Is it possible to implement a custom context manager in Python without using built-in tools?

Yes, it is possible to implement a custom context manager in Python without using built-in features (with and __enter__/__exit__ methods). You can create a class with methods for explicit resource management, such as start() and stop(), and use them manually.

Example:

class MyContextManager:
    def __init__(self):
        self.resource = None

    def start(self):
        print("Resource opened")
        self.resource = "Active resource"

    def stop(self):
        print("Resource closed")
        self.resource = None

# Usage
mgr = MyContextManager()
mgr.start()
# work with the resource
print(mgr.resource)
mgr.stop()

This way, you manually control the resource's lifecycle, but do not use the with syntax. However, the built-in context manager is more convenient and safer, as it guarantees resource release even in case of exceptions.