how to avoid too many if - else blocks in python

Question

I wrote a class that check 4 parameters in input and shows a list a result in output. Only one of this parameter is required, therefore i have 7 if - else nested blocks. I want to specify that the condition as stated works properly.

I was wandering if there was a smarter way to write this:

if cd['subject'] is None:
    if cd['school'] == '':
        if cd['price']:
            files = File.objects.filter(name__contains=cd['name'], price = '0.0')
        else:
            files = File.objects.filter(name__contains=cd['name'])
    else:
        if cd['price']:
            files = File.objects.filter(name__contains=cd['name'], school = cd['school'], price = '0.0')
        else:
            files = File.objects.filter(name__contains=cd['name'], school = cd['school'])
else:
    if cd['school'] == '':
        if cd['price']:
            files = File.objects.filter(name__contains=cd['name'], subject = cd['subject'], price = '0.0')
        else:
            files = File.objects.filter(name__contains=cd['name'], subject = cd['subject'])
    else:
        if cd['price']:
            files = File.objects.filter(name__contains=cd['name'], school = cd['school'], subject = cd['subject'], price = '0.0')
        else:
            files = File.objects.filter(name__contains=cd['name'], school = cd['school'], subject = cd['subject'])
return render(request, 'search.html', {'files': files, 'request': request})

Please fix your code indentation; why are you mixing None, empty string '' and boolean coersion (if <variable>) in comparaisons? — alko
– alko, Commented Dec 23, 2013 at 21:03
Because the variables come from a Django form and are different form fields. I forgot to say, the condition works just fine, I was wondering if there was a smarter (or more elegant if you may) way to say the same thing. — Higure
– Higure, Commented Dec 23, 2013 at 21:06
This might be better suited on codereview.stackexchange.com. — user2555451
– user2555451, Commented Dec 23, 2013 at 21:10

Nils Werner · Accepted Answer · 2013-12-24 07:18:50Z

6

Internally, the keyword arguments you're passing to the function are just a dict. So build it yourself and pass it to the function using the **name syntax:

args = {}

args['name__contains'] = cd['name']

if cd['subject'] is not None:
    args['subject'] = cd['subject']
if cd['school'] != '':
    args['school'] = cd['school']
if cd['price']:
    args['price'] = cd['price']

files = File.objects.filter(**args)
return render(request, 'search.html', {'files': files, 'request': request})

edited Dec 24, 2013 at 7:18

answered Dec 23, 2013 at 21:10

Nils Werner

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1 Comment

Higure Over a year ago

Tuned a little the condition and worked like a charm.

bruno desthuilliers · Accepted Answer · 2013-12-23 21:07:23Z

0

Build a dict with the keyword args for your call to filter(), then pass it using the **kwargs syntax.

answered Dec 23, 2013 at 21:07

bruno desthuilliers

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