gloss

Gloss (short for glossary) is a different kind of dictionary. All values also automatically become keys and so can be looked up in the Gloss to find its corresponding 'key'. This makes it easy to lookup and maintain one-to-one relationships such as a label to a certain magnitude.

Gloss is a MutableMapping and supports all the same methods that dict does.

Examples

from gloss import Gloss

example = Gloss()
example["stdin"] = 0
example.update({"stdout": 1, "stderr": 2})
print(example)
#Gloss({"stdin": 0, "stdout": 1, "stderr": 2})
print(example[1], "goes to" example["stderr"])
#stdout goes to 2
example[3] = "config.toml"
example[1] = "shell pipe"
print(example)
#Gloss({"stdin": 0, "stderr": 2, "config.toml": 3, "shell pipe": 1})
print([fd_or_desc for fd_or_desc in example])
#["stdin", "stderr", "config.toml", "shell pipe", 0, 1, 2, 3]

As both the key and value are gettable items from the Gloss and are indistinguishable once added, term is the preferred name for items in a Gloss, and a term pair is the 1-1 mapping each term belongs to.

Differences from Enum

Enum is a wonderful data structure that also supports 1-1 mappings and it's already built into Python. However, these limitations of Enums are solved by Gloss:

• enum members are static. They are defined all at once in the class and their values cannot change. A Gloss on the other hand can be added to, altered, even have members deleted or popped, all at runtime
• Accessing Enum member names and their values are different operations. Looking up a member by name is done with either dot dereference or getitem; looking up a member by value is done with a call. With a Gloss you don't have to know which side of the mapping your key is on (if there even is a distinction to the mapping), it is all done by getitem
• One side of an enum mapping must be a string. Because member names are attributes they must follow Python identifier naming rules. In a Gloss, all terms may be any hashable object

Differences from Dict

While the classic dict solves some of the limitations of using an Enum, primarily being mutable at runtime, it is not a 1-1 mapping.

• enforcing uniqueness among dict values is a lot of extra work
• looking up a dict value is O(n). Therefore so is updating, deleting, popping, etc that value. Searching a Gloss for any term is O(1) time
• updating any term in a Gloss takes a single operation