automap is a Python package containing high-performance autoincremented
integer-valued mappings.
To install, just run pip install automap.
automap objects are sort of like "inverse sequences". They come in two
variants:
>>> from automap import FrozenAutoMapFrozenAutoMap objects are immutable. They can be constructed from any iterable
of hashable, unique keys.
>>> a = FrozenAutoMap("AAA")
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: 'A'
>>> a = FrozenAutoMap("ABC")
>>> a
automap.FrozenAutoMap(['A', 'B', 'C'])The values are integers, incrementing according to the order of the original keys:
>>> a["A"]
0
>>> a["C"]
2
>>> a["X"]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
KeyError: 'X'The full Mapping interface is provided:
>>> [*a.keys()]
['A', 'B', 'C']
>>> [*a.values()]
[0, 1, 2]
>>> [*a.items()]
[('A', 0), ('B', 1), ('C', 2)]
>>> a.get("X", 42)
42
>>> "B" in a
True
>>> [*a]
['A', 'B', 'C']They may also be combined with each other using the | operator:
>>> b = FrozenAutoMap(range(5))
>>> c = FrozenAutoMap(range(5, 10))
>>> b | c
automap.FrozenAutoMap([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
>>> b |= c # Note that b is reassigned, not mutated!
>>> b
automap.FrozenAutoMap([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])>>> from automap import AutoMapUnlike FrozenAutoMap objects, AutoMap objects can grow; new keys may be
added, but existing ones may not be deleted or changed.
>>> d = AutoMap("ABC")
>>> d
automap.AutoMap(['A', 'B', 'C'])
>>> d |= "DEF" # Here, d *is* mutated!
>>> d
automap.AutoMap(['A', 'B', 'C', 'D', 'E', 'F'])They also have add and update methods for adding new keys:
>>> e = AutoMap(["I", "II", "III"])
>>> e.add("IV")
>>> e
automap.AutoMap(['I', 'II', 'III', 'IV'])
>>> e.update(["V", "VI", "VII"])
>>> e
automap.AutoMap(['I', 'II', 'III', 'IV', 'V', 'VI', 'VII'])Tests show string-keyed AutoMap objects being created 70% faster and accessed
5% faster than the equivalent dict construction, on average. They also tend to
take up the same amount of memory. You can run invoke performance from this
repository to see the comparison on your machine.
More details on the design can be found in automap.c.