Attribut error when using contextvar in python 3.10

Question

When running this code below I got an

AttributError: __enter__

I looked around with no success.

import contextvars

# Création d'une variable de contexte
user_context = contextvars.ContextVar("user")

# Définition de la valeur de la variable dans le contexte actuel
with user_context.set("utilisateur123"):
    # Cette valeur est accessible à l'intérieur de ce bloc
    print(user_context.get())  # Affiche "utilisateur123"

# En dehors du bloc, la valeur redevient celle par défaut (None)
print(user_context.get())  # Affiche "None"

Show the full traceback of the error as properly formatted text (formatted as code) in the question. — Michael Butscher
– Michael Butscher, Commented Nov 10, 2023 at 16:39
A context variable is not a context manager, you can't use it with with. — Barmar
– Barmar, Commented Nov 10, 2023 at 16:49

jsbueno · Accepted Answer · 2023-11-23 00:04:05Z

You are probably confusing the two uses of the word "context" here - the fact is that contextvars, as provided in the module with that name, do not work as Python contexts - the type of objects that work in the with statement. (Although such an interface would make sense, and I do implement it in my personal, unfinished, project at https://github.com/jsbueno/extracontext )

The correct way to execute some code in a separate context, is by containing it in a function and call it by using the .run() method in a context:


import contextvars

# Création d'une variable de contexte
user_context = contextvars.ContextVar("user")

def my_code():
    """this function will run in an independent copy of the outter context"""
    # Définition de la valeur de la variable dans le contexte actuel
    user_context.set("utilisateur123"):
    # Cette valeur est accessible à l'intérieur de ce bloc
    print(user_context.get())  # Affiche "utilisateur123"

my_context = contextvars.copy_context()
my_context.run(my_code)

# En dehors du bloc, la valeur redevient celle par défaut (None)
print(user_context.get())  # Affiche "None"

Collectives™ on Stack Overflow

Attribut error when using contextvar in python 3.10

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related