Demand:
After the tiem object is created, modify the written table of the original item_ Name value
My item:
class People(scrapy.Item):
table_name = 'people'
id = scrapy.Field()
url_token = scrapy.Field()
name = scrapy.Field()
Solution:
people = People()
people.__class__.table_name='people_20216'
Source code analysis:
If this is what the item says
table_name= scrapy.Field()
After creation, you can directly assign values in this way, which is normal operation
people = People()
people['table_name'] = 'people_20216'
Situation 1:
But if you write like me:
class People(scrapy.Item):
table_name = 'people'
In addition, it can be modified as follows:
people[‘table_ name’] = ‘people_ 20216’
You will report an error:
Traceback (most recent call last):
File "C:\Program Files\Python39\lib\site-packages\twisted\internet\defer.py", line 662, in _runCallbacks
current.result = callback(current.result, *args, **kw)
File "C:\Program Files\Python39\lib\site-packages\scrapy\utils\defer.py", line 150, in f
return deferred_from_coro(coro_f(*coro_args, **coro_kwargs))
File "E:\codedata\gitee\pySpace\study\npoms\npoms\pipelines.py", line 62, in process_item
item['table_name'] = item.table_name + "_" + mysql_split_util.current_year_month
File "C:\Program Files\Python39\lib\site-packages\scrapy\item.py", line 100, in __setitem__
raise KeyError(f"{self.__class__.__name__} does not support field: {key}")
Corresponding to this section of the original code, the source code covers this:
Case 2:
If you write like this
people.table_ name’= ‘people_ 20216’
You will report an error:
Traceback (most recent call last):
File "C:\Program Files\Python39\lib\site-packages\twisted\internet\defer.py", line 662, in _runCallbacks
current.result = callback(current.result, *args, **kw)
File "C:\Program Files\Python39\lib\site-packages\scrapy\utils\defer.py", line 150, in f
return deferred_from_coro(coro_f(*coro_args, **coro_kwargs))
File "E:\codedata\gitee\pySpace\study\npoms\npoms\pipelines.py", line 63, in process_item
item.set_table_name(table_name)
File "E:\codedata\gitee\pySpace\study\npoms\npoms\items.py", line 66, in set_table_name
self.table_name = table_name
File "C:\Program Files\Python39\lib\site-packages\scrapy\item.py", line 112, in __setattr__
raise AttributeError(f"Use item[{name!r}] = {value!r} to set field value")
AttributeError: Use item['table_name'] = 'people_202106' to set field value
Corresponding to this section of the original code, the source code also has corresponding interception:
At this time, we need to look at the creation phase of the source code object
The object creation phase is divided into fields and classes, which we can use above__ setitem__ Method to modify the object in fields. So we need to get the class object and modify the values of the properties in the class.
