contextvars_quickstart_create_set_get_reset_example.py

1from contextvars import ContextVar
2
3# Declare a context variable
4var: ContextVar[str] = ContextVar('var', default='default')
5
6def main():
7    # Set a new value for the context variable in the current context
8    token = var.set('new value')
9    
10    try:
11        # Retrieve the value
12        print(var.get())  # 'new value'
13    finally:
14        # Reset the variable to the previous value
15        var.reset(token)
16
17    # After reset, it returns to the default (or previous) value
18    print(var.get())  # 'default'
19
20if __name__ == '__main__':
21    main()