.. Comment: this file is automatically generated by `update_example_docs.py`.
It should not be modified manually.
.. _example-category-custom_constructors:
Custom constructors
===================
:func:`tyro.cli` aims for comprehensive support of standard Python type
constructs. It can still, however, be useful to extend the set of suported
types.
We provide two complementary approaches for doing so:
- :mod:`tyro.conf` provides a simple API for specifying custom constructor
functions.
- :mod:`tyro.constructors` provides a more flexible API for defining behavior
for different types. There are two categories of types: *primitive* types are
instantiated from a single commandline argument, while *struct* types are
broken down into multiple arguments.
.. warning::
Custom constructors are useful, but can be verbose and require care. We
recommend using them sparingly.
.. _example-01_simple_constructors:
Simple constructors
-------------------
For simple custom constructors, we can pass a constructor function into
:func:`tyro.conf.arg` or :func:`tyro.conf.subcommand`. Arguments will be
generated by parsing the signature of the constructor function.
In this example, we define custom behavior for instantiating a NumPy array.
.. code-block:: python
:linenos:
# 01_simple_constructors.py
from typing import Literal
import numpy as np
from typing_extensions import Annotated
import tyro
def construct_array(
values: tuple[float, ...], dtype: Literal["float32", "float64"] = "float64"
) -> np.ndarray:
"""A custom constructor for 1D NumPy arrays."""
return np.array(
values,
dtype={"float32": np.float32, "float64": np.float64}[dtype],
)
def main(
# We can specify a custom constructor for an argument in `tyro.conf.arg()`.
array: Annotated[np.ndarray, tyro.conf.arg(constructor=construct_array)],
) -> None:
print(f"{array=}")
if __name__ == "__main__":
tyro.cli(main)
.. raw:: html
$ python ./01_simple_constructors.py --help
usage: ./01_simple_constructors.py [-h] --array.values [FLOAT [FLOAT ...]] [--array.dtype {float32,float64}]
╭─ options ───────────────────────────────────╮
│ -h, --help show this help message and exit │
╰─────────────────────────────────────────────╯
╭─ array options ─────────────────────────────╮
│ A custom constructor for 1D NumPy arrays. │
│ ─────────────────────────────────────────── │
│ --array.values [FLOAT [FLOAT ...]] │
│ (required) │
│ --array.dtype {float32,float64} │
│ (default: float64) │
╰─────────────────────────────────────────────╯
.. raw:: html
$ python ./01_simple_constructors.py --array.values 1 2 3
array=array([1., 2., 3.])
.. raw:: html
$ python ./01_simple_constructors.py --array.values 1 2 3 4 5 --array.dtype float32
array=array([1., 2., 3., 4., 5.], dtype=float32)
.. _example-02_primitive_annotation:
Custom primitive
----------------
In this example, we use :mod:`tyro.constructors` to attach a primitive
constructor via a runtime annotation.
.. code-block:: python
:linenos:
# 02_primitive_annotation.py
import json
from typing_extensions import Annotated
import tyro
# A dictionary type, but `tyro` will expect a JSON string from the CLI.
JsonDict = Annotated[
dict,
tyro.constructors.PrimitiveConstructorSpec(
# Number of arguments to consume.
nargs=1,
# Argument name in usage messages.
metavar="JSON",
# Convert a list of strings to an instance. The length of the list
# should match `nargs`.
instance_from_str=lambda args: json.loads(args[0]),
# Check if an instance is of the expected type. This is only used for
# helptext formatting in the presence of union types.
is_instance=lambda instance: isinstance(instance, dict),
# Convert an instance to a list of strings. This is used for handling
# default values that are set in Python. The length of the list should
# match `nargs`.
str_from_instance=lambda instance: [json.dumps(instance)],
),
]
def main(
dict1: JsonDict,
dict2: JsonDict = {"default": None},
) -> None:
print(f"{dict1=}")
print(f"{dict2=}")
if __name__ == "__main__":
tyro.cli(main)
.. raw:: html
$ python ./02_primitive_annotation.py --help
usage: ./02_primitive_annotation.py [-h] --dict1 JSON [--dict2 JSON]
╭─ options ─────────────────────────────────────╮
│ -h, --help show this help message and exit │
│ --dict1 JSON (required) │
│ --dict2 JSON (default: '{"default": null}') │
╰───────────────────────────────────────────────╯
.. raw:: html
$ python ./02_primitive_annotation.py --dict1 '{"hello": "world"}'
dict1={'hello': 'world'}
dict2={'default': None}
.. raw:: html
$ python ./02_primitive_annotation.py --dict1 '{"hello": "world"}' --dict2 '{"hello": "world"}'
dict1={'hello': 'world'}
dict2={'hello': 'world'}
.. _example-03_primitive_registry:
Custom primitive (registry)
---------------------------
In this example, we use a :class:`tyro.constructors.ConstructorRegistry` to
define a rule that applies to all types that match ``dict[str, Any]``.
.. code-block:: python
:linenos:
# 03_primitive_registry.py
import json
from typing import Any
import tyro
# Create a custom registry, which stores constructor rules.
custom_registry = tyro.constructors.ConstructorRegistry()
# Define a rule that applies to all types that match `dict[str, Any]`.
@custom_registry.primitive_rule
def _(
type_info: tyro.constructors.PrimitiveTypeInfo,
) -> tyro.constructors.PrimitiveConstructorSpec | None:
# We return `None` if the rule does not apply.
if type_info.type != dict[str, Any]:
return None
# If the rule applies, we return the constructor spec.
return tyro.constructors.PrimitiveConstructorSpec(
nargs=1,
metavar="JSON",
instance_from_str=lambda args: json.loads(args[0]),
is_instance=lambda instance: isinstance(instance, dict),
str_from_instance=lambda instance: [json.dumps(instance)],
)
def main(
dict1: dict[str, Any],
dict2: dict[str, Any] = {"default": None},
) -> None:
"""A function with two arguments, which can be populated from the CLI via JSON."""
print(f"{dict1=}")
print(f"{dict2=}")
if __name__ == "__main__":
# Pass the registry directly to tyro.cli().
tyro.cli(main, registry=custom_registry)
.. raw:: html
$ python ./03_primitive_registry.py --help
usage: ./03_primitive_registry.py [-h] --dict1 JSON [--dict2 JSON]
A function with two arguments, which can be populated from the CLI via JSON.
╭─ options ─────────────────────────────────────╮
│ -h, --help show this help message and exit │
│ --dict1 JSON (required) │
│ --dict2 JSON (default: '{"default": null}') │
╰───────────────────────────────────────────────╯
.. raw:: html
$ python ./03_primitive_registry.py --dict1 '{"hello": "world"}'
dict1={'hello': 'world'}
dict2={'default': None}
.. raw:: html
$ python ./03_primitive_registry.py --dict1 '{"hello": "world"}' --dict2 '{"hello": "world"}'
dict1={'hello': 'world'}
dict2={'hello': 'world'}
.. _example-04_struct_registry:
Custom structs (registry)
-------------------------
In this example, we use a :class:`tyro.constructors.ConstructorRegistry` to
add support for a custom struct type. Each struct type is broken down into
multiple fields, which themselves can be either primitive types or nested
structs.
.. warning::
This will be complicated!
.. code-block:: python
:linenos:
# 04_struct_registry.py
import tyro
# A custom type that we'll add support for to tyro.
class Bounds:
def __init__(self, lower: int, upper: int):
self.bounds = (lower, upper)
def __repr__(self) -> str:
return f"(lower={self.bounds[0]}, upper={self.bounds[1]})"
# Create a custom registry, which stores constructor rules.
custom_registry = tyro.constructors.ConstructorRegistry()
# Define a rule that applies to all types that match `Bounds`.
@custom_registry.struct_rule
def _(
type_info: tyro.constructors.StructTypeInfo,
) -> tyro.constructors.StructConstructorSpec | None:
# We return `None` if the rule does not apply.
if type_info.type != Bounds:
return None
# We can extract the default value of the field from `type_info`.
if isinstance(type_info.default, Bounds):
# If the default value is a `Bounds` instance, we don't need to generate a constructor.
default = (type_info.default.bounds[0], type_info.default.bounds[1])
else:
# Otherwise, the default value is missing. We'll mark the child defaults as missing as well.
assert type_info.default in (
tyro.constructors.MISSING,
tyro.constructors.MISSING_NONPROP,
)
default = (tyro.MISSING, tyro.MISSING)
# If the rule applies, we return the constructor spec.
return tyro.constructors.StructConstructorSpec(
# The instantiate function will be called with the fields as keyword arguments.
instantiate=Bounds,
fields=(
tyro.constructors.StructFieldSpec(
name="lower",
type=int,
default=default[0],
helptext="Lower bound.",
),
tyro.constructors.StructFieldSpec(
name="upper",
type=int,
default=default[1],
helptext="Upper bound.",
),
),
)
def main(
bounds: Bounds,
bounds_with_default: Bounds = Bounds(0, 100),
) -> None:
"""A function with two `Bounds` instances as input."""
print(f"{bounds=}")
print(f"{bounds_with_default=}")
if __name__ == "__main__":
# Pass the registry directly to tyro.cli().
tyro.cli(main, registry=custom_registry)
.. raw:: html
$ python ./04_struct_registry.py --help
usage: ./04_struct_registry.py [-h] [OPTIONS]
A function with two `Bounds` instances as input.
╭─ options ───────────────────────────────────────────╮
│ -h, --help show this help message and exit │
╰─────────────────────────────────────────────────────╯
╭─ bounds options ────────────────────────────────────╮
│ --bounds.lower INT Lower bound. (required) │
│ --bounds.upper INT Upper bound. (required) │
╰─────────────────────────────────────────────────────╯
╭─ bounds-with-default options ───────────────────────╮
│ --bounds-with-default.lower INT │
│ Lower bound. (default: 0) │
│ --bounds-with-default.upper INT │
│ Upper bound. (default: 100) │
╰─────────────────────────────────────────────────────╯
.. raw:: html
$ python ./04_struct_registry.py --bounds.lower 5 --bounds.upper 10
bounds=(lower=5, upper=10)
bounds_with_default=(lower=0, upper=100)