with-contextvars 0.1.0

Context manager for setting contextvars variables

This module provides Set, a context manager which sets one or more contextvars variables upon activation and resets them to their previous values at exit.

Usage:

import contextvars, with_contextvars
A = contextvars.ContextVar("A")
B = contextvars.ContextVar("B")
A.set("Hello,")
B.set("world!")
print(A.get(), B.get())
# prints: Hello, world!
with with_contextvars.Set((A, "other"), (B, "value")):
    print(A.get(), B.get())
    # prints: other value
print(A.get(), B.get())
# prints: Hello, world!

Even the entirety of variable assignments of a contextvars.Context object (as obtained from contextvars.copy_context()) can be activated by initializing Set with its items:

with with_contextvars.Set(*context.items()):
    ...

However, using contextvars.Context.run() is more efficient and should be preferred where possible.

More information can be found in the documentation of Set.