Enum mappings

Define Enum mappings

You can define a mapping between two Enum classes using the create_enum_mapper() function.

>>> class ProgrammingLanguage(Enum):
...     PYTHON = auto()
...     JAVA = auto()
...     CPLUSPLUS = auto()
>>>
>>> class FileEndings(str, Enum):
...    PY = ".py"
...    JAVA = ".java"
...    CPP = ".cpp"
...    H = ".h"
>>>
>>> create_enum_mapper(FileEndings, ProgrammingLanguage,
...     {
...         FileEndings.PY: ProgrammingLanguage.PYTHON,
...         FileEndings.CPP: ProgrammingLanguage.CPLUSPLUS,
...         FileEndings.H: ProgrammingLanguage.CPLUSPLUS
...     }
... )

Here a mapping from the enum FileEndings to the enum ProgrammingLanguage is defined.

Notice, that the order of the mapping is defined in the opposite way in comparison to the dataclass mappers. For each member of the source enum, you have to list the member of the target enum. That way you can also map multiple source members to the same target member. In the example both FileEndings.CPP and FileEndings.H are mapped to ProgrammingLanguage.CPLUSPLUS.

The library will analyze both enums, and will create a mapper function(s) that you can use use later to convert / overwrite an object using the typical map_to() function.

>>> map_to(FileEndings.PY, ProgrammingLanguage)
<ProgrammingLanguage.PYTHON: 1>

It’s also possible to specify the target members as strings instead of the actual values.

>>> create_enum_mapper(FileEndings, ProgrammingLanguage, {"PY": "PYTHON", "CPP": "CPLUSPLUS", "H": "CPLUSPLUS"})
>>>
>>> map_to(FileEndings.PY, ProgrammingLanguage)
<ProgrammingLanguage.PYTHON: 1>

As always, if enum members have the same name, you don’t need specify them in the mapping. And the library will make sure, that you don’t forget any enum values.

Define enum mappings via decorators

Instead of using the create_enum_mapper() function, you can also use the enum_mapper() and enum_mapper_from() decorators as shortcuts. They take the same parameters, and are equivalent to the create_enum_mapper() function.

You will however have to use strings for the fields of the current class, because Python doesn’t know about them yet. However be assured, that the library will warn you when you misspell or forget some fields.

>>> @enum_mapper(ProgrammingLanguage, {"PY": ProgrammingLanguage.PYTHON, "CPP": ProgrammingLanguage.CPLUSPLUS, "H": ProgrammingLanguage.CPLUSPLUS})
... class FileEndings(str, Enum):
...    PY = ".py"
...    JAVA = ".java"
...    CPP = ".cpp"
...    H = ".h"
>>>
>>> map_to(FileEndings.PY, ProgrammingLanguage)
<ProgrammingLanguage.PYTHON: 1>

>>> @enum_mapper_from(FileEndings, {FileEndings.PY: "PYTHON", FileEndings.CPP: "CPLUSPLUS", FileEndings.H: "CPLUSPLUS"})
... class ProgrammingLanguage(Enum):
...     PYTHON = auto()
...     JAVA = auto()
...     CPLUSPLUS = auto()
>>>
>>> map_to(FileEndings.PY, ProgrammingLanguage)
<ProgrammingLanguage.PYTHON: 1>