Backup of QuickLookPscript(No. 10)

FrontPage

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

A Quick Look at Praat Scripting

↑

Hello world †

Choose New Praat script from the Praat menu to open the ScriptEditor window.
Type:
```
echo Hello world
```
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 †

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*2.
```
# Hello word script in Praat
echo Hello world   ; write to the Info window
## NOTE: An error occurs if ";" is replaced with "#"
```

Output to the Info Window: echo, printline, and print

The three scripts below work in the same way:

echo Hello world

clearinfo  ; clears the Info window
printline Hello world

clearinfo
print Hello world'newline$'

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 "="*3, 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.

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 (if any), rather than "<" or ">". Very often, Object manipulation is easier and more straightforward. For Object, see below.

↑

Particular to Praat (1): form-endform †

form and endform

↑

Particular to Praat (2): Object Manipulation †

Those who conquer object manipulation techniques conquer Praat scripting. (The present author)

↑

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)

Backup of QuickLookPscript (No. 10)