Learning Python. I was learning reduce() and was playing with the initialization parameter. The code simply outputs a SHA256 hash of a list of strings. At first I used a for loop to generate the hash. Then, I used functools.reduce() to try and do the same thing.
import functools
import hashlib
def hash_two_strings(a,b):
c = a + b
h = hashlib.sha256(c.encode()).hexdigest()
return h
c1 = ['3', 'sha256', 'C=US,O=Entrust', 'CN=review.mysite.com', '1c:08:ea:51', '2/11/2022', '2/11/2023', 'RSA', '2048']
h = hashlib.md5(c1[0].encode()).hexdigest()
for i in range(1, len(c1)):
s = h+c1[i]
h = hashlib.sha256(s.encode()).hexdigest()
print (h)
h = functools.reduce(lambda a, b: hash_two_strings, c1[1:], hashlib.sha256(c1[0].encode()).hexdigest())
print (h)
Output: 2b9d651fee9c0ddc75477be6dba8d1d3600551cf2e355e9f4788d3c728d237a3 <function hash_two_strings at 0x000001FF9B6A3E20>
However, reduce() seems to want to return a reference to the function I wrote hash_two_strings(), not the actual hash I was expecting. Any thoughts on how I'm using reduce() incorrectly because I can't see it.
There are two ways to fix your problem:
h = functools.reduce(hash_two_strings, c1[1:], hashlib.sha256(c1[0].encode()).hexdigest())
print (h)
Or:
h = functools.reduce(lambda a, b: hash_two_strings(a, b), c1[1:], hashlib.sha256(c1[0].encode()).hexdigest())
Because lambda as you used it before ignored the a,b arguments and just returned the hash_two_strings function object.
Remember that if you write function without the parenthesis that is just a function object, not the result of calling the function:
>>> def round_3_point_5(): return round(3.5)
...
>>> round_3_point_5
<function round_3_point_5 at 0x7f04d347b700>
>>> round_3_point_5()
4