started main and fixed issue #7

main.py

@@ -0,0 +1,11 @@
+import subject
+import user_IO
+
+subjects = []
+while True:
+    user_input = user_IO.user_input()
+    if user_input[0] == "input":
+        if user_input[1] == "grade":
+            subject_edit = subject.get_subject(subjects, user_input[2])
+            if subject_edit:
+                subject_edit.add_grade(user_input[3], subject.Grade(user_input[4], user_input[5]))

subject.py

@@ -26,3 +26,10 @@ class Grade:
         self.grade = grade
         self.name = name
         self.date = date
+
+
+def get_subject(liste, name):
+    for subject in liste:
+        if subject.name == name:
+            return subject
+    return None

user_IO.py

@@ -10,15 +10,15 @@ def user_input():
         user_add = input()
         if user_add == "subject":
             subject = input("Which subject do you want to add? \n")
-            return "input", subject
+            return "input", "subject", subject
         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", subject, category, 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", subject, category, grade, grade_name
+            return "input", "grade", subject, category, grade, grade_name