Create username_validation.py

Author: Amogh Singhal

username_validation.py

@@ -0,0 +1,57 @@
+# Have the function UsernameValidation(`str`) take the `str` parameter being passed and determine if the string is a valid username according to the following rules:
+
+# 1. The username is between 4 and 25 characters.
+# 2. It must start with a letter.
+# 3. It can only contain letters, numbers, and the underscore character.
+# 4. It cannot end with an underscore character.
+
+#If the username is valid then your program should return the string `true`, otherwise return the string `false`.
+
+def UsernameValidation(strParam):
+
+  # username is between 4 and 25 characters
+  if len(strParam) <= 25 and len(strParam) >= 4:
+    flag1 = True
+  else:
+    flag1 = False
+
+  # start with a letter
+  if str(strParam[0]).isalpha():
+    flag2 = True
+  else:
+    flag2 = False
+
+  # contains only letters, numbers and underscore
+  valid_grammar = "abcdefghijklmnopqrstuvwxyz0123456789_"
+
+  for char in strParam:
+    if str(char).isalpha() == False:
+      if char in valid_grammar:
+        flag3 = True
+      else:
+        flag3 = False
+
+    else:
+      if str.lower(char) in valid_grammar:
+        flag3 = True
+      else:
+        flag3 = False    
+
+
+  # can't end with an underscore
+  if str(strParam[-1]) != '_':
+    flag4 = True
+  else:
+    flag4 = False
+
+  final_output = flag1 and flag2 and flag3 and flag4
+
+  # code goes here
+  return final_output
+
+# keep this function call here
+TC1 = "aa_"
+TC2 = "u__hello_world123"
+
+print(TC1, UsernameValidation(TC1))
+print(TC2, UsernameValidation(TC2))