Source code for

from abc import abstractmethod, ABC
from collections import OrderedDict
from contextvars import ContextVar, Token
from copy import deepcopy
from typing import List, Optional, ContextManager, Any, Tuple

from public import public

[docs]@public class Action(object): """An Action.""" inside: bool def __init__(self): self.inside = False def __enter__(self): getcontext().enter_action(self) self.inside = True return self def __exit__(self, exc_type, exc_val, exc_tb): getcontext().exit_action(self) self.inside = False
[docs]@public class Tree(OrderedDict):
[docs] def get_by_key(self, path: List) -> Any: """ Get the value in the tree at a position given by the path. :param path: The path to get. :return: The value in the tree. """ if len(path) == 0: return self value = self[path[0]] if isinstance(value, Tree): return value.get_by_key(path[1:]) elif len(path) == 1: return value else: raise ValueError
[docs] def get_by_index(self, path: List[int]) -> Tuple[Any, Any]: """ Get the key and value in the tree at a position given by the path of indices (the nodes inside a level of a tree are ordered by insertion order). :param path: The path to get. :return: The key and value. """ if len(path) == 0: raise ValueError key = list(self.keys())[path[0]] value = self[key] if len(path) == 1: return key, value elif isinstance(value, Tree): return value.get_by_index(path[1:]) else: raise ValueError
[docs] def repr(self, depth: int = 0) -> str: """ Construct a textual representation of the tree. Useful for visualization and debugging. :param depth: :return: The resulting textual representation. """ result = "" for key, value in self.items(): if isinstance(value, Tree): result += "\t" * depth + str(key) + "\n" result += value.repr(depth + 1) else: result += "\t" * depth + str(key) + ":" + str(value) + "\n" return result
def __repr__(self): return self.repr()
[docs]@public class Context(ABC): """A context is an object that traces actions which happen. There is always one context active, see functions :py:func:`getcontext`, :py:func:`setcontext` and :py:func:`resetcontext`. """
[docs] @abstractmethod def enter_action(self, action: Action) -> None: """ Enter into an action (i.e. start executing it). :param action: The action. """ ...
[docs] @abstractmethod def exit_action(self, action: Action) -> None: """ Exit from an action (i.e. stop executing it). :param action: The action. """ ...
def __str__(self): return self.__class__.__name__
[docs]@public class NullContext(Context): """A context that does not trace any actions."""
[docs] def enter_action(self, action: Action) -> None: pass
[docs] def exit_action(self, action: Action) -> None: pass
[docs]@public class DefaultContext(Context): """A context that traces executions of actions in a tree.""" actions: Tree current: List[Action]
[docs] def enter_action(self, action: Action) -> None: self.actions.get_by_key(self.current)[action] = Tree() self.current.append(action)
[docs] def exit_action(self, action: Action) -> None: if self.current[-1] != action: raise ValueError self.current.pop()
def __init__(self): self.actions = Tree() self.current = [] def __repr__(self): return f"{self.__class__.__name__}({self.actions!r}, current={self.current!r})"
_actual_context: ContextVar[Context] = ContextVar("operational_context", default=NullContext()) class _ContextManager(object): def __init__(self, new_context): self.new_context = deepcopy(new_context) def __enter__(self) -> Context: self.token = setcontext(self.new_context) return self.new_context def __exit__(self, t, v, tb): resetcontext(self.token)
[docs]@public def getcontext() -> Context: """Get the current thread/task context.""" return _actual_context.get()
[docs]@public def setcontext(ctx: Context) -> Token: """ Set the current thread/task context. :param ctx: A context to set. :return: A token to restore previous context. """ return _actual_context.set(ctx)
[docs]@public def resetcontext(token: Token): """ Reset the context to a previous value. :param token: A token to restore. """ _actual_context.reset(token)
[docs]@public def local(ctx: Optional[Context] = None) -> ContextManager: """ Use a local context. :param ctx: If none, current context is copied. :return: A context manager. """ if ctx is None: ctx = getcontext() return _ContextManager(ctx)