python - 如何避免太多 if - else block 在 python 中

Question

我编写了一个检查输入中的 4 个参数并在输出中显示结果列表的类。此参数中只有一个是必需的，因此我有 7 个 if - else 嵌套 block 。我想指定所述条件是否正常工作。

我在徘徊是否有更聪明的方式来写这个:

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

在内部，您传递给函数的关键字参数只是一个dict。所以自己构建它并使用 **name 语法将它传递给函数:

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})