Use scandir to save memory

src/watchdog/observers/polling.py

@@ -58,6 +58,11 @@
     FileModifiedEvent
 )
 
+try:
+    from os import scandir
+except ImportError:
+    from os import listdir as scandir
+
 
 class PollingEmitter(EventEmitter):
     """
@@ -66,7 +71,7 @@ class PollingEmitter(EventEmitter):
     """
 
     def __init__(self, event_queue, watch, timeout=DEFAULT_EMITTER_TIMEOUT,
-                 stat=default_stat, listdir=os.listdir):
+                 stat=default_stat, listdir=scandir):
         EventEmitter.__init__(self, event_queue, watch, timeout)
         self._snapshot = None
         self._lock = threading.Lock()

src/watchdog/utils/dirsnapshot.py

@@ -48,6 +48,10 @@
 import os
 from stat import S_ISDIR
 from watchdog.utils import stat as default_stat
+try:
+    from os import scandir
+except ImportError:
+    from os import listdir as scandir
 
 
 class DirectorySnapshotDiff(object):
@@ -199,7 +203,7 @@ class DirectorySnapshot(object):
     def __init__(self, path, recursive=True,
                  walker_callback=(lambda p, s: None),
                  stat=default_stat,
-                 listdir=os.listdir):
+                 listdir=scandir):
         self._stat_info = {}
         self._inode_to_path = {}
 
@@ -209,7 +213,8 @@ def __init__(self, path, recursive=True,
 
         def walk(root):
             try:
-                paths = [os.path.join(root, name) for name in listdir(root)]
+                paths = [os.path.join(root, entry if isinstance(entry, str) else entry.name)
+                         for entry in listdir(root)]
             except OSError as e:
                 # Directory may have been deleted between finding it in the directory
                 # list of its parent and trying to delete its contents. If this