我的items.py档案：
from scrapy.item import Item, Field
from collections import OrderedDict
from types import FunctionType
class StaticOrderHelper(type):
# Requires python3
def __prepare__(name, bases, **kwargs):
return OrderedDict()
def __new__(mcls, name, bases, namespace, **kwargs):
namespace['_field_order'] = [
k
for k, v in namespace.items()
if not k.startswith('__') and not k.endswith('__')
and not isinstance(v, (FunctionType, classmethod, staticmethod))
]
return type.__new__(mcls, name, bases, namespace, **kwargs)
class NewAdsItem(Metaclass=StaticOrderHelper):
AdId = Field()
DateR = Field()
AdURL = Field()
然后使用以下命令将该_field_order项目导入你piplines.py的：
...
from adbot.items import NewAdsItem
...
class DbPipeline(object):
ikeys = NewAdsItem._field_order
...
def createDbTable(self):
print("Creating new table: %s" % self.dbtable )
print("Keys in creatDbTable: \t%s" % ",".join(self.ikeys) )
...
现在，我可以按照正确的外观顺序创建新的数据库表，而不必担心Python以一种意想不到的方式对字典进行奇怪的排序。
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