add re_demo3.py

Author: yennanliu

regular_expression/re_demo3.py

@@ -0,0 +1,8 @@
+import re
+
+# https://regex101.com/
+pattern = re.compile(r"[A-Za-z0-9$%#@]{7,}[0-9]")
+mystring = 'accd1234'
+
+a = pattern.fullmatch(mystring)
+print (a)