Module `astrapy.utils.str_enum`

Expand source code

# Copyright DataStax, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

from __future__ import annotations

from enum import Enum
from typing import TypeVar

T = TypeVar("T", bound="StrEnum")


class StrEnum(Enum):
    @classmethod
    def coerce(cls: type[T], value: str | T) -> T:
        """
        Accepts either a string or an instance of the Enum itself.
        If a string is passed, it converts it to the corresponding
        Enum value (case-insensitive).
        If an Enum instance is passed, it returns it as-is.
        Raises ValueError if the string does not match any enum member.
        """

        if isinstance(value, cls):
            return value
        elif isinstance(value, str):
            try:
                return cls[value.upper()]
            except KeyError:
                raise ValueError(
                    f"Invalid value '{value}' for {cls.__name__}. "
                    f"Allowed values are: {[e.name.lower() for e in cls]}"
                )
        raise ValueError(
            f"Invalid value '{value}' for {cls.__name__}. "
            f"Allowed values are: {[e.name.lower() for e in cls]}"
        )

Classes

class StrEnum (*args, **kwds)

Create a collection of name/value pairs.

Example enumeration:

>>> class Color(Enum):
...     RED = 1
...     BLUE = 2
...     GREEN = 3

Access them by:

attribute access::

>>> Color.RED
<Color.RED: 1>

value lookup:

>>> Color(1)
<Color.RED: 1>

name lookup:

>>> Color['RED']
<Color.RED: 1>

Enumerations can be iterated over, and know how many members they have:

>>> len(Color)
3

>>> list(Color)
[<Color.RED: 1>, <Color.BLUE: 2>, <Color.GREEN: 3>]

Methods can be added to enumerations, and members can have their own attributes – see the documentation for details.

Expand source code

class StrEnum(Enum):
    @classmethod
    def coerce(cls: type[T], value: str | T) -> T:
        """
        Accepts either a string or an instance of the Enum itself.
        If a string is passed, it converts it to the corresponding
        Enum value (case-insensitive).
        If an Enum instance is passed, it returns it as-is.
        Raises ValueError if the string does not match any enum member.
        """

        if isinstance(value, cls):
            return value
        elif isinstance(value, str):
            try:
                return cls[value.upper()]
            except KeyError:
                raise ValueError(
                    f"Invalid value '{value}' for {cls.__name__}. "
                    f"Allowed values are: {[e.name.lower() for e in cls]}"
                )
        raise ValueError(
            f"Invalid value '{value}' for {cls.__name__}. "
            f"Allowed values are: {[e.name.lower() for e in cls]}"
        )

Ancestors

enum.Enum

Subclasses

Static methods

def coerce(value: str | T) ‑> ~T

Accepts either a string or an instance of the Enum itself. If a string is passed, it converts it to the corresponding Enum value (case-insensitive). If an Enum instance is passed, it returns it as-is. Raises ValueError if the string does not match any enum member.

Expand source code

@classmethod
def coerce(cls: type[T], value: str | T) -> T:
    """
    Accepts either a string or an instance of the Enum itself.
    If a string is passed, it converts it to the corresponding
    Enum value (case-insensitive).
    If an Enum instance is passed, it returns it as-is.
    Raises ValueError if the string does not match any enum member.
    """

    if isinstance(value, cls):
        return value
    elif isinstance(value, str):
        try:
            return cls[value.upper()]
        except KeyError:
            raise ValueError(
                f"Invalid value '{value}' for {cls.__name__}. "
                f"Allowed values are: {[e.name.lower() for e in cls]}"
            )
    raise ValueError(
        f"Invalid value '{value}' for {cls.__name__}. "
        f"Allowed values are: {[e.name.lower() for e in cls]}"
    )