databricks.koalas.extensions.register_index_accessor¶
-
databricks.koalas.extensions.
register_index_accessor
(name)[source]¶ Register a custom accessor with an Index
- Parameters
- namestr
name used when calling the accessor after its registered
- 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
Notes
When accessed, your accessor will be initialiazed with the Koalas object the user is interacting with. The code signature must be:
def __init__(self, koalas_obj): # constructor logic ...
In the pandas API, if data passed to your accessor has an incorrect dtype, it’s recommended to raise an
AttributeError
for consistency purposes. In Koalas,ValueError
is more frequently used to annotate when a value’s datatype is unexpected for a given method/function.Ultimately, you can structure this however you like, but Koalas would likely do something like this:
>>> ks.Series(['a', 'b']).dt ... Traceback (most recent call last): ... ValueError: Cannot call DatetimeMethods on type StringType
Examples
In your library code:
from databricks.koalas.extensions import register_index_accessor @register_index_accessor("foo") class CustomAccessor: def __init__(self, koalas_obj): self._obj = koalas_obj self.item = "baz" @property def bar(self): # return item value return self.item
Then, in an ipython session:
>>> ## Import if the accessor is in the other file. >>> # from my_ext_lib import CustomAccessor >>> kdf = ks.DataFrame({"longitude": np.linspace(0,10), ... "latitude": np.linspace(0, 20)}) >>> kdf.index.foo.bar 'baz'