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Decorator

danling.utils.decorators

flexible_decorator

Python
1
flexible_decorator(maybe_decorator: Optional[Callable] = None)

Meta decorator to allow bracket-less decorator when no arguments are passed.

Examples:

For decorator defined as follows:

Python Console Session
>>> @flexible_decorator
... def decorator(*args, **kwargs):
...     def wrapper(func, *args, **kwargs):
...         pass
...     return wrapper

The following two are equivalent:

Python Console Session
>>> @decorator
... def func(*args, **kwargs):
...     pass
Python Console Session
>>> @decorator()
... def func(*args, **kwargs):
...     pass
Source code in danling/utils/decorators.py
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def flexible_decorator(maybe_decorator: Optional[Callable] = None):
    r"""
    Meta decorator to allow bracket-less decorator when no arguments are passed.

    Examples:
        For decorator defined as follows:

        >>> @flexible_decorator
        ... def decorator(*args, **kwargs):
        ...     def wrapper(func, *args, **kwargs):
        ...         pass
        ...     return wrapper

        The following two are equivalent:

        >>> @decorator
        ... def func(*args, **kwargs):
        ...     pass

        >>> @decorator()
        ... def func(*args, **kwargs):
        ...     pass
    """

    def decorator(func: Callable):
        @wraps(func)
        def wrapper(*args, **kwargs):
            if len(args) == 1 and isfunction(args[0]):
                return func(**kwargs)(args[0])
            return func(*args, **kwargs)

        return wrapper

    if maybe_decorator is None:
        return decorator
    return decorator(maybe_decorator)

print_exc

Python
1
print_exc(exc, func, args, kwargs, verbosity: int = 40)

Print exception raised by func with args and kwargs to stderr. This function serves as the default callback for catch.

Parameters:

Name Type Description Default
verbosity int

What level of traceback to print. 0-: No traceback. 0-10: Full information of arguments and key word arguments. 10-20: Stack trace to function calls. 40+: Function name and error messages.

 40
Source code in danling/utils/decorators.py
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def print_exc(exc, func, args, kwargs, verbosity: int = 40):  # pylint: disable=W0613
    r"""
    Print exception raised by `func` with `args` and `kwargs` to `stderr`.
    This function serves as the default callback for catch.

    Args:
        verbosity: What level of traceback to print.
            0-: No traceback.
            0-10: Full information of arguments and key word arguments.
            10-20: Stack trace to function calls.
            40+: Function name and error messages.
    """

    if verbosity >= 0:
        message = traceback.format_exc()
        message += f"\nencoutered when calling {func}"
        if verbosity <= 20:
            message += "\n\nstack:\n" + "\n".join(traceback.format_stack()[:-2])
        if verbosity <= 10:
            message += "\n" + f"args: {args}\nkwargs: {kwargs}"
        try:
            print(message, file=stderr, force=True)  # type: ignore
        except TypeError:
            print(message, file=stderr)

catch

Python
1
catch(error: Exceptions = Exception, exclude: Exceptions | None = None, callback: Callable = print_exc, *callback_args, **callback_kwargs)

Decorator to catch error except for exclude. Detailed traceback will be printed to stderr.

catch is extremely useful for unfatal errors. For example, Runner saves checkpoint regularly, however, this might break running if the space is full. Decorating save method with catch will allow you to catch these errors and continue your running.

Parameters:

Name Type Description Default
error Exceptions

Exceptions to be caught.

 Exception
exclude Exceptions | None

Exceptions to be excluded.

 None
callback Callable

Callback to be called when an error occurs. The first four arguments to callback are exc, func, args, kwargs. Additional arguments should be passed with *callback_args and **callback_kwargs.

 print_exc
callback_args

Arguments to be passed to callback.

 ()
callback_kwargs

Keyword arguments to be passed to callback.

 {}

Examples:

Python Console Session
>>> def file_not_found(*args, **kwargs):
...     raise FileNotFoundError
>>> func = file_not_found
>>> func()
Traceback (most recent call last):
FileNotFoundError
>>> func = catch(OSError)(file_not_found)
>>> func()
>>> func = catch(IOError)(file_not_found)
>>> func()
>>> func = catch(ZeroDivisionError)(file_not_found)
>>> func()
Traceback (most recent call last):
FileNotFoundError
Source code in danling/utils/decorators.py
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@flexible_decorator
def catch(  # pylint: disable=keyword-arg-before-vararg
    error: Exceptions = Exception,
    exclude: Exceptions | None = None,
    callback: Callable = print_exc,
    *callback_args,
    **callback_kwargs,
):
    r"""
    Decorator to catch `error` except for `exclude`.
    Detailed traceback will be printed to `stderr`.

    `catch` is extremely useful for unfatal errors.
    For example, `Runner` saves checkpoint regularly, however, this might break running if the space is full.
    Decorating `save` method with `catch` will allow you to catch these errors and continue your running.

    Args:
        error: Exceptions to be caught.
        exclude: Exceptions to be excluded.
        callback: Callback to be called when an error occurs.
            The first four arguments to `callback` are `exc`, `func`, `args`, `kwargs`.
            Additional arguments should be passed with `*callback_args` and `**callback_kwargs`.
        callback_args: Arguments to be passed to `callback`.
        callback_kwargs: Keyword arguments to be passed to `callback`.

    Examples:
        >>> def file_not_found(*args, **kwargs):
        ...     raise FileNotFoundError
        >>> func = file_not_found
        >>> func()
        Traceback (most recent call last):
        FileNotFoundError
        >>> func = catch(OSError)(file_not_found)
        >>> func()
        >>> func = catch(IOError)(file_not_found)
        >>> func()
        >>> func = catch(ZeroDivisionError)(file_not_found)
        >>> func()
        Traceback (most recent call last):
        FileNotFoundError
    """

    def decorator(func):
        @wraps(func)
        def wrapper(*args, **kwargs):  # pylint: disable=inconsistent-return-statements
            try:
                return func(*args, **kwargs)
            except error as exc:  # pylint: disable=broad-exception-caught
                if exclude is not None and isinstance(exc, exclude):
                    raise exc
                callback(exc, func, args, kwargs, *callback_args, **callback_kwargs)

        return wrapper

    decorator.__doc__ = catch.__doc__

    return decorator

method_cache

Python
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method_cache(maxsize: int | None = 128, typed: bool = False)

Decorator to cache the result of an instance method.

functools.lru_cache uses a strong reference to the instance, which will make the instance immortal and break the garbage collection.

method_cache uses a weak reference to the instance to resolve this issue.

See Also
Source code in danling/utils/decorators.py
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@flexible_decorator
def method_cache(maxsize: int | None = 128, typed: bool = False):
    r"""
    Decorator to cache the result of an instance method.

    `functools.lru_cache` uses a strong reference to the instance,
    which will make the instance immortal and break the garbage collection.

    `method_cache` uses a weak reference to the instance to resolve this issue.

    See Also:
        https://rednafi.github.io/reflections/dont-wrap-instance-methods-with-functoolslru_cache-decorator-in-python.html
    """

    def decorator(func):
        @wraps(func)
        def wrapper(self, *args, **kwargs):
            self_ref = ref(self)

            @wraps(func)
            @lru_cache(maxsize=maxsize, typed=typed)
            def cached_method(*args, **kwargs):
                return func(self_ref(), *args, **kwargs)

            setattr(self, func.__name__, cached_method)
            return cached_method(*args, **kwargs)

        return wrapper

    return decorator

ensure_dir

Python
1
ensure_dir(func)

Decorator to ensure a directory property exists.

Note

Please avoid using this with cached_property.

Examples:

Python Console Session
>>> @property
... @ensure_dir
... def dir(self) -> str:
...     return os.path.join("path", "to", "dir")
Source code in danling/utils/decorators.py
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def ensure_dir(func):
    r"""
    Decorator to ensure a directory property exists.

    Note:
        Please avoid using this with `cached_property`.

    Examples:
        >>> @property
        ... @ensure_dir
        ... def dir(self) -> str:
        ...     return os.path.join("path", "to", "dir")
    """

    @wraps(func)
    def wrapper(*args, **kwargs):
        path = abspath(func(*args, **kwargs))
        makedirs(path, exist_ok=True)
        return path

    return wrapper