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""" A dictionary with string keys. This implementation that avoids conveniences like `index` and `enumerate`. """
class EmptyClass:
def __repr__(self):
return "Empty"
Empty = EmptyClass()
def array_index(array, key, i):
while True:
if array[i] == key:
return i
elif array[i] == Empty:
raise ValueError(f"Value {key} is not in the dictionary")
i = (i + 1) % len(array)
def djb2_hash(key):
h = 5381
for c in key:
h = ((h << 5 + h) + ord(c)) & 0xffffffff
return h
start = djb2_hash
class Hashtable:
def __init__(self, size):
self.keys = [Empty] * size
self.values = [Empty] * size
def __getitem__(self, key):
return self.values[array_index(self.keys, key, start(key) % len(self.keys))]
def __setitem__(self, key, value):
try:
i = array_index(self.keys, key, start(key) % len(self.keys))
except ValueError:
i = array_index(self.keys, Empty, start(key) % len(self.keys))
self.keys[i] = key
self.values[i] = value
if __name__ == '__main__':
d = Hashtable(100)
d["hello"] = 10
d["world"] = "foo"
print(d["hello"])