R查询维基媒体服务器

huangapple
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英文:

R Query of a Wikimedia server

问题

我正在尝试查询Cameo数据库。

如果我使用以下URL https://cameo.mfa.org/api.php?action=query&pageids=17051&prop=extracts&format=json，那么我在线上得到一个有效的输出。

然而，如果我使用：

  1. library(httr)
  2. library(jsonlite)
  4. base_url <- "https://cameo.mfa.org/api.php"
  6. query_param <- list(action  = "query",
  7.                     pageids = "17051",
  8.                     format = "json",
  9.                     prop = "extracts"
  10. )
  12. parsed_content <- httr::GET(base_url, query_param)
  14. jsonlite::fromJSON(content(parsed_content, as = "text", encoding = "UTF-8"))

那么 jsonlite 会失败，因为输出是HTML格式而不是JSON。

你对此有什么建议吗？

英文:

I am trying to query the Cameo database.

If I use the URL https://cameo.mfa.org/api.php?action=query&pageids=17051&prop=extracts&format=json, then I get, online, a valid output.

However, if I use:

  1. library(httr)
  2. library(jsonlite)
  4. base_url &lt;- &quot;https://cameo.mfa.org/api.php&quot;
  6. query_param &lt;- list(action  = &quot;query&quot;,
  7.                     pageids = &quot;17051&quot;,
  8.                     format = &quot;json&quot;,
  9.                     prop = &quot;extracts&quot;
  10. )
  12. parsed_content &lt;- httr::GET(base_url, query_param)
  14. jsonlite::fromJSON(content(parsed_content, as = &quot;text&quot;, encoding = &quot;UTF-8&quot;))

Then jsonlite fails because the output is in html format and not json.

Do you have any advice on this?

答案1

得分: 2

httr::GET的第二个参数是config=，这不是你应该分配query_param的位置。而应该将其命名为query=query_param。

  1. res &lt;- httr::GET(base_url, query = query_param)
  2. res
  3. # 响应 [https://cameo.mfa.org/api.php?action=query&amp;pageids=17051&amp;format=json&amp;prop=extracts]
  4. #   日期：2023年07月03日 15:06
  5. #   状态：200
  6. #   内容类型：application/json; charset=utf-8
  7. #   大小：5.22千字节
  8. str(httr::content(res))
  9. # 3个元素的列表
  10. #  $ batchcomplete: 字符串 ""
  11. #  $ warnings     : 1个列表
  12. #   ..$ extracts: 1个列表
  13. #   .. ..$ *: 字符串 "HTML可能存在格式错误和/或不平衡，可能省略内联图像。使用需谨慎。已知问题包括li"| 被截断
  14. #  $ query        : 1个列表
  15. #   ..$ pages: 1个列表
  16. #   .. ..$ 17051: 4个元素的列表
  17. #   .. .. ..$ pageid : 整数 17051
  18. #   .. .. ..$ ns     : 整数 0
  19. #   .. .. ..$ title  : 字符串 "Copper"
  20. #   .. .. ..$ extract: 字符串 "<h2><span id=\"Description\">Description</span></h2>\n<p>A reddish-brown, ductile, metallic element. Copper is "| 被截断
英文:

The second argument to httr::GET is config=, which is not where you should be assigning query_param. Instead name it as query=query_param.

  1. res &lt;- httr::GET(base_url, query = query_param)
  2. res
  3. # Response [https://cameo.mfa.org/api.php?action=query&amp;pageids=17051&amp;format=json&amp;prop=extracts]
  4. #   Date: 2023-07-03 15:06
  5. #   Status: 200
  6. #   Content-Type: application/json; charset=utf-8
  7. #   Size: 5.22 kB
  8. str(httr::content(res))
  9. # List of 3
  10. #  $ batchcomplete: chr &quot;&quot;
  11. #  $ warnings     :List of 1
  12. #   ..$ extracts:List of 1
  13. #   .. ..$ *: chr &quot;HTML may be malformed and/or unbalanced and may omit inline images. Use at your own risk. Known problems are li&quot;| __truncated__
  14. #  $ query        :List of 1
  15. #   ..$ pages:List of 1
  16. #   .. ..$ 17051:List of 4
  17. #   .. .. ..$ pageid : int 17051
  18. #   .. .. ..$ ns     : int 0
  19. #   .. .. ..$ title  : chr &quot;Copper&quot;
  20. #   .. .. ..$ extract: chr &quot;&lt;h2&gt;&lt;span id=\&quot;Description\&quot;&gt;Description&lt;/span&gt;&lt;/h2&gt;\n&lt;p&gt;A reddish-brown, ductile, metallic element. Copper is &quot;| __truncated__

答案2

得分: 1

以下是翻译好的代码部分：

  1. library(httr)
  2. library(jsonlite)
  4. url <- httr::parse_url("https://cameo.mfa.org/api.php")
  5. url$query <- list(
  6.   action = "query",
  7.   pageids = "17051",
  8.   format = "json",
  9.   prop = "extracts"
  10. )
  12. json <- jsonlite::fromJSON(httr::build_url(url))
  15. json$query$pages
  16. #> $`17051`
  17. #> $`17051`$pageid
  18. #> [1] 17051
  19. #> 
  20. #> $`17051`$ns
  21. #> [1] 0
  22. #> 
  23. #> $`17051`$title
  24. #> [1] "Copper"
  25. #> 
  26. #> $`17051`$extract
  27. #> [1] "<h2><span id=\"Description\">Description</span></h2>\n<p>A reddish-brown, ductile, metallic element. Copper is present [...]"

Created on 2023-07-03 with reprex v2.0.2

  2. <details>
  3. <summary>英文:</summary>
  5. A bit different approach:
  7. ``` r
  8. library(httr)
  9. library(jsonlite)
  11. url &lt;- httr::parse_url(&quot;https://cameo.mfa.org/api.php&quot;)
  12. url$query &lt;- list(
  13.   action = &quot;query&quot;,
  14.   pageids = &quot;17051&quot;,
  15.   format = &quot;json&quot;,
  16.   prop = &quot;extracts&quot;
  17. )
  19. json &lt;- jsonlite::fromJSON(httr::build_url(url))
  22. json$query$pages
  23. #&gt; $`17051`
  24. #&gt; $`17051`$pageid
  25. #&gt; [1] 17051
  26. #&gt; 
  27. #&gt; $`17051`$ns
  28. #&gt; [1] 0
  29. #&gt; 
  30. #&gt; $`17051`$title
  31. #&gt; [1] &quot;Copper&quot;
  32. #&gt; 
  33. #&gt; $`17051`$extract
  34. #&gt; [1] &quot;&lt;h2&gt;&lt;span id=\&quot;Description\&quot;&gt;Description&lt;/span&gt;&lt;/h2&gt;\n&lt;p&gt;A reddish-brown, ductile, metallic element. Copper is present [...]&quot;

<sup>Created on 2023-07-03 with reprex v2.0.2</sup>

huangapple
  • 本文由 发表于 2023年7月3日 22:13:27
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