Scrapy works in shell but spider returns empty csv - shell

Question

I am learning Scrapy. Now I just try to scrapy items and when I call spider:
planefinder]# scrapy crawl planefinder -o /User/spider/planefinder/pf.csv -t csv
it shows tech information and no scraped content (Crawled 0 pages .... etc), and it returns an empty csv file.
The problem is when i test xpath in scrapy shell it works:
>>> from scrapy.selector import Selector
>>> sel = Selector(response)
>>> flights = sel.xpath("//div[#class='col-md-12'][1]/div/div/table//tr")
>>> items = []
>>> for flt in flights:
... item = flt.xpath("td[1]/a/#href").extract_first()
... items.append(item)
...
>>> items
The following is my planeFinder.py code:
# -*-:coding:utf-8 -*-
from scrapy.spiders import CrawlSpider
from scrapy.selector import Selector, HtmlXPathSelector
from planefinder.items import arr_flt_Item, dep_flt_Item
class planefinder(CrawlSpider):
name = 'planefinder'
host = 'https://planefinder.net'
start_url = ['https://planefinder.net/data/airport/PEK/']
def parse(self, response):
arr_flights = response.xpath("//div[#class='col-md-12'][1]/div/div/table//tr")
dep_flights = response.xpath("//div[#class='col-md-12'][2]/div/div/table//tr")
for flight in arr_flights:
arr_item = arr_flt_Item()
arr_flt_url = flight.xpath('td[1]/a/#href').extract_first()
arr_item['arr_flt_No'] = flight.xpath('td[1]/a/text()').extract_first()
arr_item['STA'] = flight.xpath('td[2]/text()').extract_first()
arr_item['From'] = flight.xpath('td[3]/a/text()').extract_first()
arr_item['ETA'] = flight.xpath('td[4]/text()').extract_first()
yield arr_item

Answer 1

Please before going to CrawlSpider please check the docs for Spiders, some of the issues I've found were:
Instead of host use allowed_domains
Instead of start_url use start_urls
It seem that the page needs to have some cookies set or maybe it's using some kind of basic anti-bot protection, and you need to land somewhere else first.
Try this (I've also changed a bit :
# -*-:coding:utf-8 -*-
from scrapy import Field, Item, Request
from scrapy.spiders import CrawlSpider, Spider
class ArrivalFlightItem(Item):
arr_flt_no = Field()
arr_sta = Field()
arr_from = Field()
arr_eta = Field()
class PlaneFinder(Spider):
name = 'planefinder'
allowed_domains = ['planefinder.net']
start_urls = ['https://planefinder.net/data/airports']
def parse(self, response):
yield Request('https://planefinder.net/data/airport/PEK', callback=self.parse_flight)
def parse_flight(self, response):
flights_xpath = ('//*[contains(#class, "departure-board") and '
'./preceding-sibling::h2[contains(., "Arrivals")]]'
'//tr[not(./th) and not(./td[#class="spacer"])]')
for flight in response.xpath(flights_xpath):
arrival = ArrivalFlightItem()
arr_flt_url = flight.xpath('td[1]/a/#href').extract_first()
arrival['arr_flt_no'] = flight.xpath('td[1]/a/text()').extract_first()
arrival['arr_sta'] = flight.xpath('td[2]/text()').extract_first()
arrival['arr_from'] = flight.xpath('td[3]/a/text()').extract_first()
arrival['arr_eta'] = flight.xpath('td[4]/text()').extract_first()
yield arrival

Answer 2

The problem here is not understanding correctly which "Spider" to use, as Scrapy offers different custom ones.
The main one, and the one you should be using is the simple Spider and not CrawlSpider, because CrawlSpider is used for a more deep and intensive search into forums, blogs, etc.
Just change the type of spider to:
from scrapy import Spider
class plane finder(Spider):
...

Answer 3

Check the value of ROBOTSTXT_OBEY in your settings.py file. By default it's set to True (but not when you run shell). Set it to False if you wan't to disobey robots.txt file.