如何在python中避免使用过多的if - else块

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})

Answer 1

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})

Answer 2

使用关键字args构建一个dict，用于调用filter() ，然后使用**kwargs语法传递它。