Compare Hash of two files in Python

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I need to compare the hash of the files a.txt and b.txt using a python3 native library.

I tried to do so:

import hashlib

file_0 = 'a.txt'
file_1 = 'b.txt'

hash_0 = hashlib.new('ripemd160')
hash_0.update(file_0)
hash_1 = hashlib.new('ripemd160')
hash_1.update(file_1)

assert hash_0 != hash_1, f'O arquivo: {file_0} é diferente do arquivo: {file_1} '

But the following error occurred:

Typeerror: Unicode-Objects must be encoded before hashing

Note: Before editing I made the error by two file_0 variables. In the project was correct.

python hash
  • 2

    Do you need to compare the contents of the files or their names only? The way you are doing you will only compare the names. The method update accepted only bytes-like as a parameter, then you will need to encode your string with the method encode.

  • I need to compare the contents of the file. I will continue searching and find how to compare the content. Thank you.

2 answers

7


First - you are comparing file names - the call to update in Hashlib classes does not open files alone - it expects objects of type "bytes" (and that is the reason for the error message, you are passing text) - but even if you put the prefix b' in these name strings, or use .encode() in the same, will continue to hash only the name of the files. (Another error: you used twice the same variable name - if you were opening the files, would be comparing the file "b. txt" with itself)

To see the hash of the contents of the files do:

import hashlib

file_0 = 'a.txt'
file_1 = 'b.txt'

hash_0 = hashlib.new('ripemd160')
hash_0.update(open(file_0, 'rb').read())

hash_1 = hashlib.new('ripemd160')
hash_1.update(open(file_1, 'rb').read())

if hash_0.digest() != hash_1.digest():
    print(f'O arquivo: {file_0} é diferente do arquivo: {file_1} ')

(you were also using the assert wrong way. Avoid using the assert in the same code - and reserve this command for testing. Although it seems a shortening of a if followed by a raise in some places, it is a test that is disabled depending on the parameters with which Python Runtime runs - so there is a lot of developer there assert in a production code that can get in trouble sooner or later, with a test that is not done, because of an apparently innocuous configuration changed elsewhere)

  • Forgive ignorance, but wouldn’t it be better to open files for reading rather than writing? Using rb instead of wb?

  • That should have been "Rb" - you’re wrong there - I’ll change.

5

To compare using hashlib can be done like this:

import hashlib

def open_txt(file):
    with open(file) as f:
        return "".join(f.read())

file_1 = 'a.txt'
file_2 = 'b.txt'
text_1 = open_txt(file_1)
text_2 = open_txt(file_2)

def compare(text_1, text_2):
    hash_1 = hashlib.md5()
    hash_1.update(text_1.encode('utf-8'))
    hash_1 = hash_1.hexdigest()

    hash_2 = hashlib.md5()
    hash_2.update(text_2.encode('utf-8'))
    hash_2 = hash_2.hexdigest()

    assert hash_1 == hash_2, f'O arquivo: {file_1} é diferente do arquivo: {file_2} '


compare(text_1, text_2)

But I find it more practical and fast to use filecmp that compares byte to byte.

import filecmp
filecmp.cmp('a.txt', 'b.txt')

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