234 lines
6.8 KiB
Python
234 lines
6.8 KiB
Python
# -*- coding: utf-8 -*-
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#
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# Author: Krishna Sunkara (kpsunkara)
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#
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# Re-entrant, reusable context manager to store execution context. Introduced
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# in pmdarima 1.5.0 (see #221), redesigned not to use thread locals in #273
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# (see #275 for context).
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from abc import ABC, abstractmethod
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from enum import Enum
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import collections
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__all__ = ['AbstractContext', 'ContextStore', 'ContextType']
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class _CtxSingleton:
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"""Singleton class to store context information"""
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store = {}
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_ctx = _CtxSingleton()
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class ContextType(Enum):
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"""Context Type Enumeration
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An enumeration of Context Types known to :class:`ContextStore`
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"""
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EMPTY = 0
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STEPWISE = 1
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class AbstractContext(ABC):
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"""An abstract context manager to store execution context.
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A generic, re-entrant, reusable context manager to store
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execution context. Has helper methods to iterate over the context info
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and provide a string representation of the context info.
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"""
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def __init__(self, **kwargs):
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# remove None valued entries,
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# since __getattr__ returns None if an attr is not present
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self.props = {k: v for k, v in kwargs.items() if v is not None} \
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if kwargs else {}
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def __enter__(self):
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ContextStore._add_context(self)
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def __exit__(self, exc_type, exc_val, exc_tb):
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ContextStore._remove_context(self)
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def __getattr__(self, item):
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"""Lets us access, e.g., ``ctx.max_steps`` even if not in a context"""
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return self.props[item] if item in self.props else None
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def __contains__(self, item):
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return item in self.props
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def __getitem__(self, item):
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return self.props[item] if item in self.props else None
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def __iter__(self):
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return iter(self.props)
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def keys(self):
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return self.props.keys()
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def values(self):
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return self.props.values()
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def items(self):
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return self.props.items()
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def update(self, other):
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parent_props = dict(other)
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parent_props.update(self.props)
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self.props = parent_props
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def __repr__(self):
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return self.props.__repr__()
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@abstractmethod
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def get_type(self):
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"""Get the ContextType"""
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class _emptyContext(AbstractContext):
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"""An empty context for convenience use"""
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def __init__(self):
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super(_emptyContext, self).__init__()
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def get_type(self):
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"""Indicates we are not in a context manager"""
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return ContextType.EMPTY
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class ContextStore:
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"""A class to wrap access to the global context store
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This class hosts static methods to wrap access to and encapsulate the
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singleton content store instance
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"""
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@staticmethod
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def get_context(context_type):
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"""Returns most recently added instance of given Context Type
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Parameters
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----------
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context_type : ContextType
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Context type to retrieve from the store
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Returns
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-------
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res : AbstractContext
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An instance of AbstractContext subclass or None
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"""
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if not isinstance(context_type, ContextType):
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raise ValueError('context_type must be an instance of ContextType')
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if context_type in _ctx.store and len(_ctx.store[context_type]) > 0:
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return _ctx.store[context_type][-1]
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# If not present
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return None
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@staticmethod
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def get_or_default(context_type, default):
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"""Returns most recent instance of given Context Type or default
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Parameters
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----------
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context_type : ContextType
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Context type to retrieve from the store
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default : AbstractContext
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Value to return in case given context does not exist
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Returns
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-------
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ctx : AbstractContext
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An instance of AbstractContext subclass or default
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"""
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ctx = ContextStore.get_context(context_type)
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return ctx if ctx else default
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@staticmethod
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def get_or_empty(context_type):
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"""Returns recent instance of given Context Type or an empty context
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Parameters
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----------
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context_type : ContextType
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Context type to retrieve from the store
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Returns
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-------
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res : AbstractContext
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An instance of AbstractContext subclass
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"""
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return ContextStore.get_or_default(context_type, _emptyContext())
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@staticmethod
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def _add_context(ctx):
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"""Add given instance of AbstractContext subclass to context store
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This private member is only called by ``AbstractContext.__init__()``
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if the given ctx is nested, merge parent context, to support
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following usage:
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Examples
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--------
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>>> from pmdarima.arima import StepwiseContext, auto_arima
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>>> with StepwiseContext(max_steps=10):
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... with StepwiseContext(max_dur=30):
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... auto_arima(samp,...)
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This is identical to:
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>>> from contextlib import ExitStack
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... stack = ExitStack()
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... outer_ctx = StepwiseContext(max_steps=10)
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... inner_ctx = StepwiseContext(max_dur=30)
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... stack.enter_context(outer_ctx)
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... stack.enter_context(inner_ctx)
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... with stack:
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... auto_arima(samp, ...)
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However, the nested context can override parent context. In the
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example below, the effective context for inner most call to
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``auto_arima(...)`` is: ``max_steps=15, max_dur=30``. The effective
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context for the second call to ``auto_arima(..)`` is: ``max_steps=10``
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>>> with StepwiseContext(max_steps=10):
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... with StepwiseContext(max_steps=15, max_dur=30):
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... auto_arima(samp,...)
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...
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... auto_arima(samp,...)
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"""
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if not isinstance(ctx, AbstractContext):
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raise ValueError('ctx must be be an instance of AbstractContext')
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# if given Context Type is not present into store, make an entry
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context_type = ctx.get_type()
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if context_type not in _ctx.store:
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_ctx.store[context_type] = collections.deque()
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# if the context is nested, merge with parent's context
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if len(_ctx.store[context_type]) > 0:
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parent = _ctx.store[context_type][-1]
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ctx.update(parent)
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_ctx.store[context_type].append(ctx)
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@staticmethod
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def _remove_context(ctx):
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"""Removes the most recently added context of given Context Type
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This private member is only used by ``AbstractContext``
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:param ctx:
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:return: None
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"""
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if not isinstance(ctx, AbstractContext):
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raise ValueError('ctx must be be an instance of AbstractContext')
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context_type = ctx.get_type()
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if context_type not in _ctx.store or \
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len(_ctx.store[context_type]) == 0:
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return
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_ctx.store[context_type].pop()
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