interceptor-registry

Add pre/post/around interceptors on bound methods at runtime — without modifying the original class.

Full documentation at saemeon.github.io/interceptor-registry

Installation

pip install interceptor-registry

Quick Start

from contextlib import contextmanager
from interceptor_registry import add_interceptor, del_interceptor, del_interceptors

class Foo:
    def bar(self):
        print("inside method call")
        return "result"

    @staticmethod
    def static_bar(x):
        return x * 2

foo = Foo()

def print_before():
    print("before")

@contextmanager
def around():
    print("enter context")
    try:
        yield
    finally:
        print("exit context")

add_interceptor(foo, 'bar', print_before, callorder=-2)
add_interceptor(foo, 'bar', around, is_context_manager=True, callorder=-1)

foo.bar()
# before
# enter context
# inside method call
# exit context

# Works for instance methods, classmethods, staticmethods, async methods,
# generator methods, and async-generator methods.
add_interceptor(foo, 'static_bar', print_before, callorder=-1)

Use del_interceptor with the returned ID to remove a single interceptor, or del_interceptors to clear all:

iid = add_interceptor(foo, 'bar', print_before, callorder=-1)
del_interceptor(foo, 'bar', iid)

del_interceptors(foo, 'bar')

Not supported

• Properties and other non-callable custom descriptors (raises TypeError at registration).
• Async hook functions — async def / async-generator hooks (raises TypeError at registration).
• Async context-manager hooks (@asynccontextmanager passed with is_context_manager=True) — raises TypeError when invoked.
• Pickling of patched objects. Call del_interceptors before pickling, re-add after unpickling.

License

MIT