Replace a number with another number.

Question

Consider a list of numbers:

1
2
3
17
8
9
23
...etc.

I want to replace these numbers with another number, based on another list:

1001=1
1002=2
1003=3
1004=8
1005=23
1006=9
1007=17

What is the quickest way to do this? (like using regular expression in Notepad++, etc.)

Answer 1

Put your mappings into an array (or a dictionary, depending on how your numbers are, such that):

map[oldvalue] = newvalue;

Then iterate over the original list and replace, eg:

oldlist = '1\n2\n3\n17'
map = {'1' : '1001', '2': '1002', '3' : '1003', '17' : '1007'}

result = ''
for num in oldlist.split('\n'):
    result += map[num] + '\n'

See it on ideone

Answer 2

I do this kind of thing in perl -- something like

%replacements = (1=>1001, 2=>1002, 3=>1003 );
while (<>) {
   chomp;
   @nums = split(/ /);
   @outnums = ();
   foreach $n (@nums) {
       $outnums[$#outnums + 1] = $replacements{$n};
   }
   print join(' ', @outnums)."\n";
}

then run

perl scriptname.pl < infile > outfile

Answer 3

You don't want a regex since you need to somehow map the numbers to their replacements. Here's a script in Ruby:

Given a file called 'nums' like so:

1
2
3

...and so on...

map = {
  1 => 1000,
  2 => 2000,
  ...etc...
}
results = File.open('output','a')
File.open('nums').readlines.each do |line|
  results.write( map[line.to_i].to_s + "\n" ) if map.has_key?(line.to_i)
end

Run this like: ruby thescript.rb and the file 'output' now has your new number set.