pandas在少数行中联机附加数据

Question

我的脚本在每次迭代中从第2行写入excel文件。但是我需要它每次在最后一行下附加数据。

代码需要从最后一行批量写入新数据

代码在

下面

import scrapy
from scrapy.crawler import CrawlerProcess
import pandas as pd
class plateScraper(scrapy.Spider):
name = 'scrapePlate'
allowed_domains = ['dvlaregistrations.direct.gov.uk']
def start_requests(self):
df=pd.read_excel('data.xlsx')
columnA_values=df['PLATE']
for row in columnA_values:
global  plate_num_xlsx
plate_num_xlsx=row
base_url =f"https://dvlaregistrations.direct.gov.uk/search/results.html?search={plate_num_xlsx}&action=index&pricefrom=0&priceto=&prefixmatches=&currentmatches=&limitprefix=&limitcurrent=&limitauction=&searched=true&openoption=&language=en&prefix2=Search&super=&super_pricefrom=&super_priceto="
url=base_url
yield scrapy.Request(url)
def parse(self, response):
itemList=[]
for row in response.css('div.resultsstrip'):
plate = row.css('a::text').get()
price = row.css('p::text').get()
if plate_num_xlsx==plate.replace(" ","").strip():
item= {"plate": plate.strip(), "price": price.strip()}
itemList.append(item)
yield  item
else:
item = {"plate": plate.strip(), "price": "-"}
itemList.append(item)
yield item
with pd.ExcelWriter('output_res.xlsx', mode='a',if_sheet_exists='overlay') as writer:
df_output = pd.DataFrame(itemList)
df_output.to_excel(writer, sheet_name='result', index=False, header=True)
process = CrawlerProcess()
process.crawl(plateScraper)
process.start()

它批量写入数据，我的意思是每次重写12行，而不是追加和向下。很奇怪，不是吗?想听听原因和如何修复它写上下所有的数据

Answer 1

试试-

with pd.ExcelWriter('output.xlsx',  mode='a') as writer: 
df_output=pd.DataFrame(itemList)
df_output.to_excel(writer, sheet_name='result',index=False,header=True)