Question

我正在研究scrapy爬虫，这个问题让我感到困扰，因为我已经被困了好几天了。

当我使用＆＃34;？＆＃34;这个占位符功能正常工作而不是＆＃34;％s＆＃34;对于SQLite数据库。但在使用＆＃34;？＆＃34;当数据库切换到MySQL时，它显示：

＆＃34; TypeError：在字符串格式化期间并非所有参数都被转换＆＃34;

即使我付出了很多努力来修改代码并更改占位符（据说是？），它仍然显示：

＆＃34; query = query％self._escape_args（args，conn）ValueError：不支持的格式字符＆＃39;，＆＃39; ＆＃34;

更具体地说：

Traceback (most recent call last):

  File "/usr/lib64/python3.4/dist-packages/twisted/internet/defer.py", line 653, in _runCallbacks
    current.result = callback(current.result, *args, **kw)

File "/home/ec2-user/lulu_testing/get_download_file/hello_scrapy/hello/hello/pipelines.py", line 42, in process_item
    self.cur.execute(insert_query, insert_values)

File "/usr/lib/python3.4/dist-packages/pymysql/cursors.py", line 163, in execute
    query = self.mogrify(query, args)

File "/usr/lib/python3.4/dist-packages/pymysql/cursors.py", line 142, in mogrify
    query = query % self._escape_args(args, conn)

ValueError: unsupported format character ',' (0x2c) at index 94

mysql版本的pipline

import pymysql
import scrapy
from hello.items import HelloItem

class HelloPipeline(object):

def __init__(self):#

    self.conn = pymysql.connect(host="localhost", port=3306, user="root", passwd="lulu", db="test", charset="utf8", use_unicode=True)
    self.cur = self.conn.cursor()


    self.cur.execute("drop table IF EXISTS test;")
    self.conn.commit()

    self.cur.execute("create table if not EXISTS table_test_4(test0 text, test1 text, test2 text, test3 text,test4 text, test5 text, test6 text, test7 text, test8 text, test9 text);")
    self.conn.commit()

    #pass


def process_item(self, item, spider):#

    col = ",".join(item.keys())
    placeholders = ",".join(len(item) * "%s")

    insert_query = "INSERT INTO test_table_4({0}) VALUES({1});".format(col,placeholders)

    insert_values = tuple(item.values())


    self.cur.execute(insert_query, insert_values)

    return item

def close_spider(self, spider):#
    self.cur.close()
    self.conn.close()
    #pass

SQLite版本（我使用的是b4）

import sqlite3
import scrapy
from hello.items import HelloItem

class HelloPipeline(object):

def open_spider(self, spider):#
    self.conn = sqlite3.connect("test_database_ver_2018_03_31.sqlite")
    self.cur = self.conn.cursor()
    self.cur.execute("create table if not exists test_table(test0 text, test1 text, test2 text, test3 text,test4 text, test5 text, test6 text, test7 text, test8 text, test9 text);")        
    #pass

def close_spider(self, spider):#
    self.conn.commit()
    self.conn.close()
    #pass

def process_item(self, item, spider):#

    col = ",".join(item.keys())       
    placeholders = ",".join(len(item) * "?")
    sql = "insert into test_table({}) values({})"


    self.cur.execute(sql.format(col, placeholders), tuple(item.values()))


    return item

主要scrapy爬虫程序的数据设置

    testitem = HelloItem()

    testitem["test0"] = house_detail.select(".houseInfoTitle")[0].text        
    testitem["test1"] = house_detail.select(".pageView")[0].text 
    testitem["test2"] = house_detail.select(".detailInfo")[0].text
    testitem["test3"] = house_detail.select(".houseIntro")[0].text
    testitem["test4"] = house_detail.select(".lifeBox")[0].text
    testitem["test5"] = house_detail.select(".labelList")[0].text
    testitem["test6"] = house_detail.select(".facility")[0].text
    testitem["test7"] = str(house_detail.select(".userInfo"))
    testitem["test8"] = str(house_detail.select(".banner"))
    testitem["test9"] = str(house_detail.select("#show"))

    return testitem

项目设置

import scrapy


class HelloItem(scrapy.Item):

test0 = scrapy.Field()
test1 = scrapy.Field()
test2 = scrapy.Field()
test3 = scrapy.Field()
test4 = scrapy.Field()
test5 = scrapy.Field()
test6 = scrapy.Field()
test7 = scrapy.Field()
test8 = scrapy.Field()
test9 = scrapy.Field()

Answer 1

问题是这一行：

placeholders = ",".join(len(item) * "%s")

没有做你期望的事。

>>> item = {'a': 1, 'b': 2, 'c': 3}
>>> placeholders = ",".join(len(item) * "%s")
>>> print(placeholders)
%,s,%,s,%,s

",".join(len(item) * "%s")执行两项操作 - 计算len(item) * "%s"，然后将结果与','结合。

len(item) * '%s'的结果是字符串（或 iterable ）'%s%s%s'。 str.join(iterable)返回一个字符串，其中包含 iterable separated by the string that provides the method的所有元素。所以调用的结果是

','.join('%s%s%s') 是

'%,s,%,s,%,s'，而不是'%s,%s,%s'

你想做

>>> ",".join(len(item) * ["%s"])
'%s,%s,%s'

或

>>> ",".join('%s' for _ in item)
'%s,%s,%s'

以便str.join在'%s'字符串的可迭代字符上运行，而不是像'%s%s%s'这样的单个字符串。 `

ValueError：mysql scrapy pipline中不支持的格式字符

1 个答案: