Implement limiter

PFERD/limiter.py

@@ -0,0 +1,19 @@
+import asyncio
+from contextlib import AbstractAsyncContextManager, asynccontextmanager
+from typing import AsyncIterator
+
+
+class Limiter:
+    def __init__(self, limit: int = 10):
+        self._semaphore = asyncio.Semaphore(limit)
+
+    @asynccontextmanager
+    async def _context_manager(self) -> AsyncIterator[None]:
+        await self._semaphore.acquire()
+        try:
+            yield
+        finally:
+            self._semaphore.release()
+
+    def limit(self) -> AbstractAsyncContextManager[None]:
+        return self._context_manager()