I want to hash a simple array of strings
The documentation says you can't simple feed a string into hashlib's update() function,
so I tried a regular variable, but then I got the TypeError: object supporting the buffer API required error.
Here's what I had so far
def generateHash(data):
# Prepare the project id hash
hashId = hashlib.md5()
hashId.update(data)
return hashId.hexdigest()
You can use the repr() function to get the (Unicode) string representation of the array (or of whatever object that implements conversion to a representation). Then you encode the string to UTF-8 (the order of bytes is the same everywhere when using UTF-8). The resulting bytes can be hashed as you tried above:
#!python3
import hashlib
def hashFor(data):
# Prepare the project id hash
hashId = hashlib.md5()
hashId.update(repr(data).encode('utf-8'))
return hashId.hexdigest()
if __name__ == '__main__':
data1 = ['abc', 'de']
data2 = ['a', 'bcde']
print(hashFor(data1) + ':', data1)
print(hashFor(data2) + ':', data2)
It prints on my console:
c:\tmp\___python\skerit\so17412304>py a.py
d26d27d8cbb7c6fe50637155c21d5af6: ['abc', 'de']
dbd5ab5df464b8bcee61fe8357f07b6e: ['a', 'bcde']
__repr__ returns something that's a useful input for the hash function. hashlib objects themselves, for example, repr() to '<md5 HASH object @ 0x7fb503555a80>'. Even ignoring the nasty implications if this were used for some cryptographic operation, this isn't even deterministic! The same program run at different times won't return the same hash value.
",".join(data) as __repr__ isn't guaranteed to be consistent with future versions. Maybe Python 4 will return a slightly different string (e.g. s'abc instead of 'abc').','.join(data) is buggy as ['a,', 'bb'] would produce the same result as ['a', ',bb']. But you are right. Any suitable function that captures the representation of the array of strings and returns it as bytes can be used for calculating the hash value.Depending on what you want to do, getting the hash of all strings concatenated or hash of each string separately. you can get the fist following Thomas solution as m.update(a); m.update(b) is equivalent to m.update(a+b). Or the later following below solution
def generateHash(data):
# Prepare the project id hash
return [hashlib.md5(i.encode('utf-8')).hexdigest() for i in data]
Note that it returns a list. Each element is hash of a corresponding element in the given string list
If you'd like to hash a list of strings, a naive solution could be:
def hash_string_list(string_list):
h = hashlib.md5()
for s in string_list: # Note that you could use ''.join(string_list) instead
h.update(s) # s.encode('utf-8') if you're using Python 3
return h.hexdigest()
However, be wary that ['abc', 'efg'] and ['a', 'bcefg'] would hash to the same value.
If you provide more context regarding your objective, other solutions might be more appropriate.
update takes bytes, so if you have strings you need to encode them first.