Is it an MD5 digest in this Python script?

Question

I am trying to understand this simple hashlib code in Python that has been given to me the other day on Stackoverflow:

import hashlib
m = hashlib.md5()
m.update("Nobody inspects")
m.update(" the spammish repetition here")
m.digest()
'\xbbd\x9c\x83\xdd\x1e\xa5\xc9\xd9\xde\xc9\xa1\x8d\xf0\xff\xe9'
m.digest_size
16
m.block_size
64
print m

I thought that print m would show me the MD5 digest of the phrase: "Nobody inspects the spammish repetition here", but as a result I got this line on my local host:

<md5 HASH object @ 01806220>

Strange, when I refreshed the page, I got another line:

<md5 HASH object @ 018062E0>

and every time when I refresh it, I get another value:

md5 HASH object @ 017F8AE0

md5 HASH object @ 01806220

md5 HASH object @ 01806360

md5 HASH object @ 01806400

md5 HASH object @ 01806220

Why is it so? I guess, what I have in each line flowing "@" is not really a digest. Then, what is it? And how can I display MD5 digest here in this code?

My python version is Python 2.5 and the framework I am currently using is webapp (I have downloaded it together with SDK from "Google App Engine")

Answer 1

The hashlib.hash object doesn't implement its own __str__, so the default to-string operation is used, which prints the class name followed by its id (address).

(Use .hexdigest() to get the hex MD5 string.)

Answer 2

print m.hexdigest()

UPADATE: hexdigest() gives another representation of digest(). Every character in digest is transformed into its hex representation. You can transform it with the following function:

def digest_to_hex(chars):  
  res = ''  
  for c in chars:  
    res = res + '%02x' % ord(c)  
  return res

You can also use the generator expresion

''.join('%02x' % ord(x) for x in m.digest())

or

m.digest().encode('hex')

BTW: You can use dir(some_object) to get a list of its elements, and help(some_object) (in the interactive interpreter) to get more informations about it.