Python under Moon light

After reading this post I thought of comparing the performance of python against the lightweight scripting language Lua. So to have a fair comparison I ported the MorseCode encoder/decoder wirtten in python into a Lua script with no change to the logic or the sequence.

--morse code table
codes = {
['!'] = "-.-.--", [' '] = "|", ['"'] = ".-..-.", ['$'] = "...-..-",
['\''] = ".----.", ['&'] = ".-...", [')'] = "-.--.-", ['('] = "-.--.",
['+'] = ".-.-.", ['-'] = "-....-", [','] = "--..--", ['/'] = "-..-.",
['.'] = ".-.-.-", ['1'] = ".----", ['0'] = "-----", ['3'] = "...--",
['2'] = "..---", ['5'] = ".....", ['4'] = "....-", ['7'] = "--...",
['6'] = "-....", ['9'] = "----.", ['8'] = "---..", [';'] = "-.-.-",
[':'] = "---...", ['='] = "-...-", ['?'] = "..--..", ['A'] = ".-",
['@'] = ".--.-.", ['C'] = "-.-.", ['B'] = "-...", ['E'] = ".",
['D'] = "-..", ['G'] = "--.", ['F'] = "..-.", ['I'] = "..",
['H'] = "....", ['K'] = "-.-", ['J'] = ".---", ['M'] = "--",
['L'] = ".-..", ['O'] = "---", ['N'] = "-.", ['Q'] = "--.-",
['P'] = ".--.", ['S'] = "...", ['R'] = ".-.", ['U'] = "..-",
['T'] = "-", ['W'] = ".--", ['V'] = "...-", ['Y'] = "-.--",
['X'] = "-..-", ['Z'] = "--..", ['_'] = "..--.-"
}


binary = {['.']="10",['-']="1110",[',']="000",['|']="0000000"}


function encode(value)
    --encodes the value into morse code
    value = string.upper(value)
    value = string.gsub(value,'%*', 'X')
    value = string.gsub(value,'%^', 'XX')
    local morse_value=""
    local length = string.len(value)
    local i = 1
    while i <= length do
     local chr = string.sub(value,i,i)
        if chr then
           morse_value = morse_value .. codes[chr] .. ","
        end
        i = i + 1
    end
    return _get_binary(morse_value)
end

function _get_binary(value)
     local binary_value = ""
     local length = string.len(value)
     local i = 1
     while i <= length do
         local chr = string.sub(value,i,i)
         if chr then
            binary_value = binary_value .. binary[chr]
         end
         i = i + 1
     end
     return binary_value
end

function decode(morse_code_value)
    -- decodes the morse bytes
    decoded_value = _decode_binary(morse_code_value)
    ascii_value=""
    for w in string.gfind(decoded_value, "[-.|]+") do
      ascii_value = ascii_value .. _get_key(w)
    end
    return ascii_value
end

function _get_key(value)
     --returns the key for the given value
     for k, v in next, codes do
         if v == value then
            return k
         end
     end
     return ''
end

function _decode_binary(binary)
    dah_replaced = string.gsub(binary,'1110', '-')
    dit_replaced = string.gsub(dah_replaced,'10', '.')
    comma_replaced = string.gsub(dit_replaced,'000', ',')
    zero_replaced = string.gsub(comma_replaced,'0', '|,')
    return zero_replaced
end

function print_usage()
 print("Usage : "..arg[0].." [d (decode) |e (encode)] [input string]")
end


if arg[1] == nil then
 print_usage()
else
 if arg[1] == 'd' then
  print("Decoded value : "..decode(arg[2]))
 elseif arg[1] == 'e' then
  if arg[2] == nil then
   print_usage()
  else
   print("Encoded value : "..encode(arg[2]))
  end
 else
  print("Encoded value : "..encode(arg[1]))
 end
end

The Lua script was much faster than the python one. May be i have not written the python script in an optimistic way, but logic remains the same.

Aanand Natarajan@AANAND /h/MorseEnDecode/src
$ time python MorseEnDecode.py aanand
encoding
Encoded : 10111000010111000011101000010111000011101000011101010000

real 0m0.140s
user 0m0.015s
sys 0m0.015s

Aanand Natarajan@AANAND /h/MorseEnDecode/src
$ time lua MorseEnDecode.lua aanand
Encoded value : 10111000010111000011101000010111000011101000011101010000

real 0m0.031s
user 0m0.015s
sys 0m0.015s

Look at the real time which is 0.140 seconds for the Python version and 0.31 seconds for the Lua version.
This doesn't mean Python is not fast. I like Python as a language, for its features and its highly performant comparing against many other scripting languages.