Object __hash__
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'''
This is an overview of Python object hashing. A hash, or hashmap, is a data structure
that maps a key to a value. A dict is Python's implementation of a hashmap:
dict = {
'key': 'value'
'key_2': 'value_2'
'key_3': 'value_3'
...
'key_n': 'value_n'
}
When you try to access something in a dict, Python internally runs hash() on the key
you provide so it doesn't have to run a comparison against every key in the dict. Dicts
provide a space denoted by a hash value for each (key, value) pairing, and so
the keys do not have to be sequentially searched.
For example:
hash('key') == 6017861245500558313
dict['key'] --> Python asks 'okay, do I have a space allocated for 6017861245500558313'?
--> yes! return 'value'!
Objects, however, have many methods and properties; hashing them requires a custom
__hash__ implementation. Below are implementations of custom __hash__ and __eq__
methods.
'''
class a:
def __init__(self, n):
self.n = n
def __keys__(self):
return self.n
def __eq__(self, other):
return self.n == other.n
def __hash__(self):
return hash(self.__keys__())
b = a(1)
c = a(2)
print(hash(b), hash(c))
print(b == c)
Python
INFO