python - Django 使用 try : and except:

Question

我想知道是否可以编写一个处理异常的方法，比如处理 2 个或更多异常，但要执行不同的任务。

我正在使用 Django==1.6.1 和 Python 2.7

try:
    foo_instance = foo.objects.get(field_name='unknown')

except foo.DoesNotExist:
    new_rec = foo.objects.create(field_name='unknown')
    new_rec.save()

    foo_instance = foo.objects.get(field_name='unknown')

except foo.MultipleObjectsReturned:
    foo_list = foo.objects.filter(field_name='unknown')
    for record in foo_list[1:]:
       print 'Deleting foo id: ', record.id
       record.delete()

    foo_instance = foo.objects.get(field_name='unknown')

Answer 1

您可以使用多个 try: except: 但在您当前的情况下为什么不使用 get_or_create ？

try: expect: 包含“Exception”上的所有错误。因为这个语法是全部

except Exception as e:

get_or_create(defaults=None, **kwargs)

A convenience method for looking up an object with the given kwargs(may be empty if your model has defaults for all fields), creating oneif necessary.

Returns a tuple of (object, created), where object is the retrieved orcreated object and created is a boolean specifying whether a newobject was created.

这会将您的上述代码减少为 -

 obj, created = foo.objects.get_or_create(field_name='unknown')
 if created:
     obj.save()

我认为 get_or_create 提高了 IntegrityError或 MultipleObjectsReturned , 处理这些只需尝试将其包装起来:

try:
    obj, created = foo.objects.get_or_create(field_name='unknown')
    if created:
        obj.save()
except IntegrityError: 
    #do something
except MultipleObjectsReturned:
    #do something else
except Exception as e:
    raise e