add re ref (README.md)

Author: yennanliu

README.md

@@ -23,7 +23,13 @@
 
 ### Ref 
 
+- Regular expression doc 
+	- https://www.w3schools.com/python/python_regex.asp
+
+- Regular expression online playground 
+	- https://regex101.com/
+
 - Unit test mock DB func with python 
 	- https://www.stevenmaude.co.uk/posts/how-to-use-mock-in-python-to-mock?fbclid=IwAR15w5IZesgbksFYkp_HBxMXRVk2ip1LMnZ6J3Jf4_LjXuaQLPzCNk1x_58
 	- https://stackoverflow.com/questions/58873971/python-mock-multiple-queries-in-a-function-using-pytest-mock?fbclid=IwAR3Ouw0im_iFT6PBIclw5lLwNXs3lCTfayQdmZdYfYEpoFyLDmzHVMnf6zQ
-	- 
+	

regular_expression/README.md

@@ -0,0 +1,4 @@
+## Regular_Expression
+
+## Ref
+- https://www.w3schools.com/python/python_regex.asp