Use context managers for threading.Lock()

(zzzeek:) For some reason I thought that threading.Lock() still did
not support context managers, at least in Python 2, however this
does not seem to be the case.

Co-authored-by: Mike Bayer <mike_mp@zzzcomputing.com>
Closes: #5069
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/5069
Pull-request-sha: efeac06dda5afdbe33abcf9b27c8b5b5725c8444

Change-Id: Ic64fcd99cd587bc70b4ecc5b45d8205b5c76eff2

2 files changed, 11 insertions, 28 deletions

diff --git a/lib/sqlalchemy/util/langhelpers.py b/lib/sqlalchemy/util/langhelpers.py
index 83f119660..8124764be 100644
--- a/lib/sqlalchemy/util/langhelpers.py
+++ b/lib/sqlalchemy/util/langhelpers.py
@@ -1179,11 +1179,8 @@ def counter():
 
     # avoid the 2to3 "next" transformation...
     def _next():
-        lock.acquire()
-        try:
+        with lock:
             return next(counter)
-        finally:
-            lock.release()
 
     return _next
 
@@ -1362,14 +1359,11 @@ class symbol(object):
     _lock = compat.threading.Lock()
 
     def __new__(cls, name, doc=None, canonical=None):
-        cls._lock.acquire()
-        try:
+        with cls._lock:
             sym = cls.symbols.get(name)
             if sym is None:
                 cls.symbols[name] = sym = _symbol(name, doc, canonical)
             return sym
-        finally:
-            symbol._lock.release()
 
     @classmethod
     def parse_user_argument(
diff --git a/lib/sqlalchemy/util/queue.py b/lib/sqlalchemy/util/queue.py
index 819d95684..78b7351d4 100644
--- a/lib/sqlalchemy/util/queue.py
+++ b/lib/sqlalchemy/util/queue.py
@@ -66,28 +66,22 @@ class Queue:
     def qsize(self):
         """Return the approximate size of the queue (not reliable!)."""
 
-        self.mutex.acquire()
-        n = self._qsize()
-        self.mutex.release()
-        return n
+        with self.mutex:
+            return self._qsize()
 
     def empty(self):
         """Return True if the queue is empty, False otherwise (not
         reliable!)."""
 
-        self.mutex.acquire()
-        n = self._empty()
-        self.mutex.release()
-        return n
+        with self.mutex:
+            return self._empty()
 
     def full(self):
         """Return True if the queue is full, False otherwise (not
         reliable!)."""
 
-        self.mutex.acquire()
-        n = self._full()
-        self.mutex.release()
-        return n
+        with self.mutex:
+            return self._full()
 
     def put(self, item, block=True, timeout=None):
         """Put an item into the queue.
@@ -102,8 +96,7 @@ class Queue:
         (`timeout` is ignored in that case).
         """
 
-        self.not_full.acquire()
-        try:
+        with self.not_full:
             if not block:
                 if self._full():
                     raise Full
@@ -121,8 +114,6 @@ class Queue:
                     self.not_full.wait(remaining)
             self._put(item)
             self.not_empty.notify()
-        finally:
-            self.not_full.release()
 
     def put_nowait(self, item):
         """Put an item into the queue without blocking.
@@ -142,9 +133,9 @@ class Queue:
         available within that time.  Otherwise (`block` is false),
         return an item if one is immediately available, else raise the
         ``Empty`` exception (`timeout` is ignored in that case).
+
         """
-        self.not_empty.acquire()
-        try:
+        with self.not_empty:
             if not block:
                 if self._empty():
                     raise Empty
@@ -163,8 +154,6 @@ class Queue:
             item = self._get()
             self.not_full.notify()
             return item
-        finally:
-            self.not_empty.release()
 
     def get_nowait(self):
         """Remove and return an item from the queue without blocking.