exceptions added for user input

user_IO.py

@@ -1,3 +1,6 @@
+import exceptions
+
+
 def user_input():
     todo = input("Ok, do you want to see them or to edit them [see/edit/exit]?\n")
     if todo == "see":
@@ -14,23 +17,29 @@ def user_input():
                 main_subject = True
             elif main_subject == 'n':
                 main_subject = False
+            else:
+                raise exceptions.WrongCaseException
             oral_exam = input("Will there be an oral exam in this subject [y/n]? \n")
             if oral_exam == 'y':
                 oral_exam = True
             elif oral_exam == 'n':
                 oral_exam = False
+            else:
+                raise exceptions.WrongCaseException
             return "input", "subject", subject, main_subject, oral_exam
         elif user_add == "category":
             subject = input("To which subject do you want to add the category? \n")
             category = input("Which category do you want to add? \n")
             rating = float(input("Rating? \n"))
-            return "input", "category", subject, category, rating
+            if exceptions.convertible(rating):
+                return "input", "category", subject, category, rating
         elif user_add == "grade":
             subject = input("To which subject do you want to add the grade? \n")
             category = input("To which category do you want to add it? \n")
             grade = input("Grade? \n")
             grade_name = input("What's the name of the grade? \n")
-            return "input", "grade", subject, category, grade, grade_name
+            if exceptions.convertible(grade):
+                return "input", "grade", subject, category, grade, grade_name
     elif todo == "exit":
         return "exit"
 
@@ -49,3 +58,15 @@ def user_output(subject, categories, average, average_subject):
 def password():
     print("What is your password?")
     return input()
+
+
+def exception_raised(exception):
+    print("Dear user you've raised an exception. The cause of the exception is:")
+    if exception is exceptions.SubjectNotExistingException:
+        print("The subject you tried to access is not created")
+    elif exceptions is exceptions.CategoryNotExistingException:
+        print("The category you tried to add something is non-existent in this subject")
+    elif exception is exceptions.NotANumberException:
+        print("The number you gave the program is not a number")
+    elif exception is exceptions.WrongCaseException:
+        print("This was not one of the available choices")