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