title: Merge three dictionaries in Python
body: <p>I am trying to merge three dictionaries together.</p>
  
  <p>I am receiving an <code>unsupported operand types</code> error.</p>
  
  <p>Here is my code: </p>
  
  <pre><code>def add_student():
      global Snumber
      global iCode
      global kCode
      Snumber = Student_number.get()
      Sname = Student_name.get()
      Ssurnname = Student_surname.get()
      Sdetail = Student_detail.get()
      i = Students(Snumber,Sname,Ssurnname,Sdetail)
      Sinfo[Snumber]=[Sname,Ssurnname,Sdetail]
  
     iName = Student_subject.get()
     iCode = Student_code.get()
     iMark1 = Student_Mark1.get()
     iMark2 = Student_Mark2.get()
     iMark3 = Student_Mark3.get()
     iProject = Student_project.get()
     j = Subjects(iName,iCode,iMark1,iMark2,iMark3,iProject)
     SSubject[iCode]=[iName,iMark1,iMark2,iMark3,iProject]
  
    kCourse = Degree_course.get()
    kCode = Degree_code.get()
    kYear = Degree_year.get()
    v = Degrees(kCourse,kCode,kYear)
    SDegree[kCode]=[kCourse,kYear]
  
    popup_add()
    student_list = (Sinfo.items() + SSubject.items() + SDegree.items())
    print(student_list)
  </code></pre>
  
  <p>I believe my problem is in:</p>
  
  <pre><code>  student_list = (Sinfo.items() + SSubject.items() + SDegree.items())
    print(student_list)
  </code></pre>