Google App Engine: Database object is not iterable

Question

I'm working on an ecommerce site, using Google App Engine with Python. Here's the entity 'Products' in my datastore:

Now, I'm trying to filter out certain products based on the user preference. The user has the option of selecting these preferences with the help of drop-down options. Here's the code for the same in 'newbooks.html':

<form method = "post">
        <p>Department: </p>
        <select name = "branch">
            <option></option>
            <option>Computers</option>
            <option>EXTC</option>
            <option>IT</option>
            <option>ETRX</option>
            <option>MECH</option>
        </select>
        <br>
        <br>
        <p>Semester: </p>

        <select name = "semester">
            <option></option>
            <option>1</option>
            <option>2</option>
            <option>3</option>
            <option>4</option>
            <option>5</option>
            <option>6</option>
            <option>7</option>
            <option>8</option>
        </select>

        <br>
        <br>
        <p>Publications: </p>
        <select name = "publications">
            <option></option>
            <option>Techmax</option>
            <option>Nandu</option>
            <option>Pearson</option>
            <option>Tata McGraw Hill</option>
            <option>Technical</option>
        </select>
            <br>
        <br>
        <p>Subject: </p>
        <select name = "subject">
            <option></option>
            <option>System Programming and Compiler Construction</option>
            <option>Advanced Microprocessors</option>
            <option>Microprocessors and Interfacing</option>
            <option>Computer Networks</option>
            <option>Data Warehouse and Data Mining</option>
        </select>    

        <br><br>

        <input type = "submit">   
        </form>   

Here's my python code:

class NewBooks(Handler):
    def get(self):
        self.render("newbooks.html")
    def post(self):
        branch = self.request.get("branch")
        semester = self.request.get("semester")
        publications = self.request.get("publications")
        subject = self.request.get("subject")
        if semester:
            yo = int(semester)
        if(branch and semester and publications and subject):
            disp = Products.all().filter("branch =", branch).filter("publisher =", publications).filter("name =", subject).filter("semester =", yo).get()
            self.render("newbooks.html", disp = disp)
        elif(branch and semester and publications):
            disp = Products.all().filter("branch =", branch).filter("publisher =", publications).filter("semester =", yo).get()
            self.render("newbooks.html", disp = disp) 
        elif(branch and semester and subject):
            disp = Products.all().filter("branch =", branch).filter("name =", subject).filter("semester =", yo).get()
            self.render("newbooks.html", disp = disp)  
        elif(branch and publications and subject):
            disp = Products.all().filter("branch =", branch).filter("publisher =", publications).filter("name =", subject).get()
            self.render("newbooks.html", disp = disp)
        elif(semester and publications and subject):
            disp = Products.all().filter("publisher =", publications).filter("name =", subject).filter("semester =", yo).get()
            self.render("newbooks.html", disp = disp)
        elif(branch and semester):
            disp = Products.all().filter("branch =", branch).filter("semester =", yo).get()
            self.render("newbooks.html", disp = disp)
        elif(semester and publications):
            disp = Products.all().filter("publisher =", publications).filter("semester =", yo).get()
            self.render("newbooks.html", disp = disp)  
        elif(publications and subject):
            disp = Products.all().filter("publisher =", publications).filter("name =", subject).get()
            self.render("newbooks.html", disp = disp)
        elif(branch and subject):
            disp = Products.all().filter("branch =", branch).filter("name =", subject).get()
            self.render("newbooks.html", disp = disp) 
        elif(branch and publications):
            disp = Products.all().filter("branch =", branch).filter("publisher =", publications).get()
            self.render("newbooks.html", disp = disp)
        elif(semester and subject):
            disp = Products.all().filter("name =", subject).filter("semester =", yo).get()
            self.render("newbooks.html", disp = disp) 
        elif(branch):
            disp = Products.all().filter("branch =", branch).get()
            self.render("newbooks.html", disp = disp) 
        elif(semester):
            disp = Products.all().filter("semester =", yo).get()
            self.render("newbooks.html", disp = disp)
        elif(publications):
            disp = Products.all().filter("publisher =", publications).get()
            self.render("newbooks.html", disp = disp)  
        elif(subject):
            disp = Products.all().filter("name =", subject).get()
            self.render("newbooks.html", disp = disp)  

However, after the user selects and submits his/her's preferred filtering conditions, I get the following error:

TypeError: 'Products' object is not iterable

What seems to be the problem with my code? Why are the entries in my database not iterable?

Answer 1

Use fetch() to return a list of entities. get() just returns the first entity that matches your query, therefore, it is not iterable.

Answer 2

You're calling get(), which only "returns the first result". You should instead call fetch(), which returns a list of results.