New MD5 hash after changing a TXT file in Python

Question

Good morning, So, I created a MD5 hash from a TXT file. After changing the file content inserting new values, I tried to create a MD5 hash again, but the value didn't change. What could I do?

My code:

from hashlib import md5

open_file = open('N0003966.290', 'r', encoding='ISO-8859-1')
file = open_file.read().lower().rstrip('\n\r ').strip('\n\r')

m = md5()
m.update(b'file')
print(m.hexdigest())

I need to follow some requirements to build this hash, such as:

The encoding rule must be 'ISO-8859-1'
All the characters must be lowercase
New line characters and carriage return characters must NOT be considered on hash building

Is that actually using the file object or the string 'file'? — doctorlove, Dec 15 '16 at 13:00

DevShark · Accepted Answer · 2016-12-15T13:07:34.830

2

You are calling update on the string 'file' rather than the content of the file. Do this instead:

from hashlib import md5

open_file = open('N0003966.290', 'r', encoding='ISO-8859-1')
file_content = open_file.read().lower().rstrip('\n\r ').strip('\n\r')

m = md5()
m.update(file_content.encode('ISO-8859-1'))
print(m.hexdigest())

Also note I replace your variable file by file_content (it is bad practice to override a built-in name).

edited Dec 15 '16 at 13:07

answered Dec 15 '16 at 13:04

DevShark

8,558
9
32
56

I tried this code also, but when I don't put a 'b' after the variable name, I got the error: TypeError: Unicode-objects must be encoded before hashing – Paulo Henrique Vasconcellos Dec 15 '16 at 13:06
Ah yes, you need to encode properly your string. Try with my edit. – DevShark Dec 15 '16 at 13:07
It's generating correctly a new hash after changing the txt file. The expect hash was not created, but I'l keep trying. Thank you @DevShark – Paulo Henrique Vasconcellos Dec 15 '16 at 13:17

score 1 · Answer 2 · edited May 23 '17 at 12:00

m.update(b'file')

This line is the problem. You're calling the function on the string 'file' represented as bytes (see this question, for example, for more on what that means), not on the data within the file.

If you replace it with

m.update(file)

you should get the results you want (although, as DevShark points out, you should also change the name of that variable to something that doesn't already have its own meaning).

score 0 · Answer 3 · answered Dec 15 '16 at 13:05

0

m.update(file.encode('ISO-8859-1'))

answered Dec 15 '16 at 13:05

gipsy

3,859
1
13
21

score 0 · Answer 4 · answered Dec 15 '16 at 13:11

This code works in python 2.7 too.

from hashlib import md5

open_file = open('a.txt', 'r')
file = open_file.read().lower().rstrip('\n\r ').strip('\n\r')

m = md5()
m.update(file)
print(m.hexdigest())

m.update(b'file') is the place where you got error replace it with m.update(file).

New MD5 hash after changing a TXT file in Python

4 Answers4