pipeline | 易学教程

How to access scrapy settings from item Pipeline

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问题 How do I access the scrapy settings in settings.py from the item pipeline. The documentation mentions it can be accessed through the crawler in extensions, but I don't see how to access the crawler in the pipelines. 回答1: The way to access your Scrapy settings (as defined in settings.py ) from within your_spider.py is simple. All other answers are way too complicated. The reason for this is the very poor maintenance of the Scrapy documentation, combined with many recent updates & changes.

How do I make a Jenkins job start after multiple simultaneous upstream jobs succeed?

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In order to get the fastest feedback possible, we occasionally want Jenkins jobs to run in Parallel. Jenkins has the ability to start multiple downstream jobs (or 'fork' the pipeline) when a job finishes. However, Jenkins doesn't seem to have any way of making a downstream job only start of all branches of that fork succeed (or 'joining' the fork back together). Jenkins has a "Build after other projects are built" button, but I interpret that as "start this job when any upstream job finishes" (not "start this job when all upstream jobs succeed"). Here is a visualization of what I'm talking

Assign intermediate output to temp variable as part of dplyr pipeline

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问题 Q: In an R dplyr pipeline, how can I assign some intermediate output to a temp variable for use further down the pipeline? My approach below works. But it assigns into the global frame, which is undesirable. There has to be a better way, right? I figured my approach involving the commented line would get the desired results. No dice. Confused why that didn't work. df <- data.frame(a = LETTERS[1:3], b=1:3) df %>% filter(b < 3) %>% assign("tmp", ., envir = .GlobalEnv) %>% # works #assign("tmp",

why it is so slow with 100,000 records when using pipeline in redis?

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问题 It is said that pipeline is a better way when many set/get is required in redis, so this is my test code: public class TestPipeline { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub JedisShardInfo si = new JedisShardInfo("127.0.0.1", 6379); List<JedisShardInfo> list = new ArrayList<JedisShardInfo>(); list.add(si); ShardedJedis jedis = new ShardedJedis(list); long startTime = System.currentTimeMillis(); ShardedJedisPipeline pipeline = jedis

Benefits of using short-circuit evaluation

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问题 boolean a = false, b = true; if ( a && b ) { ... }; In most languages, b will not get evaluated because a is false so a && b cannot be true. My question is, wouldn't short circuiting be slower in terms of architecture? In a pipeline, do you just stall while waiting to get the result of a to determine if b should be evaluated or not? Would it be better to do nested ifs instead? Does that even help? Also, does anyone know what short-circuit evaluation is typically called? This question arose

In what conditions does powershell unroll items in the pipeline?

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问题 Consider the following: function OutputArray{ $l = @(,(10,20)) $l } (OutputArray) -is [collections.ienumerable] # C:\ PS> True (OutputArray).Count # C:\ PS> 2 $l is "unrolled" when it enters the pipeline. This answer states that powershell unrolls all collections. A hashtable is a collection. However, a hashtable is of course unaffected by the pipeline: function OutputHashtable{ $h = @{nested=@{prop1=10;prop2=20}} $h } (OutputHashtable) -is [collections.ienumerable] # C:\ PS> True

How do you determine if WPF is using Hardware or Software Rendering?

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I'm benchmarking a WPF application on various platforms and I need an easy way to determine if WPF is using hardware or software rendering. I seem to recall a call to determine this, but can't lay my hands on it right now. Also, is there an easy, code based way to force one rendering pipeline over the other? rudigrobler Check the RenderCapability.Tier http://msdn.microsoft.com/library/ms742196(v=vs.100).aspx http://msdn.microsoft.com/en-us/library/system.windows.media.rendercapability_members.aspx [ UPDATE ] RenderCapability.IsPixelShaderVersionSupported - Gets a value that indicates whether

Efficient XSLT pipeline in Java (or redirecting Results to Sources)

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问题 I have a series of XSL 2.0 stylesheets that feed into each other, i.e. the output of stylesheet A feeds B feeds C. What is the most efficient way of doing this? The question rephrased is: how can one efficiently route the output of one transformation into another. Here's my first attempt: @Override public void transform(Source data, Result out) throws TransformerException{ for(Transformer autobot : autobots){ if(autobots.indexOf(autobot) != (autobots.size()-1)){ log.debug("Transforming prelim

Scrapy pipeline to export csv file in the right format

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问题 I made the improvement according to the suggestion from alexce below. What I need is like the picture below. However each row/line should be one review: with date, rating, review text and link. I need to let item processor process each review of every page. Currently TakeFirst() only takes the first review of the page. So 10 pages, I only have 10 lines/rows as in the picture below. Spider code is below: import scrapy from amazon.items import AmazonItem class AmazonSpider(scrapy.Spider): name

Writing items to a MySQL database in Scrapy

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问题 I am new to Scrapy, I had the spider code class Example_spider(BaseSpider): name = "example" allowed_domains = ["www.example.com"] def start_requests(self): yield self.make_requests_from_url("http://www.example.com/bookstore/new") def parse(self, response): hxs = HtmlXPathSelector(response) urls = hxs.select('//div[@class="bookListingBookTitle"]/a/@href').extract() for i in urls: yield Request(urljoin("http://www.example.com/", i[1:]), callback=self.parse_url) def parse_url(self, response):