Re: Simplifying code with multiple loops and logic, into queryset aggregates

Thank you Matthew. Excellent advise as always. When I started off with this project 5 months ago, I was a beginner to both django and python. I've come a bit along the journey. That customer model is the first model I created, and I was unaware of these conventions. By the time I realized that, the project has branched into several apps, and the code now runs into thousands of lines of code. I didnt change the naming due to fear of breaking other code. :)

Nowadays I do it more "pythonically". Still, it's great to have people like you offer excellent general advise to help budding enthusiasts!

Sincerely yours,

 Joel G Mathew

On Tue, 30 Apr 2019 at 20:33, Matthew Pava <Matthew.Pava@iss.com> wrote:

It was a little difficult to follow your message because the formatting is non-standard, but I think this might be what you're looking for.

Also, you should try to follow more Python coding conventions: models start with an upper case letter. Variables start with a lower case letter.

 

And you probably want to use a QuerySet Manager on Customer. Maybe a query like this:

Customer.objects.annotate(is_admitted=Case(When(admission_set__discharged=False, then=True), default=False).distinct()

 

 

From: django-users@googlegroups.com [mailto:django-users@googlegroups.com] On Behalf Of Joel Mathew
Sent: Tuesday, April 30, 2019 9:22 AM
To: django-users@googlegroups.com
Subject: Simplifying code with multiple loops and logic, into queryset aggregates

 

My models:

 

    class customer(models.Model):

        cstid = models.AutoField(primary_key=True, unique=True)

        insurance_number = models.CharField(max_length=100, blank=True, null=True)

        name = models.CharField(max_length=35)

        ageyrs = models.IntegerField(blank=True)

 

    class Admission(models.Model):

        id = models.AutoField(primary_key=True, unique=True)

        clinic = models.ForeignKey(Clinic, on_delete=models.CASCADE)

        customer = models.ForeignKey(customer, on_delete=models.CASCADE)

        diagnosis = models.CharField(max_length=2000, default='', blank=True)

        date_admission = models.DateTimeField(default=timezone.now)

        ward = models.ForeignKey(Ward, on_delete=models.CASCADE)

        bed = models.ForeignKey(Bed, on_delete=models.CASCADE)

        discharged = models.BooleanField(default=False)

        ip_number = models.IntegerField(blank=True)

        ip_prefix = models.CharField(max_length=20, default='', blank=True)

 

My objective: Set a variable to a query filter, adding a property, 'is_admitted' to the queryset, so that I can pass this query set to the template and use the property while displaying data.

 

Code:

 

    def is_admitted(cust):

        admission = Admission.objects.filter(customer=cust, discharged=False)

        admission_results = len(admission)

        if admission_results > 0:

            return True

        return False

 

    my_q = or_q_if_truthfull(

        cstid=HospitalID,

        name__lower__contains=name.lower() if name else None,

        ageyrs=ageyrs if ageyrs.isdigit() else None,

        agemnths=agemnths if agemnths.isdigit() else None,

        mobile__contains=mobile if mobile else None,

        alternate__contains=alternate if alternate else None,

        email__lower__contains=email.lower() if email else None,

        address__lower__contains=address.lower() if address else None,

        city__lower__contains=city.lower() if city else None

    )

    ORSearchResult = customer.objects.filter(my_q, linkedclinic=clinicobj)

    cust_set = []

    cust_admission_status = []

    for cust in ORSearchResult:

        cust_set.append(cust)

        cust_admission_status.append(is_admitted(cust))

        print(f"Customer name: {cust.name} Admission status: {is_admitted(cust)}")

    cust_templ_set = zip(cust_set, cust_admission_status)

 

And in template, I will do:

 

    {% for cust, status in cust_templ_set %}

        {{ cust.name }} {{ status }}

    {% endfor %}

 

I want to understand how I can convert my above code by generating an aggregate over the queryset, so that I can use a property of the query, and change the template code to the following, and avoid the loop in the view, and the zip. So that the template code becomes:

 

    {% for cust in customers %}

        {{ cust.name }} {{ cust.status }}

    {% endfor %}  

 

I am not sure whether I am making complete sense, and can explain further.

Sincerely yours,

 Joel G Mathew

 

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