""" accessor.py contains base classes for implementing accessor properties that can be mixed into or pinned onto other pandas classes. """ from typing import FrozenSet, List, Set import warnings from pandas.util._decorators import doc class DirNamesMixin: _accessors: Set[str] = set() _hidden_attrs: FrozenSet[str] = frozenset() def _dir_deletions(self) -> Set[str]: """ Delete unwanted __dir__ for this object. """ return self._accessors | self._hidden_attrs def _dir_additions(self) -> Set[str]: """ Add additional __dir__ for this object. """ return {accessor for accessor in self._accessors if hasattr(self, accessor)} def __dir__(self) -> List[str]: """ Provide method name lookup and completion. Notes ----- Only provide 'public' methods. """ rv = set(super().__dir__()) rv = (rv - self._dir_deletions()) | self._dir_additions() return sorted(rv) class PandasDelegate: """ Abstract base class for delegating methods/properties. """ def _delegate_property_get(self, name, *args, **kwargs): raise TypeError(f"You cannot access the property {name}") def _delegate_property_set(self, name, value, *args, **kwargs): raise TypeError(f"The property {name} cannot be set") def _delegate_method(self, name, *args, **kwargs): raise TypeError(f"You cannot call method {name}") @classmethod def _add_delegate_accessors( cls, delegate, accessors, typ: str, overwrite: bool = False ): """ Add accessors to cls from the delegate class. Parameters ---------- cls Class to add the methods/properties to. delegate Class to get methods/properties and doc-strings. accessors : list of str List of accessors to add. typ : {'property', 'method'} overwrite : bool, default False Overwrite the method/property in the target class if it exists. """ def _create_delegator_property(name): def _getter(self): return self._delegate_property_get(name) def _setter(self, new_values): return self._delegate_property_set(name, new_values) _getter.__name__ = name _setter.__name__ = name return property( fget=_getter, fset=_setter, doc=getattr(delegate, name).__doc__ ) def _create_delegator_method(name): def f(self, *args, **kwargs): return self._delegate_method(name, *args, **kwargs) f.__name__ = name f.__doc__ = getattr(delegate, name).__doc__ return f for name in accessors: if typ == "property": f = _create_delegator_property(name) else: f = _create_delegator_method(name) # don't overwrite existing methods/properties if overwrite or not hasattr(cls, name): setattr(cls, name, f) def delegate_names(delegate, accessors, typ: str, overwrite: bool = False): """ Add delegated names to a class using a class decorator. This provides an alternative usage to directly calling `_add_delegate_accessors` below a class definition. Parameters ---------- delegate : object The class to get methods/properties & doc-strings. accessors : Sequence[str] List of accessor to add. typ : {'property', 'method'} overwrite : bool, default False Overwrite the method/property in the target class if it exists. Returns ------- callable A class decorator. Examples -------- @delegate_names(Categorical, ["categories", "ordered"], "property") class CategoricalAccessor(PandasDelegate): [...] """ def add_delegate_accessors(cls): cls._add_delegate_accessors(delegate, accessors, typ, overwrite=overwrite) return cls return add_delegate_accessors # Ported with modifications from xarray # https://github.com/pydata/xarray/blob/master/xarray/core/extensions.py # 1. We don't need to catch and re-raise AttributeErrors as RuntimeErrors # 2. We use a UserWarning instead of a custom Warning class CachedAccessor: """ Custom property-like object. A descriptor for caching accessors. Parameters ---------- name : str Namespace that will be accessed under, e.g. ``df.foo``. accessor : cls Class with the extension methods. Notes ----- For accessor, The class's __init__ method assumes that one of ``Series``, ``DataFrame`` or ``Index`` as the single argument ``data``. """ def __init__(self, name: str, accessor) -> None: self._name = name self._accessor = accessor def __get__(self, obj, cls): if obj is None: # we're accessing the attribute of the class, i.e., Dataset.geo return self._accessor accessor_obj = self._accessor(obj) # Replace the property with the accessor object. Inspired by: # https://www.pydanny.com/cached-property.html # We need to use object.__setattr__ because we overwrite __setattr__ on # NDFrame object.__setattr__(obj, self._name, accessor_obj) return accessor_obj @doc(klass="", others="") def _register_accessor(name, cls): """ Register a custom accessor on {klass} objects. Parameters ---------- name : str Name under which the accessor should be registered. A warning is issued if this name conflicts with a preexisting attribute. Returns ------- callable A class decorator. See Also -------- register_dataframe_accessor : Register a custom accessor on DataFrame objects. register_series_accessor : Register a custom accessor on Series objects. register_index_accessor : Register a custom accessor on Index objects. Notes ----- When accessed, your accessor will be initialized with the pandas object the user is interacting with. So the signature must be .. code-block:: python def __init__(self, pandas_object): # noqa: E999 ... For consistency with pandas methods, you should raise an ``AttributeError`` if the data passed to your accessor has an incorrect dtype. >>> pd.Series(['a', 'b']).dt Traceback (most recent call last): ... AttributeError: Can only use .dt accessor with datetimelike values Examples -------- In your library code:: import pandas as pd @pd.api.extensions.register_dataframe_accessor("geo") class GeoAccessor: def __init__(self, pandas_obj): self._obj = pandas_obj @property def center(self): # return the geographic center point of this DataFrame lat = self._obj.latitude lon = self._obj.longitude return (float(lon.mean()), float(lat.mean())) def plot(self): # plot this array's data on a map, e.g., using Cartopy pass Back in an interactive IPython session: .. code-block:: ipython In [1]: ds = pd.DataFrame({{"longitude": np.linspace(0, 10), ...: "latitude": np.linspace(0, 20)}}) In [2]: ds.geo.center Out[2]: (5.0, 10.0) In [3]: ds.geo.plot() # plots data on a map """ def decorator(accessor): if hasattr(cls, name): warnings.warn( f"registration of accessor {repr(accessor)} under name " f"{repr(name)} for type {repr(cls)} is overriding a preexisting " f"attribute with the same name.", UserWarning, stacklevel=2, ) setattr(cls, name, CachedAccessor(name, accessor)) cls._accessors.add(name) return accessor return decorator @doc(_register_accessor, klass="DataFrame") def register_dataframe_accessor(name): from pandas import DataFrame return _register_accessor(name, DataFrame) @doc(_register_accessor, klass="Series") def register_series_accessor(name): from pandas import Series return _register_accessor(name, Series) @doc(_register_accessor, klass="Index") def register_index_accessor(name): from pandas import Index return _register_accessor(name, Index)