exceptions added for user input

exceptions.py

@@ -0,0 +1,22 @@
+class NotANumberException(Exception):
+    pass
+
+
+class SubjectNotExistingException(Exception):
+    pass
+
+
+class CategoryNotExistingException(Exception):
+    pass
+
+
+class WrongCaseException(Exception):
+    pass
+
+
+def convertible(string):
+    try:
+        float(string)
+        return True
+    except ValueError:
+        raise NotANumberException

main.py

@@ -2,6 +2,7 @@ import subject
 import user_IO
 import serializer
 import encryption
+import exceptions
 import os
 
 subjects = []
@@ -13,9 +14,8 @@ try:
             string = encryption.decrypt(password, file.read())
             serializer.deserialize(string)
 
-
-
     while True:
+        try:
             user_input = user_IO.user_input()
             input_or_output = user_input[0]
             if input_or_output == "input":
@@ -38,12 +38,21 @@ try:
                     _main = user_input[3]
                     _oral = user_input[4]
                     subjects.append(subject.Subject(_subject, _main, _oral))
+                else:
+                    raise exceptions.WrongCaseException
             elif input_or_output == "output":
                 _subject = user_input[1]
                 subject_get = subject.get_subject(subjects, _subject)
                 user_IO.user_output(subject_get.return_average_subject)
             elif input_or_output == "exit":
                 break
+            else:
+                raise exceptions.WrongCaseException
+
+        except (exceptions.NotANumberException, exceptions.CategoryNotExistingException,
+                exceptions.SubjectNotExistingException, exceptions.WrongCaseException) as e:
+            user_IO.exception_raised(e)
+
     with open(filepath, 'w') as file:
         _list = [serializer.serialize(_subject) for _subject in subjects]
         string = encryption.encrypt(password, str(_list))

subject.py

@@ -1,4 +1,5 @@
 from datetime import datetime as str_date
+from exceptions import SubjectNotExistingException, CategoryNotExistingException
 
 
 class Subject:
@@ -31,6 +32,11 @@ class Subject:
             grade_sum += self.return_average_of_category(i)
         return grade_sum / rating_sum
 
+    def category_existing(self, category):
+        if category in self.grades:
+            return True
+        raise CategoryNotExistingException
+
 
 class Grade:
     def __init__(self, grade, name, date=str(str_date.now())):
@@ -43,4 +49,4 @@ def get_subject(liste, name):
     for subject in liste:
         if subject.name == name:
             return subject
-    return None
+    raise SubjectNotExistingException

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":
@@ -14,22 +17,28 @@ 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"))
+            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")
+            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")