To define a CLI parameter that can take a value from a predefined set of values you can use a standard Python enum.Enum:

{!../docs_src/parameter_types/enum/tutorial001.py!}

!!! tip Notice that the function parameter network will be an Enum, not a str.

To get the `str` value in your function's code use `network.value`.

Check it:

$ python main.py --help

// Notice the predefined values [simple|conv|lstm]
Usage: main.py [OPTIONS]

Options:
  --network [simple|conv|lstm]  [default: simple]
  --help                        Show this message and exit.

// Try it
$ python main.py --network conv

Training neural network of type: conv

// Invalid value
$ python main.py --network capsule

Usage: main.py [OPTIONS]
Try "main.py --help" for help.

Error: Invalid value for '--network': 'capsule' is not one of 'simple', 'conv', 'lstm'.

// Note that enums are case sensitive by default
$ python main.py --network CONV

Usage: main.py [OPTIONS]
Try "main.py --help" for help.

Error: Invalid value for '--network': 'CONV' is not one of 'simple', 'conv', 'lstm'.

Case insensitive Enum choices

You can make an Enum (choice) CLI parameter be case-insensitive with the case_sensitive parameter:

=== "Python 3.7+"

```Python hl_lines="15"
{!> ../docs_src/parameter_types/enum/tutorial002_an.py!}
```

=== "Python 3.7+ non-Annotated"

!!! tip
    Prefer to use the `Annotated` version if possible.

```Python hl_lines="13"
{!> ../docs_src/parameter_types/enum/tutorial002.py!}
```

And then the values of the Enum will be checked no matter if lower case, upper case, or a mix:

// Notice the upper case CONV
$ python main.py --network CONV

Training neural network of type: conv

// A mix also works
$ python main.py --network LsTm

Training neural network of type: lstm

List of Enum values

A CLI parameter can also take a list of Enum values:

=== "Python 3.7+"

```Python hl_lines="14"
{!> ../docs_src/parameter_types/enum/tutorial003_an.py!}
```

=== "Python 3.7+ non-Annotated"

!!! tip
    Prefer to use the `Annotated` version if possible.

```Python hl_lines="13"
{!> ../docs_src/parameter_types/enum/tutorial003.py!}
```

This works just like any other parameter value taking a list of things:

$ python main.py --help

// Notice the default values being shown
Usage: main.py [OPTIONS]

Options:
  --groceries [Eggs|Bacon|Cheese]  [default: Eggs, Cheese]
  --help                           Show this message and exit.

// Try it with the default values
$ python main.py

Buying groceries: Eggs, Cheese

// Try it with a single value
$ python main.py --groceries "Eggs"

Buying groceries: Eggs

// Try it with multiple values
$ python main.py --groceries "Eggs" --groceries "Bacon"

Buying groceries: Eggs, Bacon