Python: How to calculate the MD5 Hash of a File

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# Python: How to calculate the MD5 Hash of a File

To calculate the MD5 hash of a file in Python:

Use the with open() statement to open the file in rb (read bytes) mode.
Use the file.read() method to read the file's contents.
Use the hashlib.md5().hexdigest() method to get the MD5 hash of the file.

Suppose we have the following example.txt file.

example.txt

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bobby
hadz
com

Here is the related Python script.

main.py

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import hashlib

file_name = 'example.txt'

with open(file_name, 'rb') as file_obj:
    file_contents = file_obj.read()

    md5_hash = hashlib.md5(file_contents).hexdigest()

    # 👇️ cfd2db7dd4ffe42ce26e0b57e7e8b342
    print(md5_hash)

python calculate md5 hash of file

The code for this article is available on GitHub

We used the with open() statement to open the file in rb (read binary) mode.

The with open() statement takes care of closing the file after we're done, even if an exception occurs.

The next step is to read the contents of the file into a string with file.read().

The hash.hexdigest() method returns the digest as a string.

If you need to take the file path from user input, check out this article.

# Using the `open()` function directly

If you use the older syntax that uses the open() function directly, make sure to manually close the file.

main.py

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import hashlib

file_name = 'example.txt'

file_obj = open(file_name, 'rb')

file_contents = file_obj.read()

md5_hash = hashlib.md5(file_contents).hexdigest()

# 👇️ cfd2db7dd4ffe42ce26e0b57e7e8b342
print(md5_hash)

file_obj.close()

The code for this article is available on GitHub

This helps you avoid memory leaks in your Python program.

# Verifying the returned MD5 hash

If you need to compare the returned MD5 hash against a string, use the equality operator.

main.py

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import hashlib

file_name = 'example.txt'

md5_hash_original = 'cfd2db7dd4ffe42ce26e0b57e7e8b342'

with open(file_name, 'rb') as file_obj:
    file_contents = file_obj.read()

    md5_hash_new = hashlib.md5(file_contents).hexdigest()

    print(md5_hash_new)

if md5_hash_original == md5_hash_new:
    print('MD5 hash verified')
else:
    print('MD5 hash verification failed')

verify returned md5 hash

The code for this article is available on GitHub

If the returned MD5 hash matches, the if block runs, otherwise, the else block runs.

# Calculate the MD5 Hash of a large File in chunks

If you're working with a relatively large file, you might not want to read its entire contents in memory.

In this case, you can use file.read() with a specific number of bytes to read the file in chunks.

Suppose we have the same example.txt file.

example.txt

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bobby
hadz
com

Here is the related Python code.

main.py

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import hashlib

file_name = 'example.txt'

with open(file_name, 'rb') as file_obj:
    md5_hash = hashlib.md5()

    while chunk := file_obj.read(4096):
        md5_hash.update(chunk)

# 👇️ as a string
print(md5_hash.hexdigest())

# 👇️ or as bytes
print(md5_hash.digest())

The code for this article is available on GitHub

Running the code sample produces the following output.

shell

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b'\xcf\xd2\xdb}\xd4\xff\xe4,\xe2n\x0bW\xe7\xe8\xb3B'

cfd2db7dd4ffe42ce26e0b57e7e8b342

calculate md5 hash of large file in chunks

We opened the file in rb (read binary) mode and used a while loop to iterate over the file's contents in chunks of 4096 bytes.

On each iteration, we update the hash with the current chunk.

You can use the hash.hexdigest() method to print the hash as a string or the hash.digest() method to print it as bytes.

If you have to do this often, define a reusable function.

main.py

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import hashlib


def get_md5_hash(file_path, block_size=4096):

    with open(file_path, 'rb') as file_obj:
        md5_hash = hashlib.md5()

        while chunk := file_obj.read(block_size):
            md5_hash.update(chunk)

    return md5_hash.hexdigest()


file_name = 'example.txt'

print(get_md5_hash(file_name))

define reusable function

The code for this article is available on GitHub

The function takes the file path and the block size as arguments and returns the MD5 hash of the file.

You can achieve the same result by using a for loop.

main.py

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import hashlib


def get_md5_hash(file_path, block_size=4096):

    with open(file_path, 'rb') as file_obj:
        md5_hash = hashlib.md5()

        for chunk in iter(
            lambda: file_obj.read(block_size), b''
        ):
            md5_hash.update(chunk)

    return md5_hash.hexdigest()


file_name = 'example.txt'

print(get_md5_hash(file_name))

achieve same result by using a for loop

The code for this article is available on GitHub

# Using the `hashlib.file_digest()` method (Python3.11+)

If your Python version is greater than 3.11, you can also use the efficient hashlib.file_digest method.

You can check your Python version with the python --version command.

shell

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python --version

# or python3
python3 --version

If your Python version is greater than 3.11, try using the hashlib.file_digest() method.

main.py

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import hashlib

file_name = 'example.txt'

with open(file_name, 'rb') as file_obj:
    digest = hashlib.file_digest(file_obj, 'md5')

print(digest.hexdigest())

using hashlib file digest method

The code for this article is available on GitHub

The hashlib.file_digest() method takes a file object and a digest as parameters and returns a digest object that has been updated with the contents of the file object.

The digest argument must either be a hash algorithm name as a string, a hash constructor or a callable that returns a hash object.

Note that the hashlib.file_digest() method is introduced in Python v3.11.

# Calculate the MD5 Hash of a File using `mmap`

You can slo use the mmap() class from the mmap module to calculate the hash of a file.

main.py

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from mmap import mmap, ACCESS_READ
from hashlib import md5

file_name = 'example.txt'


with open(file_name, 'rb') as file, mmap(
        file.fileno(),
        0,
        access=ACCESS_READ) as file:
    print(md5(file).hexdigest())

calculate md5 hash of file using mmap

The code for this article is available on GitHub

The mmap() class maps N bytes from the file and returns a mmap object.

We set the length argument to 0, so the max length of the map will be the current size of the file when mmap is called.

# Using a `pathlib.Path` object instead

The pathlib.Path class is used to create a PosixPath or a WindowsPath object depending on your operating system.

If your code should be able to run on both Windows and Unix, use the pathlib.Path class to construct a PurePath.

main.py

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import pathlib
import hashlib

file_name = 'example.txt'

path_obj = pathlib.Path(file_name)


md5_hash = hashlib.md5(path_obj.read_bytes()).hexdigest()
print(md5_hash)

use pathlib path to get md5 hash

# Additional Resources

You can learn more about the related topics by checking out the following tutorials:

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Python: How to calculate the MD5 Hash of a File

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