从 CSV 导入 Ruby 数组，第一个字段作为哈希键，然后查找给定标题行的字段值
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原文地址: http://stackoverflow.com/questions/8476769/
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import from CSV into Ruby array, with 1st field as hash key, then lookup a field's value given header row
提问by Marcos
Maybe somebody can help me.
也许有人可以帮助我。
Starting with a CSV file like so:
从像这样的 CSV 文件开始：
Ticker,"Price","Market Cap"
ZUMZ,30.00,933.90
XTEX,16.02,811.57
AAC,9.83,80.02
I manage to read them into an array:
我设法将它们读入数组：
require 'csv'
tickers = CSV.read("stocks.csv", {:headers => true, :return_headers => true, :header_converters => :symbol, :converters => :all} )
To verify data, this works:
为了验证数据，这有效：
puts tickers[1][:ticker]
ZUMZ
However this doesn't:
然而，这不会：
puts tickers[:ticker => "XTEX"][:price]
How would I go about turning this array into a hash using the ticker field as unique key, such that I could easily look up any other field associatively as defined in line 1 of the input? Dealing with many more columns and rows.
我将如何使用股票代码字段作为唯一键将此数组转换为散列，以便我可以轻松地关联地查找任何其他字段，如输入的第 1 行中定义的那样？处理更多的列和行。
Much appreciated!
非常感激！
采纳答案by Marcos
To get the best of both worlds (very fast reading from a huge file AND the benefits of a native Ruby CSV object) my code had since evolved into this method:
为了两全其美（从巨大的文件中快速读取以及原生 Ruby CSV 对象的好处），我的代码已经演变为这种方法：
$stock="XTEX"
csv_data = CSV.parse IO.read(%`|sed -n "1p; /^#{$stock},/p" stocks.csv`), {:headers => true, :return_headers => false, :header_converters => :symbol, :converters => :all}
# Now the 1-row CSV object is ready for use, eg:
$company = csv_data[:company][0]
$volatility_month = csv_data[:volatility_month][0].to_f
$sector = csv_data[:sector][0]
$industry = csv_data[:industry][0]
$rsi14d = csv_data[:relative_strength_index_14][0].to_f
which is closer to my original method, but only reads in one record plus line 1 of the input csv file containing the headers. The inline sedinstructions take care of that--and the whole thing is noticably instant. This this is better than lastbecause now I can access all the fields from Ruby, and associatively, not caring about column numbers anymore as was the case with awk.
这更接近我的原始方法，但只读取一条记录加上包含标题的输入 csv 文件的第 1 行。内联sed指令解决了这个问题——整个过程非常即时。这比上一个更好，因为现在我可以从 Ruby 访问所有字段，并且关联地，不再像awk.
回答by Michael Kohl
Like this (it works with other CSVs too, not just the one you specified):
像这样（它也适用于其他 CSV，而不仅仅是您指定的那个）：
require 'csv'
tickers = {}
CSV.foreach("stocks.csv", :headers => true, :header_converters => :symbol, :converters => :all) do |row|
tickers[row.fields[0]] = Hash[row.headers[1..-1].zip(row.fields[1..-1])]
end
Result:
结果：
{"ZUMZ"=>{:price=>30.0, :market_cap=>933.9}, "XTEX"=>{:price=>16.02, :market_cap=>811.57}, "AAC"=>{:price=>9.83, :market_cap=>80.02}}
You can access elements in this data structure like this:
您可以像这样访问此数据结构中的元素：
puts tickers["XTEX"][:price] #=> 16.02
Edit (according to comment): For selecting elements, you can do something like
编辑（根据评论）：要选择元素，您可以执行以下操作
tickers.select { |ticker, vals| vals[:price] > 10.0 }
回答by Mr. Demetrius Michael
CSV.read(file_path, headers:true, header_converters: :symbol, converters: :all).collect do |row|
Hash[row.collect { |c,r| [c,r] }]
end
回答by clouddra
To add on to Michael Kohl's answer, if you want to access the elements in the following manner
补充迈克尔科尔的回答，如果你想通过以下方式访问元素
puts tickers[:price]["XTEX"] #=> 16.02
You can try the following code snippet:
您可以尝试以下代码片段：
CSV.foreach("Workbook1.csv", :headers => true, :header_converters => :symbol, :converters => :all) do |row|
hash_row = row.headers[1..-1].zip( (Array.new(row.fields.length-1, row.fields[0]).zip(row.fields[1..-1])) ).to_h
hash_row.each{|key, value| tickers[key] ? tickers[key].merge!([value].to_h) : tickers[key] = [value].to_h}
end
回答by Jesse Smith
Not as 1-liner-ie but this was more clear to me.
不是 1-liner-ie，但这对我来说更清楚。
csv_headers = CSV.parse(STDIN.gets)
csv = CSV.new(STDIN)
kick_list = []
csv.each_with_index do |row, i|
row_hash = {}
row.each_with_index do |field, j|
row_hash[csv_headers[0][j]] = field
end
kick_list << row_hash
end
回答by Marcos
While this isn't a 100% native Ruby solution to the original question, should others stumble here and wonder what awk call I wound up using for now, here it is:
虽然这不是原始问题的 100% 原生 Ruby 解决方案，但如果其他人在这里绊倒并想知道我现在最终使用的是什么 awk 调用，这里是：
$dividend_yield = IO.readlines("|awk -F, '==\"#{$stock}\" {print }' datafile.csv")[0].to_f
where $stock is the variable I had previously assigned to a company's ticker symbol (the wannabe key field). Conveniently survives problems by returning 0.0 if: ticker or file or field #9 not found/empty, or if value cannot be typecasted to a float. So any trailing '%' in my case gets nicely truncated.
其中 $stock 是我之前分配给公司股票代码（想要的关键字段）的变量。在以下情况下通过返回 0.0 方便地解决问题：股票代码或文件或字段 #9 未找到/为空，或者值不能被类型转换为浮点数。因此，在我的情况下，任何尾随 '%' 都会被很好地截断。
Note that at this point one could easily add more filters within awk to have IO.readlines return a 1-dim array of output lines from the smaller resulting CSV, eg.
请注意，此时可以轻松地在 awk 中添加更多过滤器，以使 IO.readlines 从较小的结果 CSV 返回一个 1-dim 输出行数组，例如。
awk -F, ' >= 2.01 && > 99.99 {print ##代码##}' datafile.csv
outputs in bash which lines have a DivYld (col 9) over 2.01 and price (col 2) over 99.99. (Unfortunately I'm not using the header row to to determine field numbers, which is where I was ultimately hoping for some searchable associative Ruby array.)
在 bash 中输出哪些行的 DivYld (col 9) 超过 2.01，而 price (col 2) 超过 99.99。（不幸的是，我没有使用标题行来确定字段编号，这是我最终希望获得一些可搜索的关联 Ruby 数组的地方。）
