python (3.12.0)
1 import enum
2
3 from types import TracebackType
4 from typing import final, Optional, Type
5
6 from . import events
7 from . import exceptions
8 from . import tasks
9
10
11 __all__ = (
12 "Timeout",
13 "timeout",
14 "timeout_at",
15 )
16
17
18 class ESC[4;38;5;81m_State(ESC[4;38;5;149menumESC[4;38;5;149m.ESC[4;38;5;149mEnum):
19 CREATED = "created"
20 ENTERED = "active"
21 EXPIRING = "expiring"
22 EXPIRED = "expired"
23 EXITED = "finished"
24
25
26 @final
27 class ESC[4;38;5;81mTimeout:
28 """Asynchronous context manager for cancelling overdue coroutines.
29
30 Use `timeout()` or `timeout_at()` rather than instantiating this class directly.
31 """
32
33 def __init__(self, when: Optional[float]) -> None:
34 """Schedule a timeout that will trigger at a given loop time.
35
36 - If `when` is `None`, the timeout will never trigger.
37 - If `when < loop.time()`, the timeout will trigger on the next
38 iteration of the event loop.
39 """
40 self._state = _State.CREATED
41
42 self._timeout_handler: Optional[events.TimerHandle] = None
43 self._task: Optional[tasks.Task] = None
44 self._when = when
45
46 def when(self) -> Optional[float]:
47 """Return the current deadline."""
48 return self._when
49
50 def reschedule(self, when: Optional[float]) -> None:
51 """Reschedule the timeout."""
52 assert self._state is not _State.CREATED
53 if self._state is not _State.ENTERED:
54 raise RuntimeError(
55 f"Cannot change state of {self._state.value} Timeout",
56 )
57
58 self._when = when
59
60 if self._timeout_handler is not None:
61 self._timeout_handler.cancel()
62
63 if when is None:
64 self._timeout_handler = None
65 else:
66 loop = events.get_running_loop()
67 if when <= loop.time():
68 self._timeout_handler = loop.call_soon(self._on_timeout)
69 else:
70 self._timeout_handler = loop.call_at(when, self._on_timeout)
71
72 def expired(self) -> bool:
73 """Is timeout expired during execution?"""
74 return self._state in (_State.EXPIRING, _State.EXPIRED)
75
76 def __repr__(self) -> str:
77 info = ['']
78 if self._state is _State.ENTERED:
79 when = round(self._when, 3) if self._when is not None else None
80 info.append(f"when={when}")
81 info_str = ' '.join(info)
82 return f"<Timeout [{self._state.value}]{info_str}>"
83
84 async def __aenter__(self) -> "Timeout":
85 self._state = _State.ENTERED
86 self._task = tasks.current_task()
87 self._cancelling = self._task.cancelling()
88 if self._task is None:
89 raise RuntimeError("Timeout should be used inside a task")
90 self.reschedule(self._when)
91 return self
92
93 async def __aexit__(
94 self,
95 exc_type: Optional[Type[BaseException]],
96 exc_val: Optional[BaseException],
97 exc_tb: Optional[TracebackType],
98 ) -> Optional[bool]:
99 assert self._state in (_State.ENTERED, _State.EXPIRING)
100
101 if self._timeout_handler is not None:
102 self._timeout_handler.cancel()
103 self._timeout_handler = None
104
105 if self._state is _State.EXPIRING:
106 self._state = _State.EXPIRED
107
108 if self._task.uncancel() <= self._cancelling and exc_type is exceptions.CancelledError:
109 # Since there are no new cancel requests, we're
110 # handling this.
111 raise TimeoutError from exc_val
112 elif self._state is _State.ENTERED:
113 self._state = _State.EXITED
114
115 return None
116
117 def _on_timeout(self) -> None:
118 assert self._state is _State.ENTERED
119 self._task.cancel()
120 self._state = _State.EXPIRING
121 # drop the reference early
122 self._timeout_handler = None
123
124
125 def timeout(delay: Optional[float]) -> Timeout:
126 """Timeout async context manager.
127
128 Useful in cases when you want to apply timeout logic around block
129 of code or in cases when asyncio.wait_for is not suitable. For example:
130
131 >>> async with asyncio.timeout(10): # 10 seconds timeout
132 ... await long_running_task()
133
134
135 delay - value in seconds or None to disable timeout logic
136
137 long_running_task() is interrupted by raising asyncio.CancelledError,
138 the top-most affected timeout() context manager converts CancelledError
139 into TimeoutError.
140 """
141 loop = events.get_running_loop()
142 return Timeout(loop.time() + delay if delay is not None else None)
143
144
145 def timeout_at(when: Optional[float]) -> Timeout:
146 """Schedule the timeout at absolute time.
147
148 Like timeout() but argument gives absolute time in the same clock system
149 as loop.time().
150
151 Please note: it is not POSIX time but a time with
152 undefined starting base, e.g. the time of the system power on.
153
154 >>> async with asyncio.timeout_at(loop.time() + 10):
155 ... await long_running_task()
156
157
158 when - a deadline when timeout occurs or None to disable timeout logic
159
160 long_running_task() is interrupted by raising asyncio.CancelledError,
161 the top-most affected timeout() context manager converts CancelledError
162 into TimeoutError.
163 """
164 return Timeout(when)
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