add some definitions to readme

boilerplates-concurrency/race_coditions.py

@@ -0,0 +1,27 @@
+#!/usr/bin/env python3
+
+import threading
+
+x = 0     
+COUNT = 10000000
+
+def foo():
+    global x
+    for i in range(COUNT):
+        x += 1
+
+def bar():
+    global x
+    for i in range(COUNT):
+        x -= 1
+
+t1 = threading.Thread(target=foo)
+t2 = threading.Thread(target=bar)
+
+t1.start()
+t2.start()
+
+t1.join()
+t2.join()
+
+print(x)