Python 3.7+contextvarsterm

contextvars

module

Context variables: a value of its own for each asynchronous task and each context.

Syntax

import contextvars

Use it when asynchronous code needs something like a global variable — a request id, the current user — that does not leak between tasks. threading.local does not work for this: all coroutines in one thread share its value. Change the value with set and roll it back with reset using the returned token; each asyncio task gets a copy of the context.

Examples

import contextvars
user = contextvars.ContextVar('user', default='гость')
token = user.set('Аня')
print(user.get())  # → Аня
user.reset(token)
print(user.get())  # → гость

See also

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