use the sha256 checksum function with the filename variable set to the name of the file whose SHA256 hash we wish to generate.

The file’s SHA256 hash value is returned by the sha256 checksum function as a hexadecimal string, which we save in the hash_value variable. The hash value is finally displayed on the console using the print() function.

These instructions will show you how to use Python to build a SHA256 hash of a file, which can be helpful for confirming the accuracy and legitimacy of your data.

Advantages of Creating SHA256

  • Security: The cryptographic hash function SHA256 is thought to be secure and challenging to crack. A file’s authenticity and integrity can be ensured by using SHA256 to construct a hash of the file.
  • Quick and effective: A quick and effective method for producing SHA256 hashes of files is to use the built-in hashlib module of Python.
  • Python is a cross-platform language, therefore the same code can be used to generate SHA256 hashes of files on several operating systems.
  • Flexibility: The hashlib module of Python offers a variety of hash functions, making it simple to change to a different algorithm when necessary.
  • Automation: Python’s ability to automate processes makes it simple to quickly and accurately generate SHA256 hashes of a large number of files.

Disadvantages of Creating SHA256

  • Limited error checking: If a file cannot be located or is not available, errors may arise when producing a hash of the file. It is the responsibility of the programmer to handle problems properly because the hashlib module for Python does not provide much error checking.
  • File size restriction: As the full file must be read into memory in order to create a hash, this method might not be appropriate for really big files that take up more memory than is available.
  • False sense of security: Despite the fact that SHA256 is regarded as secure, it’s vital to remember that a hash function just checks a file’s integrity and offers no encryption or security against unauthorised access.
  • Not foolproof: Although hashing a file can aid in spotting unintentional changes to the file, it is still feasible for an attacker to change the file and then produce a new hash that corresponds to the altered file.
  • Overhead: Generating a hash of a file adds another step to file processing, potentially lengthening processing time and consuming more resources.


In conclusion, Python provides a handy and easy-to-use mechanism to create SHA256 hash values for files using the hashlib module. You can compute a file’s SHA256 hash and utilise it for many things, such data integrity checks or authentication, by following the instructions in this guide.

The sha256 checksum function in this manual accepts a filename as input and generates a unique, fixed-length hash result for the file using the SHA256 hashing method.

In order to confirm the integrity of a file, the hash value is returned as a hexadecimal string that is simple to store, send, and compare to other hash values.

Overall, Python is a strong tool for working with data and maintaining its security and integrity because it comes with built-in support for cryptographic hash functions like SHA256.