爬虫将数据更新为数组，在循环中生成

Question

我希望使用循环连续爬行和更新数组值，因为我需要单击某个按钮才能获得数组上的下一个值。然而，在循环内部，它似乎像并行线程一样工作，并且这个项目产生了很多次。我想要的是只进行一次循环，更新数据和生成项目。示例:当前输出：

{'field1': 'data1',
 'filed2' : 'data2',
 'field3' : ['data31']}

{'field1': 'data1',
 'filed2' : 'data2',
 'field3' : ['data32']}

{'field1': 'data1',
 'filed2' : 'data2',
 'field3' : ['data33']}

预期：

{'field1': 'data1',
 'filed2' : 'data2',
 'field3' : ['data31', 'data32', 'data3']}

这是我的密码

def parse_individual_listings(self, response):
     ...
     data = {}
     data[field1] = 'data1'
     data[field1] = 'data2'
     ...
     for i in range(3):
         yield scrapy.Request(
                urlparse.urljoin(response.url, link['href']), #different link
                callback=self.parse_individual_tabs,
                meta={'data': data, 'n':i};
         )
def parse_individual_tabs(self, response):
     data = response.meta['data']
     i = response.meta['i']
     ...
     # keep populating `data`
     data[field3][i] = "data3[i]"  #this value change when I click a button to update
     yield data

Answer 1

尝试使用inline_requests库(https://pypi.org/project/scrapy-inline-requests/)。让我们在同一个函数中提出请求。将数据收集到一个对象而不是产生不同的数据是有用的。用一些伪代码检查这个示例：

from inline_requests import inline_requests
from scrapy import Selector

@inline_requests
def parse_individual_listings(self, response):
    ...
    data = {}
    data[field1] = 'data1'
    data[field1] = 'data2'
     ...
    for i in range(3):
        extra_req = yield scrapy.Request(
            response.urljoin(link['href']), #different link
        )
        # apply your logics here, say extract some data
        sel = Selector(text=extra_req.text)
        data['field3'].append(sel.css('some css selector').get())
    yield data

Answer 2

遵循多线程和不同步的思想，我最终在parse_individual_tabs中使用互斥锁，它看起来工作得很好。

from threading import Lock
...
mutex = Lock()
count = 0
...
def parse_individual_tabs(self, response):
 self.mutex.acquire(1)
 try:
    count += 1
    data = response.meta['data']
    i = response.meta['i']
    ...
    # keep populating `data`
    data[field3][i] = "data3[i]"  #this value change when I click a button to update
 finally:
        self.mutex.release()
 if (count == 3):   #check if this is callback of last yield Request
     yield data
 else:
     return