Asp Forum - How to improve this code?

Jair Rillo junior

1/23/2008 1:06:00 AM

Hi guys,
I am new in the Ruby world, I am coming from Java, and I would like to
"think " in Ruby instead Java.

I did a code to read a CSV file (separated by comma), organize the
values and print the output.

Basically the CSV looks like this:
bla@bla.com,value1
bla@bla.com,value2
bla@bla.com,value3
bla@bla.com,value4
ruby@ruby.br,value1
ruby@ruby.br,value2

the output should be in two lines
bla@bla.com,value1,value2,value3,value4
ruby@ruby.br,value1,value

My initial thought was store the values into a Hash object, where the
KEY is the email (column a) and the value is an Array containing the
values (column b).
Going through all lines, test if the email address already exists in the
Hash, if so update the Array, otherwise create a new entry into the
Hash.

The code following below:

h = Hash.new
File.open("Sector_brand.csv").each_line do |lines|
values = lines.split(",")
email = values[0]
content = values[1]
if h.key?(email)
l = h[email]
l.push content
h[email] = l
else
l = [content]
h[email] = l
end
end

I didn't put the code to print the Hash. Also I didn't create the code
above in a class because it is just a test.

Well guys, does anyone could see my code and give comments? How the code
above could be improved?

Thanks in advice.

Junior
--
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15 Answers

7stud --

1/23/2008 1:49:00 AM

Jair Rillo Junior wrote:
> Hi guys,
> I am new in the Ruby world, I am coming from Java, and I would like to
> "think " in Ruby instead Java.
>
> I did a code to read a CSV file (separated by comma), organize the
> values and print the output.
>
> Basically the CSV looks like this:
> bla@bla.com,value1
> bla@bla.com,value2
> bla@bla.com,value3
> bla@bla.com,value4
> ruby@ruby.br,value1
> ruby@ruby.br,value2
>
> the output should be in two lines
> bla@bla.com,value1,value2,value3,value4
> ruby@ruby.br,value1,value
>
> My initial thought was store the values into a Hash object, where the
> KEY is the email (column a) and the value is an Array containing the
> values (column b).
> Going through all lines, test if the email address already exists in the
> Hash, if so update the Array, otherwise create a new entry into the
> Hash.
>
> The code following below:
>
> h = Hash.new
> File.open("Sector_brand.csv").each_line do |lines|
> values = lines.split(",")
> email = values[0]
> content = values[1]
> if h.key?(email)
> l = h[email]
> l.push content
> h[email] = l
> else
> l = [content]
> h[email] = l
> end
> end
>
> I didn't put the code to print the Hash. Also I didn't create the code
> above in a class because it is just a test.
>
> Well guys, does anyone could see my code and give comments? How the code
> above could be improved?
>
> Thanks in advice.
>
> Junior

Try this:

h = Hash.new do |hash, key|
hash[key] = []
end

IO.foreach('data.txt') do |line|
data = line.chomp.split(',')
h[data[0]] << data[1]
end

p h

--output:--
{"ruby@ruby.br"=>["value1", "value2"], "bla@bla.com"=>["value1",
"value2", "value3", "value4"]}
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Radoslaw Bulat

1/23/2008 1:51:00 AM

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cmJvc2UgYW5kCmxlc3MgdHlwaW5nKSBhYm92ZSAicHVzaCIsIHNvOgoKaFtlbWFpbF0gPDwgY29u
dGVudAoKLS0gClJhZG9zs2F3IEJ1s2F0CgpodHRwOi8vcmFkYXJlay5qb2dnZXIucGwgLSBt82og
YmxvZwo=

John Carter

1/23/2008 2:37:00 AM

On Wed, 23 Jan 2008, Jair Rillo Junior wrote:

> Hi guys,
> I am new in the Ruby world, I am coming from Java, and I would like to
> "think " in Ruby instead Java.
>
> I did a code to read a CSV file (separated by comma), organize the
> values and print the output.

Probably the mostly useful first thought in Ruby is... "Nah, I bet
it's in the standard library somewhere, better check ruby-doc.org"

From standard library module 'csv'

# Open a CSV formatted file for reading or writing.
#
# For reading.
#
# EXAMPLE 1
# CSV.open('csvfile.csv', 'r') do |row|
# p row
# end
#
# EXAMPLE 2
# reader = CSV.open('csvfile.csv', 'r')
# row1 = reader.shift
# row2 = reader.shift
# if row2.empty?
# p 'row2 not find.'
# end
# reader.close
#
# ARGS
# filename: filename to parse.
# col_sep: Column separator. ?, by default. If you want to separate
# fields with semicolon, give ?; here.
# row_sep: Row separator. nil by default. nil means "\r\n or \n". If you
# want to separate records with \r, give ?\r here.
#
# RETURNS
# reader instance. To get parse result, see CSV::Reader#each.
#
#
# For writing.
#
# EXAMPLE 1
# CSV.open('csvfile.csv', 'w') do |writer|
# writer << ['r1c1', 'r1c2']
# writer << ['r2c1', 'r2c2']
# writer << [nil, nil]
# end
#
# EXAMPLE 2
# writer = CSV.open('csvfile.csv', 'w')
# writer << ['r1c1', 'r1c2'] << ['r2c1', 'r2c2'] << [nil, nil]
# writer.close
#
# ARGS
# filename: filename to generate.
# col_sep: Column separator. ?, by default. If you want to separate
# fields with semicolon, give ?; here.
# row_sep: Row separator. nil by default. nil means "\r\n or \n". If you
# want to separate records with \r, give ?\r here.
#
# RETURNS
# writer instance. See CSV::Writer#<< and CSV::Writer#add_row to know how
# to generate CSV string.
#

> My initial thought was store the values into a Hash object, where the
> KEY is the email (column a) and the value is an Array containing the
> values (column b).
> Going through all lines, test if the email address already exists in the
> Hash, if so update the Array, otherwise create a new entry into the
> Hash.

My flavourite idiom is...
require 'set'
h = Hash.new{|hash,key| hash[key] = Set.new}

then in the loop..
values = lines.split(",")
email = values.shift
h[email].merge(values)

Ooh... That's just sooo pretty!

John Carter Phone : (64)(3) 358 6639
Tait Electronics Fax : (64)(3) 359 4632
PO Box 1645 Christchurch Email : john.carter@tait.co.nz
New Zealand

Clifford Heath

1/23/2008 4:55:00 AM

The others have shown you how to create a Hash with a block to provide
a default value. Another way to program this is to say:

File.open("Sector_brand.csv").each_line do |lines|
values = lines.split(",")
(h[values[0]] ||= []) << values[1]
end

....or the equivalent using one of the CSV libraries.

Clifford Heath.

botp

1/23/2008 5:29:00 AM

On Jan 23, 2008 9:05 AM, Jair Rillo Junior <jrjuniorsp@yahoo.com.br> wrote:
> My initial thought was store the values into a Hash object, where the

my initial thought was just to output them plainly :)
my stupid example follows,

botp@pc4all:~$ cat test.rb
v0=nil
File.open("test.txt").each_line do |lines|
values = lines.chomp.split(",")
if v0 != values[0]
puts unless v0.nil?
v0 = values[0]
print v0
end
print ",",values[1]
end

botp@pc4all:~$ ruby test.rb
bla@bla.com,value1,value2,value3,value4
ruby@ruby.br,value1,value2

7stud --

1/23/2008 6:05:00 AM

John Carter wrote:
>
> Probably the mostly useful first thought in Ruby is... "Nah, I bet
> it's in the standard library somewhere, better check ruby-doc.org"
>

I disagree with that. In my experience if you can avoid the Ruby
Standard library, you will save yourself a lot of headaches because it
is so poorly documented, and your code will probably run faster as well.

> From standard library module 'csv'

In particular, the csv module is so inefficient, James Gray wrote his
own module and called it fastercsv.
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William James

1/23/2008 7:29:00 AM

On Jan 22, 7:05 pm, Jair Rillo Junior <jrjunio...@yahoo.com.br> wrote:
> Hi guys,
> I am new in the Ruby world, I am coming from Java, and I would like to
> "think " in Ruby instead Java.
>
> I did a code to read a CSV file (separated by comma), organize the
> values and print the output.
>
> Basically the CSV looks like this:
> b...@bla.com,value1
> b...@bla.com,value2
> b...@bla.com,value3
> b...@bla.com,value4
> r...@ruby.br,value1
> r...@ruby.br,value2
>
> the output should be in two lines
> b...@bla.com,value1,value2,value3,value4
> r...@ruby.br,value1,value

awk -F, "{a[$1]=a[$1] FS $2} END{for(k in a)print k a[k]}" file

Stephane Wirtel

1/23/2008 8:19:00 AM

You can try this code

#!/usr/bin/env ruby

require "csv"

hash = Hash.new { |hash,key| hash[key] = [] }

CSV.open( "file.csv", "r", "," ) do |row|
hash[row[0]] << row[1]
end

Good luck

Stephane

Jair Rillo junior

1/23/2008 11:03:00 AM

Hey guys, so many ways to do !!!

I didn't know about csv library, as well as I didn't know about the <<
operator.

Thank you very much guys!!

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Lee Jarvis

1/23/2008 12:14:00 PM

Jair Rillo Junior wrote:
> Hey guys, so many ways to do !!!
>
> I didn't know about csv library, as well as I didn't know about the <<
> operator.

Yeah its actually a method.. Array#<<

it seems to be prefered over Array#push, although they both return the
array itself so you can string along a load of appending values
together..

>> foo = [1,2]
=> [1, 2]
>> foo << 3 << 4
=> [1, 2, 3, 4]
>> foo.push(5,6)
=> [1, 2, 3, 4, 5, 6]
>> foo.push(7).push(8)
=> [1, 2, 3, 4, 5, 6, 7, 8]

Regards,
Lee
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comp.lang.ruby

How to improve this code?

Jair Rillo junior

7stud --

Radoslaw Bulat

John Carter

Clifford Heath

botp

7stud --

William James

Stephane Wirtel

Jair Rillo junior

Lee Jarvis

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