slhck slhck - 2 years ago 82
Ruby Question

All possible combinations from a hash of arrays in Ruby

What I have:

Let's say I have a hash like this, with various values belonging to one parameter.

a = {}
a[:bitrate] = ["100", "500", "1000"]
a[:fps] = ["15", "30"]
a[:qp] = ["20", "30"]

What I need:

I need some way to iteratively get all the possible combinations of these values, so, with all the parameter/value pairs:

  • bitrate = 100
    fps = 15
    qp = 20

  • bitrate = 500
    fps = 15
    qp = 30

  • ...

The number of parameters (i.e. the keys) and the number of values (i.e. the length of the value arrays) are not known beforehand. Ideally, I'd do something like: do |ret|
puts ret.keys # => ["bitrate", "fps", "qp"]
puts ret.values # => ["100", "15", "20"]

… where the block is called for each possible combination. How can I define

What I (probably) don't need:

Now, I know this: Combine array of array into all possible combinations, forward only, in Ruby, suggesting something like:


But this operates on values and arrays in arrays only, and I need the original reference to the parameter's name.

Answer Source
a = {}
a[:bitrate] = ["100", "500", "1000"]
a[:fps] = ["15", "30"]
a[:qp] = ["20", "30"]

def product_hash(hsh)
  attrs   = hsh.values
  keys    = hsh.keys
  product = attrs[0].product(*attrs[1..-1]){ |p| Hash[ p] }


you'll get

[{:bitrate=>"100", :fps=>"15", :qp=>"20"},
 {:bitrate=>"100", :fps=>"15", :qp=>"30"},
 {:bitrate=>"100", :fps=>"30", :qp=>"20"},
 {:bitrate=>"100", :fps=>"30", :qp=>"30"},
 {:bitrate=>"500", :fps=>"15", :qp=>"20"},
 {:bitrate=>"500", :fps=>"15", :qp=>"30"},
 {:bitrate=>"500", :fps=>"30", :qp=>"20"},
 {:bitrate=>"500", :fps=>"30", :qp=>"30"},
 {:bitrate=>"1000", :fps=>"15", :qp=>"20"},
 {:bitrate=>"1000", :fps=>"15", :qp=>"30"},
 {:bitrate=>"1000", :fps=>"30", :qp=>"20"},
 {:bitrate=>"1000", :fps=>"30", :qp=>"30"}]

You can also add new key to your hash.

a = {}
a[:bitrate] = ["100", "500", "1000"]
a[:fps] = ["15", "30"]
a[:qp] = ["20", "30"]
a[:bw] = [true, false]


[{:bitrate=>"100", :fps=>"15", :qp=>"20", :bw=>true},
 {:bitrate=>"100", :fps=>"15", :qp=>"20", :bw=>false},
 {:bitrate=>"100", :fps=>"15", :qp=>"30", :bw=>true},
 {:bitrate=>"100", :fps=>"15", :qp=>"30", :bw=>false},
 {:bitrate=>"100", :fps=>"30", :qp=>"20", :bw=>true},
 {:bitrate=>"100", :fps=>"30", :qp=>"20", :bw=>false},
 {:bitrate=>"100", :fps=>"30", :qp=>"30", :bw=>true},
 {:bitrate=>"100", :fps=>"30", :qp=>"30", :bw=>false},
 {:bitrate=>"500", :fps=>"15", :qp=>"20", :bw=>true},
 {:bitrate=>"500", :fps=>"15", :qp=>"20", :bw=>false},
 {:bitrate=>"500", :fps=>"15", :qp=>"30", :bw=>true},
 {:bitrate=>"500", :fps=>"15", :qp=>"30", :bw=>false},
 {:bitrate=>"500", :fps=>"30", :qp=>"20", :bw=>true},
 {:bitrate=>"500", :fps=>"30", :qp=>"20", :bw=>false},
 {:bitrate=>"500", :fps=>"30", :qp=>"30", :bw=>true},
 {:bitrate=>"500", :fps=>"30", :qp=>"30", :bw=>false},
 {:bitrate=>"1000", :fps=>"15", :qp=>"20", :bw=>true},
 {:bitrate=>"1000", :fps=>"15", :qp=>"20", :bw=>false},
 {:bitrate=>"1000", :fps=>"15", :qp=>"30", :bw=>true},
 {:bitrate=>"1000", :fps=>"15", :qp=>"30", :bw=>false},
 {:bitrate=>"1000", :fps=>"30", :qp=>"20", :bw=>true},
 {:bitrate=>"1000", :fps=>"30", :qp=>"20", :bw=>false},
 {:bitrate=>"1000", :fps=>"30", :qp=>"30", :bw=>true},
 {:bitrate=>"1000", :fps=>"30", :qp=>"30", :bw=>false}]
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