allow to set timeout and maxsize; fixed a weird conditional

bstrd/bscache.py

@@ -6,10 +6,11 @@ from .prodthread import ProdThread
 
 class BSCache:
 
-    def __init__(self):
+    def __init__(self, timeout=1000, maxsize=100):
+        self.timeout = timeout
         self.channels = {}
         self.data = None
-        self.pt = ProdThread(self.run)
+        self.pt = ProdThread(self.run, maxsize=maxsize)
 
     def __repr__(self):
         return str(self.data)
@@ -26,9 +27,11 @@ class BSCache:
 
     def run(self, running):
         configs = self.channels.values()
-        with source(channels=configs, receive_timeout=-1) as src:
+        with source(channels=configs, receive_timeout=self.timeout) as src:
             while running.is_set():
                 msg = src.receive()
+                if msg is None:
+                    continue
                 data = repack(msg)
                 if data:
                     yield data
@@ -39,7 +42,7 @@ class BSCache:
 
 
     def get_var(self, name, modulo=None, offset=None):
-        if name is not "pid" and not name in self.channels:
+        if name != "pid" and name not in self.channels:
             if not is_available(name):
                 raise ValueError(f"channel {name} is not available")
             cfg = make_channel_config(name, modulo, offset)