adding all files done so far

learning/singletons/client_a.py

@@ -0,0 +1,6 @@
+mygenerator = (x * x for x in range(3))
+for i in mygenerator:
+    print(i)
+
+for i in mygenerator:
+    print(i)

learning/singletons/client_b.py

@@ -0,0 +1,4 @@
+import db
+
+if (db.db_name == 'mongo'):
+    db.db_name = None

learning/singletons/db.py

@@ -0,0 +1,19 @@
+import sys
+import os
+sys.path.append(os.getcwd())    # noqa E402
+this = sys.modules[__name__]
+
+print(this)
+
+this.db_name = None
+
+print(this.db_name)
+
+
+def initialize_db(name):
+    if (this.db_name is None):
+        this.db_name = name
+        # db_name = "Local Variable"
+    else:
+        msg = f"Database is already initialized to {name}"
+        raise RuntimeError(msg.format(this.db_name))