QuickLookPscript

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A Quick Look at Praat Scripting †

• This page is intended as a brief but somewhat "unorthodox" introduction to Praat scripting.
  • The primary target readers are ones who have some (partial) knowledge about programming/script language (e.g., C, perl, awk, python, VBA), and thus know, say, what array/if (conditional)/for (iteration, loop) mean. If you new to programming, see other sources*1.
  • The contents are fragmentary. For unknown commands, consult Help in Praat first. It provides you valuable information.

Table of Contents

Hello world †

1. Choose New Praat script from the Praat menu to open the ScriptEditor window.
2. Type:

   echo Hello world

3. Choose Run from the Run menu (or type C-r) to execute.

• Cf. Scripting 3.1. Hello world (official site)

Language Specification Worth Mentioning †

General †

• Output to the Info Window: echo, printline, and print
  • The three scripts below work in the same way (clearinfo clears the Info window):

    • echo Hello world

      clearinfo
      printline Hello world

      clearinfo
      print Hello world'newline$'

  • The two scripts below, however, do not work in the same way.

    • echo This is the first sentence.
      echo This is the second sentence.

      clearinfo
      printline This is the first sentence.
      printline This is the second sentence.

• Comments
  • "#" and ";" are comment characters. Praat ignores the comment characters and after them, to the end of the line.
  • Use ";" instead of "#", if you want to write a comment after a statement in the same line.

    n = 0 
    if n = 0 ;conditional
        clearinfo
        printline Hello world
    endif
    # An error occurs if ";" is replaced with "#".

    • Some commands, however, cannot be followed by a comment in the same line. For example,

      n = 0 
      if n = 0 ;conditional
          clearinfo
          printline Hello world  ; This sentence is also displayed on the Info window.
      endif

• Variable Types
  • numerics and strings
    • Variables (either numeric or string) must begin with lower cases.
    • String variables must end with $.

      str$ = "foo"
      num = 3
      ### statements below causes an error. ###
      #Str$ = "foo"  ; it begins with Upper case.
      #Num = 3
      #str = "foo"   ; it lacks $, though it has a string.

  • Arrays are also available.
    • The indices are enclosed with "[" and "]"
    • Like scalars, arrays must begin with lower cases.
    • Similarly, arrays which store strings must have $ before "["

      str$[1] = "foo"
      str$[2] = "bar"
      str$[3] = "hoge"
      str$[4] = "piyo"
      num[1] = 3
      num[2] = 34
      num[3] = 22
      num[4] = 98
      ### statements below causes an error. ###
      #str[1] = "foo"   ; it lacks $, though it has a string.
      #Num[4] = 98      ; it begins with Upper case.

  • Unfortunately, hashes (or associative arrays) are not available.

• Variable Substitution
  • Variables are substituted when put between single quotes.

    fruit$ = "apple(s)"
    count = 3
    echo I bought 'count' 'fruit$'.

    • NOTE1: No double quotations are required to literals in print (and printline and echo). Compare

      fruit$ = "apple(s)"
      count = 3
      echo "I bought" 'count' 'fruit$' "."

    • NOTE2: If the index in an array is also a variable, a dummy variable is required.

      str$[1]= "apple"
      str$[2]= "orange"
      str$[3]= "melon"
      
      clearinfo
      for i from 1 to 3
          hop$ = str$[i]   ;; a dummy variable
          printline 'i''tab$''hop$'
      endfor

• Operators
  • Comparison Operators
    • The "equal" operator is "="*2, identical with the assignment operator.

      num = 3
      str$ = "hoge"
      
      clearinfo
      if num = 3
          printline 'num'
      endif
      
      if str$ = "hoge"
          printline 'str$'
      endif

• Strings
  • Basically, operators used for numerics are also applicable to strings.
  • Interestingly, not only string "addition" (i.e., concatenation), but also string "subtraction" (i.e., truncation) is possible, using "+" and "-".

    str1$ = "abc"
    str2$ = "def"
    str3$ = "c"
    
    str4$ = str1$ + str2$
    str5$ = str1$ - str3$
    
    clearinfo
    printline 'str4$'
    printline 'str5$'

  • result:

    abcdef
    ab

• autoincrement/autodecrement operators (e.g., i++, i--) are not available.

• Conditional statements
  • if(-elsif)(-else)-endif
    • NOTE: elsif (or elif), rather than elseif and else if.

• Loops
  • for i (from m) to n-endfor, while-endwhile, repeat-until
    • from m in for can be omitted when m = 1.
    • It is not possible to decrement the loop counter in for-loop. Use while-endwhile, instead.

      n = 10
      clearinfo
      while n >= 1
          printline 'n'
          n = n-1
      endwhile

    • There seems to be no statement which escapes from the loop (break in C, or last in perl). Instead, you can substitute the loop counter (or something) with a value which does not satisfy the loop condition, for example.

      clearinfo
      max = 10
      for i to max
          if i = 5
              i = max+1      ; escape from the loop
          else
              printline 'i'
          endif
      endfor

• goto is not available. (modified July 17, 2012)

  # the "goto" command in Praat scripts
  clearinfo
  for i to 10
      if i mod 2 = 0
          goto next
      endif
      printline 'i'
      label next
  endfor

• Subroutines: procedure-endproc

• Regular expressions are available in some string functions:
  • index_regex(str$,regex$)
  • rindex_regex(str$,regex$)
  • replace_regex$(str$,regex$,substr$,n)
    • NOTE: Functions which return strings (not numerics) require $.

      str$ = "abcdefg"
      regex$ = "b[^e]*"
      clearinfo
      if index_regex(str$,regex$) <> 0
          printline match
      else
          printline not match
      endif

• Generally, index numbers start at 1 (not 0).
  • Check, for example, the value of the following string functions:
    • mid$(str$,index,len)

      str$ = "abcdefg"
      len = length(str$)
      clearinfo
      for i from 1 to len
          hop$ = mid$(str$,i,1)
          printline 'i''tab$''hop$'
      endfor

    • index(str$,substr$)

      str$ = "abcdefg"
      substr$ = "bcd"
      clearinfo
      n = index(str$,substr$)
      printline 'n'

• File IO
  • text$ < filename (read the contents of filename)

    file$ = "d:\foo.txt"
    text$ < 'file$'
    clearinfo
    print 'text$'

  • text$ > filename (make a new file and write the contents of text$)
  • text$ >> filename (add the contents of text$ to filename)

    file$ = "d:\bar.txt"
    text$ = "praat scripting is fun." + "'newline$'"
    text$ > 'file$'
    #text$ >> 'file$'

  • NOTE: Consider the use of Object, rather than "<" or ">". Very often, Object manipulation is easier and more straightforward. For Object, see below.

Particular to Praat (1): Object Manipulation †

Particular to Praat (2): form-endform †

• form and endform

Functions of ScriptEditor †

• History
• Run a script

Other ways to execute a script †

• praatcon.exe (in Windows)
• sendpraat.exe
  • scripts can be executed by using sendpraat.exe or praatcon.exe.
  • You may use option -a in praatcon.exe if you handle Unicode. (cf. Re: [praat-users] Bug in latest praatcon version (by Paul Boersma)