How to rotate proxies and user agents

I am writing a Scrapy program and I login and scrape data for different playing cards on this website,http://www.starcitygames.com/buylist/. But I only scrape ID values from this url and then I redirect to a different URL using that ID number and scrape that JSON webpage and do that for all 207 different categories of cards. I looks a little more authentic then just going straight to URL with the JSON data. Anyways I have written Scrapy program before with multiple URLs and I am able to set those programs up to rotate proxies and user agents, but how would I do it in this program? Since there is technically only one URL, like is there a way to set it up to switch to a different proxy and user agent after it scrapes like 5 or so different JSON data pages? I do not want it to rotate randomly. I would like it to scrape the same JSON webpage with the same proxy and user agent each time. I hope that all makes sense. This might be a little broad for stack overflow but I have no idea how to do this so I figured I would ask anyways to see if anyone has any good ideas on how to do this.

# Import needed functions and call needed python files
import scrapy
import json
from scrapy.spiders import Spider
from scrapy_splash import SplashRequest
from ..items import DataItem

# Spider class
class LoginSpider(scrapy.Spider):
    # Name of spider
    name = "LoginSpider"

    #URL where dated is located
    start_urls = ["http://www.starcitygames.com/buylist/"]

    # Login function
    def parse(self, response):
        # Login using email and password than proceed to after_login function
        return scrapy.FormRequest.from_response(
        response,
        formcss='#existing_users form',
        formdata={'ex_usr_email': 'example@email.com', 'ex_usr_pass': 'password'},
        callback=self.after_login
        )


    # Function to barse buylist website
    def after_login(self, response):
        # Loop through website and get all the ID numbers for each category of card and plug into the end of the below
        # URL then go to parse data function
        for category_id in response.xpath('//select[@id="bl-category-options"]/option/@value').getall():
            yield scrapy.Request(
                    url="http://www.starcitygames.com/buylist/search?search-type=category&id={category_id}".format(category_id=category_id),
                    callback=self.parse_data,
                    )
    # Function to parse JSON dasta
    def parse_data(self, response):
        # Declare variables
        jsonreponse = json.loads(response.body_as_unicode())
        # Call DataItem class from items.py
        items = DataItem()

        # Scrape category name
        items['Category'] = jsonreponse['search']
        # Loop where other data is located
        for result in jsonreponse['results']:
            # Inside this loop, run through loop until all data is scraped
            for index in range(len(result)):
                # Scrape the rest of needed data
                items['Card_Name'] = result[index]['name']
                items['Condition'] = result[index]['condition']
                items['Rarity'] = result[index]['rarity']
                items['Foil'] = result[index]['foil']
                items['Language'] = result[index]['language']
                items['Buy_Price'] = result[index]['price']
                # Return all data
                yield items

Solution

I will recomend this package for you Scrapy-UserAgents

pip install scrapy-useragents

In your setting.py file

DOWNLOADER_MIDDLEWARES = {
'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware': None,
'scrapy_useragents.downloadermiddlewares.useragents.UserAgentsMiddleware': 500,

}

User Agents example List to rotate

More User Agents

USER_AGENTS = [
    ('Mozilla/5.0 (X11; Linux x86_64) '
     'AppleWebKit/537.36 (KHTML, like Gecko) '
     'Chrome/57.0.2987.110 '
     'Safari/537.36'),  # chrome
    ('Mozilla/5.0 (X11; Linux x86_64) '
     'AppleWebKit/537.36 (KHTML, like Gecko) '
     'Chrome/61.0.3163.79 '
     'Safari/537.36'),  # chrome
    ('Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:55.0) '
     'Gecko/20100101 '
     'Firefox/55.0'),  # firefox
    ('Mozilla/5.0 (X11; Linux x86_64) '
     'AppleWebKit/537.36 (KHTML, like Gecko) '
     'Chrome/61.0.3163.91 '
     'Safari/537.36'),  # chrome
    ('Mozilla/5.0 (X11; Linux x86_64) '
     'AppleWebKit/537.36 (KHTML, like Gecko) '
     'Chrome/62.0.3202.89 '
     'Safari/537.36'),  # chrome
    ('Mozilla/5.0 (X11; Linux x86_64) '
     'AppleWebKit/537.36 (KHTML, like Gecko) '
     'Chrome/63.0.3239.108 '
     'Safari/537.36'),  # chrome
]

Be careful this middleware can’t handle the situation that the COOKIES_ENABLED is True, and the website binds the cookies with User-Agent, it may cause unpredictable result of the spider.