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# marshmallow-enum
Enum field for use with Marshmallow.
## Installation
```bash
pip install --user marshmallow_enum
```
If you're on a version before 3.4, you'll also need to install `enum34`.
## Using The Field
To make use of the field, you must have an existing Enum:
```python
from enum import Enum
class StopLight(Enum):
green = 1
yellow = 2
red = 3
```
Then, declare it as a field in a schema:
```python
from marshmallow import Schema
from marshmallow_enum import EnumField
class TrafficStop(Schema):
light_color = EnumField(StopLight)
```
By default, the field will load and dump based on the _name_ given to an enum value.
```python
schema = TrafficStop()
schema.dump({'light_color': EnumField.red}).data
# {'light_color': 'red'}
schema.load({'light_color': 'red'}).data
# {'light_color': StopLight.red}
```
### Customizing loading and dumping behavior
To customize how an enum is serialized or deserialized, there are three options:
- Setting `by_value=True`. This will cause both dumping and loading to use the value of the enum.
- Setting `load_by=EnumField.VALUE`. This will cause loading to use the value of the enum.
- Setting `dump_by=EnumField.VALUE`. This will cause dumping to use the value of the enum.
If either `load_by` or `dump_by` are unset, they will follow from `by_value`.
Additionally, there is `EnumField.NAME` to be explicit about the load and dump behavior, this
is the same as leaving both `by_value` and either `load_by` and/or `dump_by` unset.
### Custom Error Message
A custom error message can be provided via the `error` keyword argument. It can accept three
format values:
- `{input}`: The value provided to the schema field
- `{names}`: The names of the individual enum members
- `{values}`: The values of the individual enum members
Previously, the following inputs were also available but are deprecated and will be removed in 1.6:
- `{name}`
- `{value}`
- `{choices}`
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