Padding printed output of tabular data

问题:

I know this is probably dead simple, but I've got some data such as this in one file:

Artichoke

Green Globe, Imperial Star, Violetto

24" deep

Beans, Lima

Bush Baby, Bush Lima, Fordhook, Fordhook 242

12" wide x 8-10" deep

that I'd like to be able to format into a nice TSV type of table, to look something like this:

    Name  | Varieties    | Container Data
----------|------------- |-------
some data here nicely padded with even spacing and right aligned text 

回答1:

This is a reasonably full example that assumes the following

• Your list of products is contained in a file called veg.txt
• Your data is arranged across three lines per record with the fields on consecutive lines

I am a bit of a noob to rails so there are undoubtedly better and more elegant ways to do this

#!/usr/bin/ruby

class Vegetable

  @@max_name ||= 0  
  @@max_variety ||= 0  
  @@max_container ||= 0  

  attr_reader :name, :variety, :container

  def initialize(name, variety, container)
    @name = name
    @variety = variety
    @container = container  

    @@max_name = set_max(@name.length, @@max_name)  
    @@max_variety = set_max(@variety.length, @@max_variety)  
    @@max_container = set_max(@container.length, @@max_container)
  end

  def set_max(current, max)
    current > max ? current : max
  end

  def self.max_name  
    @@max_name  
  end  

  def self.max_variety  
    @@max_variety  
  end  

  def self.max_container()  
    @@max_container  
  end  

end

    products = []


    File.open("veg.txt") do | file|

      while name = file.gets
        name = name.strip
        variety = file.gets.to_s.strip
        container = file.gets.to_s.strip
        veg = Vegetable.new(name, variety, container)
        products << veg
      end
    end

    format="%#{Vegetable.max_name}s\t%#{Vegetable.max_variety}s\t%#{Vegetable.max_container}s\n"
    printf(format, "Name", "Variety", "Container")
    printf(format, "----", "-------", "---------")
    products.each do |p|
        printf(format, p.name, p.variety, p.container)
    end

The following sample file

Artichoke
Green Globe, Imperial Star, Violetto
24" deep
Beans, Lima
Bush Baby, Bush Lima, Fordhook, Fordhook 242
12" wide x 8-10" deep
Potatoes
King Edward, Desiree, Jersey Royal
36" wide x 8-10" deep

Produced the following output

       Name                                      Variety                Container
       ----                                      -------                ---------
  Artichoke         Green Globe, Imperial Star, Violetto                 24" deep
Beans, Lima Bush Baby, Bush Lima, Fordhook, Fordhook 242    12" wide x 8-10" deep
   Potatoes           King Edward, Desiree, Jersey Royal    36" wide x 8-10" deep

回答2:

Try String#rjust(width):

"hello".rjust(20)           #=> "               hello"

回答3:

I wrote a gem to do exactly this: http://tableprintgem.com

回答4:

No one has mentioned the "coolest" / most compact way -- using the % operator -- for example: "%10s %10s" % [1, 2]. Here is some code:

xs = [
  ["This code", "is", "indeed"],
  ["very", "compact", "and"],
  ["I hope you will", "find", "it helpful!"],
]
m = xs.map { |_| _.length }
xs.each { |_| _.each_with_index { |e, i| s = e.size; m[i] = s if s > m[i] } }
xs.each { |x| puts m.map { |_| "%#{_}s" }.join(" " * 5) % x }

Gives:

      This code          is          indeed
           very     compact             and
I hope you will        find     it helpful!

Here is the code made more readable:

max_lengths = xs.map { |_| _.length }
xs.each do |x|
  x.each_with_index do |e, i|
    s = e.size
    max_lengths[i] = s if s > max_lengths[i]
  end
end
xs.each do |x|
  format = max_lengths.map { |_| "%#{_}s" }.join(" " * 5)
  puts format % x
end

回答5:

another gem: https://github.com/visionmedia/terminal-table Terminal Table is a fast and simple, yet feature rich ASCII table generator written in Ruby.

回答6:

I have a little function to print a 2D array as a table. Each row must have the same number of columns for this to work. It's also easy to tweak to your needs.

def print_table(table)
  # Calculate widths
  widths = []
  table.each{|line|
    c = 0
    line.each{|col|
      widths[c] = (widths[c] && widths[c] > col.length) ? widths[c] : col.length
      c += 1
    }
  }
  # Indent the last column left.
  last = widths.pop()
  format = widths.collect{|n| "%#{n}s"}.join(" ")
  format += " %-#{last}s\n"
  # Print each line.
  table.each{|line|
    printf format, *line
  }
end

回答7:

Kernel.sprintf should get you started.