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"""Register functions as methods of Pandas DataFrame and Series."""
from __future__ import annotations
import warnings
from functools import wraps
from pandas.core.groupby.generic import DataFrameGroupBy
from pandas.util._exceptions import find_stack_level
from pandas.api.extensions import (
register_series_accessor,
register_dataframe_accessor,
)
import inspect
method_call_ctx_factory = None
def handle_pandas_extension_call(method, method_signature, obj, args, kwargs):
"""Handle pandas extension call.
This function is called when the user calls
a pandas DataFrame object's method.
The pandas extension mechanism passes args and kwargs
of the original method call as it is applied to obj.
Our implementation uses the global variable `method_call_ctx_factory`.
`method_call_ctx_factory` can be either None or an abstract class.
When `method_call_ctx_factory` is None,
the implementation calls the registered method
with unmodified args and kwargs and returns underlying method result.
When `method_call_ctx_factory` is not None,
`method_call_ctx_factory` is expected to refer to
the function to create the context object.
The context object will be used to process
inputs and outputs of `method` calls.
It is also possible that
the context object method `handle_start_method_call`
will modify original args and kwargs before `method` call.
`method_call_ctx_factory` is a function
that should have the following signature:
`f(method_name: str, args: list, kwargs: dict) -> MethodCallCtx`
MethodCallCtx is an abstract class:
class MethodCallCtx(abc.ABC):
@abstractmethod
def __enter__(self) -> None:
raise NotImplemented
@abstractmethod
def __exit__(self, exc_type, exc_value, traceback) -> None:
raise NotImplemented
@abstractmethod
def handle_start_method_call(self, method_name: str, method_signature: inspect.Signature, method_args: list, method_kwargs: dict) -> tuple(list, dict):
raise NotImplemented
@abstractmethod
def handle_end_method_call(self, ret: object) -> None:
raise NotImplemented
Args:
method (callable): method object as registered by decorator
register_dataframe_method (or register_series_method)
method_signature: signature of method as returned by inspect.signature
obj: Dataframe or Series
args: The arguments to pass to the registered method.
kwargs: The keyword arguments to pass to the registered method.
Returns:
object`: The result of calling of the method.
""" # noqa: E501
global method_call_ctx_factory
with method_call_ctx_factory(
method.__name__, args, kwargs
) as method_call_ctx:
if method_call_ctx is None: # nullcontext __enter__ returns None
ret = method(obj, *args, **kwargs)
else:
all_args = tuple([obj] + list(args))
(
new_args,
new_kwargs,
) = method_call_ctx.handle_start_method_call(
method.__name__, method_signature, all_args, kwargs
)
args = new_args[1:]
kwargs = new_kwargs
ret = method(obj, *args, **kwargs)
method_call_ctx.handle_end_method_call(ret)
return ret
def register_dataframe_method(method):
"""Register a function as a method attached to the Pandas DataFrame.
Example:
@register_dataframe_method
def print_column(df, col):
'''Print the dataframe column given'''
print(df[col])
Args:
method (callable): callable to register as a dataframe method.
Returns:
callable: The original method.
"""
method_signature = inspect.signature(method)
def inner(*args, **kwargs):
"""Inner function to register the method.
This function is called when the user
decorates a function with register_dataframe_method.
Args:
*args: The arguments to pass to the registered method.
**kwargs: The keyword arguments to pass to the registered method.
Returns:
method: The original method.
"""
class AccessorMethod(object):
"""DataFrame Accessor method class."""
def __init__(self, pandas_obj):
"""Initialize the accessor method class.
Args:
pandas_obj (pandas.DataFrame): The pandas DataFrame object.
"""
self._obj = pandas_obj
@wraps(method)
def __call__(self, *args, **kwargs):
"""Call the accessor method.
Args:
*args: The arguments to pass to the registered method.
**kwargs: The keyword arguments to pass
to the registered method.
Returns:
object: The result of calling of the method.
"""
global method_call_ctx_factory
if method_call_ctx_factory is None:
return method(self._obj, *args, **kwargs)
return handle_pandas_extension_call(
method, method_signature, self._obj, args, kwargs
)
register_dataframe_accessor(method.__name__)(AccessorMethod)
return method
return inner()
def register_series_method(method):
"""Register a function as a method attached to the Pandas Series.
Args:
method (callable): callable to register as a series method.
Returns:
callable: The original method.
"""
method_signature = inspect.signature(method)
def inner(*args, **kwargs):
"""Inner function to register the method.
Args:
*args: The arguments to pass to the registered method.
**kwargs: The keyword arguments to pass to the registered method.
Returns:
method: The original method.
"""
class AccessorMethod(object):
"""Series Accessor method class."""
__doc__ = method.__doc__
def __init__(self, pandas_obj):
"""Initialize the accessor method class.
Args:
pandas_obj (pandas.Series): The pandas Series object.
"""
self._obj = pandas_obj
@wraps(method)
def __call__(self, *args, **kwargs):
"""Call the accessor method.
Args:
*args: The arguments to pass to the registered method.
**kwargs: The keyword arguments to pass
to the registered method.
Returns:
object: The result of calling of the method.
"""
global method_call_ctx_factory
if method_call_ctx_factory is None:
return method(self._obj, *args, **kwargs)
return handle_pandas_extension_call(
method, method_signature, self._obj, args, kwargs
)
register_series_accessor(method.__name__)(AccessorMethod)
return method
return inner()
# variant of pandas' accessor
# copied from pandas' accessor file - pandas/pandas/core/accessor.py
"""
accessor.py contains base classes for implementing accessor properties
that can be mixed into or pinned onto other pandas classes.
"""
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 : DataFrameGroupBy
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: DataFrameGroupBy) -> 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
def _register_accessor(name: str, cls: DataFrameGroupBy):
"""
Register a custom accessor on a DataFrameGroupBy object.
Args:
name : str
Name under which the accessor should be registered.
A warning is issued
if this name conflicts with a preexisting attribute.
cls: DataFrameGroupBy
Returns:
A class decorator.
"""
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=find_stack_level(),
)
setattr(cls, name, CachedAccessor(name, accessor))
if not hasattr(cls, "_accessors"):
cls._accessors = set()
cls._accessors.add(name)
return accessor
return decorator
def register_groupby_accessor(name: str):
return _register_accessor(name, DataFrameGroupBy)
def register_groupby_method(method):
"""Register a function as a method attached to the pandas DataFrameGroupBy.
Example:
>>> @register_groupby_method # doctest: +SKIP
>>> def print_column(grp, col): # doctest: +SKIP
... '''Print the dataframe column given''' # doctest: +SKIP
... print(grp[col]) # doctest: +SKIP
!!! info "New in version 0.7.0"
Args:
method: Function to be registered as a method
on the DataFrameGroupBy object.
Returns:
callable: The original method.
"""
method_signature = inspect.signature(method)
def inner(*args: tuple, **kwargs: dict):
"""Inner function to register the method.
This function is called when the user
decorates a function with register_groupby_method.
Args:
*args: The arguments to pass to the registered method.
**kwargs: The keyword arguments to pass to the registered method.
Returns:
method: The original method.
"""
class AccessorMethod(object):
"""DataFrameGroupBy Accessor method class."""
__doc__ = method.__doc__
def __init__(self, obj):
"""Initialize the accessor method class.
Args:
obj: The pandas DataFrameGroupBy object.
"""
self._obj = obj
@wraps(method)
def __call__(self, *args, **kwargs):
"""Call the accessor method.
Args:
*args: The arguments to pass to the registered method.
**kwargs: The keyword arguments to pass
to the registered method.
Returns:
object: The result of calling of the method.
"""
global method_call_ctx_factory
if method_call_ctx_factory is None:
return method(self._obj, *args, **kwargs)
return handle_pandas_extension_call(
method, method_signature, self._obj, args, kwargs
)
register_groupby_accessor(method.__name__)(AccessorMethod)
return method
return inner()
|
