Help on hashing multiple keys and values

Ruby
1

I’m trying to create a hash with multiple values per key from a tab
delimited file. numbers_and_colors.txt example:

1 Red
2 Blue
3 Red
2 Green

What I need is a hash that has key 2 assigned to values Blue and Green.
Running what I have below just erases the previous key, so puts
name_hash[“2”] would only show Green. Ruby example:

name_hash = Hash.new
File.open(“numbers_and_colors.txt”).each do |file_line|
file_line.chomp!
line_parts = file_line.split(/\t/)
name_hash["#{line_parts[0]}"] = “#{line_parts[1]}”

I need this in a hash, so is there another way to go about this? Thanks
in advance to any help, as you can probable tell I only started learning
Ruby recently.

2

On 04/14/11 09:33, Adam Adam wrote:

name_hash[“2”] would only show Green. Ruby example:

name_hash = Hash.new
File.open(“numbers_and_colors.txt”).each do |file_line|
file_line.chomp!
line_parts = file_line.split(/\t/)
name_hash["#{line_parts[0]}"] = “#{line_parts[1]}”

I need this in a hash, so is there another way to go about this? Thanks
in advance to any help, as you can probable tell I only started learning
Ruby recently.

The idiom I use is to add an array to hold the values, like this:

(name_hash[key] ||= []) << value

Clifford H…

3

Adam Adam wrote in post #992620:

I’m trying to create a hash with multiple values per key from a tab
delimited file. numbers_and_colors.txt example:

The idiom I use is to add an array to hold the values, like this:

(name_hash[key] ||= []) << value

hi adam -

i do what clifford does, but since i’m thick-headed i do it a bit more
verbosely (is that a word?)…

foo = Hash.new{|key, value| key[value] = []}

this sets up a hash, where each key’s value is an array (you can also
get all crazy, and make each value a hash…) once you’ve got that set,
play around with this kind of stuff…

foo [“rays”] = %W[alpha beta gamma]
foo [“planets”] = %W[mercury venus earth mars]
foo [“colors”] = %W[red orange yellow green blue indigo violet]

p foo
p foo.length
p foo [“rays”][1]
p foo [“planets”][-1]
p foo [“colors”].length

  • j
4

On 04/14/11 10:46, Adam Adam wrote:

I end up with
“Blue”
“Blue”
“Green”

I’m worried with the actual data this will be 100000 “Blue” and a
“Green”. Thanks for the help.

You shouldn’t print the data until you finish processing the file.
You don’t need to use “#{some-string}” to make a string into a string,
and I’ve no idea what you’re attempting by using %W[…].
You didn’t seem to understand or apply the pattern I suggested.

Basically it says: Find this array in the hash (if it doesn’t exist
then initialize it with an empty array) and append this word to the
array.

Try the following program (which contains the data file), understand
it, and if there’s something you don’t follow, come back and ask again.
The output it gives is this:

{1=>[“Red”], 2=>[“Blue”, “Green”], 3=>[“Red”]}

If you want to arrange for the entries in each array to be unique,
you’ll need to add that somehow, this doesn’t do it:

name_hash = {}
DATA.each do |file_line|
line_parts = file_line.split(/\W+/)
(name_hash[line_parts[0].to_i] ||= []) << line_parts[1]
end

p name_hash
END
1 Red
2 Blue
3 Red
2 Green

5

Hi Clifford and Jake,

There must be something I’m missing, when I run

name_hash = Hash.new{|key, value| key[value] = []}
File.open(“numbers_and_colors.txt”).each do |file_line|
file_line.chomp!
line_parts = file_line.split(/\t/)
name_hash["#{line_parts[0]}"] = %W["#{line_parts[1]}"]
puts name_hash[“2”]
end

I end up with
“Blue”
“Blue”
“Green”

I’m worried with the actual data this will be 100000 “Blue” and a
“Green”. Thanks for the help. And according to Merriam-Webster verbosely
is indeed a word

-Adam

6

Clifford H. wrote in post #992634:

You don’t need to use “#{some-string}” to make a string into a string,

haha, i scabbed this together from something else! there’s a lot of
unnecessary weirdness going on… this works just as well of course:

hash [parts[0]] << parts[1]

-j

7

hey adam -

think i finally figured out what you were trying to do - sorry for not
reading your first post a little more carefully… try this:

hash = Hash.new{|key, value| key[value] = []}
file = File.open(“hashtext.txt”, ‘r’)
file.each do |line|
line.chomp!
parts = line.split(/\t/)
hash ["#{parts[0]}"] << “#{parts[1]}”
end
file.close

p hash[“1”]
p hash [“2”]
p hash [“3”]

=> [“red”]
[“blue”, “green”]
[“red”]

ah, and %W is just a nice way of saving on putting everything in
quotes if you’re making an array of strings…
array = %W[chunky bacon] ## notice no commas between entries
is the same as
array = [“chunky”, “bacon”]

  • j
8

Adam Adam wrote:

name_hash[“2”] would only show Green. Ruby example:

name_hash = Hash.new
File.open(“numbers_and_colors.txt”).each do |file_line|
file_line.chomp!
line_parts = file_line.split(/\t/)
name_hash["#{line_parts[0]}"] = “#{line_parts[1]}”

I need this in a hash, so is there another way to go about this? Thanks
in advance to any help, as you can probable tell I only started learning
Ruby recently.

name_hash = {}
name_hash.default = []
IO.foreach( “data2” ){|line|
key, val = line.split
name_hash[ key ] += [val]
}
p name_hash

==>

{“1”=>[“Red”], “2”=>[“Blue”, “Green”], “3”=>[“Red”]}

9

Jake and Clifford,

Both methods work wonderfully, thanks for the help, this was bothering
me for 2 hours. Sorry for the bother, Clifford, I tried your first
suggestion, but I had no idea about the necessary <<. Thanks again,
much appreciated!

Adam