Difference between revisions of "User:Orso.b.schmid"

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(expand: colors)
(variable scope)
Line 11: Line 11:
 
! style="width:40%"| Vectorscript
 
! style="width:40%"| Vectorscript
 
! style="width:40%"| Python
 
! style="width:40%"| Python
|-
+
 
| Assignment operator:
+
|- style="vertical-align: top;"
 +
|  
 +
; Assignment operator:
 
| <code>:=</code>
 
| <code>:=</code>
 
| <code>=</code>
 
| <code>=</code>
|-
+
 
| Empty handle:
+
|- style="vertical-align: top;"
 +
|  
 +
; Empty brakes for functions: don't forget in python the empty brakets for routines without parameters, this rises errors that are so tricky to find.
 +
| If a routine has no parameters, it can be expressed without brakets:
 +
* <code>FSActLayer;</code>
 +
* <code>MySubroutine;</code>
 +
| If a routine has no parameters, it must be nevertheless expressed with brakets:
 +
* <code>vs.FSActLayer()</code>
 +
* <code>MySubroutine()</code>
 +
 
 +
|- style="vertical-align: top;"
 +
|
 +
; Empty handle: do pay attention also to the variable scope (see below).
 
|  
 
|  
 
* <code>h <> NIL</code>
 
* <code>h <> NIL</code>
Line 22: Line 36:
 
* <code>h != None</code>
 
* <code>h != None</code>
 
* <code>h != vs.Handle() # not inited instance of a handle, how cryptic</code>
 
* <code>h != vs.Handle() # not inited instance of a handle, how cryptic</code>
|-
+
 
| Colors:
+
|- style="vertical-align: top;"
 +
|  
 +
; Colors:
 
|
 
|
 
* Color Index:
 
* Color Index:
Line 41: Line 57:
 
* <code>vs.PenFore((65535, 0, 0)) </code> correct
 
* <code>vs.PenFore((65535, 0, 0)) </code> correct
 
* <code>vs.PenFore(65535, 0, 0) </code> fails
 
* <code>vs.PenFore(65535, 0, 0) </code> fails
|-
+
 
| Concatenate text:
+
|- style="vertical-align: top;"
 +
|  
 +
; Variable scope: perhaps the largest source of error for the vectorscripter transitioning to python
 +
|
 +
Global wins over local:
 +
* Variables must be declared
 +
* Subroutines "see" their own variables and those of any parent function/procedure where they are contained.
 +
<code lang="pas">
 +
{ GLOBAL ACCESS }
 +
{ parent of subroutine "Increment" }
 +
PROCEDURE Main;
 +
    VAR
 +
        { good praxis: label globals with "g" }
 +
        gIndex, gNum : INTEGER;
 +
   
 +
    { subroutine }
 +
    PROCEDURE Increment;
 +
        BEGIN
 +
            { gNum is not defined in this subroutine
 +
            the parser goes up to the parent container
 +
            until it finds a declaration for the var gNum.
 +
            In this case in Main }
 +
            gNum := gNum +1;
 +
            SysBeep;
 +
        END;
 +
       
 +
BEGIN
 +
    gNum := 10; { init }
 +
    FOR gIndex := 1 TO 10 DO
 +
        Increment; { increments the variable gNum }
 +
       
 +
    AlrtDialog(Concat(gNum));
 +
{ returns 20 }
 +
END;
 +
Run(Main);
 +
</code>
 +
|
 +
Local wins over global:
 +
* Variables must NOT be declared
 +
* Subroutines create automatically a local instance of any used variable.
 +
 +
<code lang="py">
 +
# LOCAL ACCESS
 +
# subroutine
 +
def Increment():
 +
    # gNum is not defined in this subroutine
 +
    # the parser creates a local instance of the var gNum!
 +
    gNum +=1
 +
    vs.SysBeep
 +
 +
gNum = 10 # init
 +
for gIndex in range(1, 10):
 +
    Increment
 +
    # increments the variable gNum
 +
    # but only inside Increment!
 +
   
 +
vs.AlrtDialog(str(gNum))
 +
# returns 10! The global var didn't set
 +
</code>
 +
 
 +
<code lang="py">
 +
# GLOBAL ACCESS
 +
# subroutine
 +
def Increment():
 +
    # gNum is not defined in this subroutine
 +
    # tell the parser that you want to edit gNum global!
 +
    global gNum
 +
    gNum +=1
 +
    vs.SysBeep()
 +
 +
gNum = 10 # init
 +
# please observe that the range is NOT 1, 10!
 +
for gIndex in range(0, 10):
 +
    Increment()
 +
    # increments the variable gNum
 +
    # but only inside Increment!
 +
   
 +
vs.AlrtDialog(str(gNum))
 +
# returns 20
 +
</code>
 +
 
 +
|- style="vertical-align: top;"
 +
|
 +
; Concatenate text:
 
|  
 
|  
 
* <code>Concat(text1, ' ', text2)</code>
 
* <code>Concat(text1, ' ', text2)</code>
 
|  
 
|  
 
* <code> text1 + ' ' + text2</code>
 
* <code> text1 + ' ' + text2</code>
|-
+
 
| Used Python version:
+
|- style="vertical-align: top;"
 +
|  
 +
; Python version:
 
|  
 
|  
 
| <code>import sys
 
| <code>import sys
Line 54: Line 155:
 
vs.Message(repr(ver))</br>
 
vs.Message(repr(ver))</br>
 
</code>
 
</code>
|-
+
 
| "import vs" yes or no?
+
|- style="vertical-align: top;"
 +
|  
 +
; "import vs" yes or no?
 
|  
 
|  
 
| <code>import vs</code> # do I need this?
 
| <code>import vs</code> # do I need this?
|-
+
 
| There is some caching going on preventing your script to reflect your changes:
+
|- style="vertical-align: top;"
 +
|  
 +
; Caching: some caching prevents your script to reflect changes:
 
|  
 
|  
 
| varPersistentPythonEngine = 412 { Boolean }
 
| varPersistentPythonEngine = 412 { Boolean }
 
In the SDK starting from VW 2014 we can read:
 
In the SDK starting from VW 2014 we can read:
 
''When True the Python engine is the same for the execution of all scripts, this solves some issues with Py_Initialize and Py_Finalize. For example, when debugging externally python leaves threas that cause crash if Py_Initialize and Py_Finalize is used for each script call. So, this allows the engine to be preserved between calls, however Vectorworks will delete all custom modules and objects defined in the engine prior each execution.''
 
''When True the Python engine is the same for the execution of all scripts, this solves some issues with Py_Initialize and Py_Finalize. For example, when debugging externally python leaves threas that cause crash if Py_Initialize and Py_Finalize is used for each script call. So, this allows the engine to be preserved between calls, however Vectorworks will delete all custom modules and objects defined in the engine prior each execution.''
|-
+
 
| Encryption:
+
|- style="vertical-align: top;"
 +
|  
 +
; Encryption:
 
| Whatever .vs or .px file is linked through your includes, will be encrypted upon running the encrypt command. More infos [[VS:Include_Files_and_Encryption| here]].
 
| Whatever .vs or .px file is linked through your includes, will be encrypted upon running the encrypt command. More infos [[VS:Include_Files_and_Encryption| here]].
 
| Create list of your included files in an xml file. Please read [https://techboard.vectorworks.net/ubbthreads.php?ubb=showflat&Number=197639&Searchpage=1&Main=39809&Words=python&Search=true#Post197639 Vlado on Techboard]
 
| Create list of your included files in an xml file. Please read [https://techboard.vectorworks.net/ubbthreads.php?ubb=showflat&Number=197639&Searchpage=1&Main=39809&Words=python&Search=true#Post197639 Vlado on Techboard]
Line 85: Line 192:
 
del months[2] # --> ['Jan', 'Feb', 'Apr', 'May', 'Jun', 'Jul']
 
del months[2] # --> ['Jan', 'Feb', 'Apr', 'May', 'Jun', 'Jul']
 
months = {1: 'Jan', 2: 'Feb', 3: 'Mar'} # --> {1: 'Jan', 2: 'Feb', 3: 'Mar'}
 
months = {1: 'Jan', 2: 'Feb', 3: 'Mar'} # --> {1: 'Jan', 2: 'Feb', 3: 'Mar'}
</code>
 
 
== Increment a var ==
 
So far I have spent a really inordinate amount of time trying to increment a counter from within a calllback routine. In VS one does it like this:
 
 
<code lang="pas">cnt := cnt +1; { variable cnt is incremented }</code>
 
 
For example:
 
 
<code lang="pas">
 
PROCEDURE Test;
 
VAR
 
    cnt : INTEGER; { variable scope here is global for this script }
 
 
    { callback subroutine fitting ForEachObject }
 
    PROCEDURE DoSomething(h: HANDLE);
 
        BEGIN
 
            { ... do something }
 
            cnt := cnt +1; { global variable is incremented }
 
        END;
 
BEGIN
 
    cnt := 0; { explicit is better than implicit :) }
 
    ForEachObject(DoSomething, (ALL)); { pick objects by criteria, there the variable cnt will increment }
 
    AlrtDialog(Concat('Did something ', cnt, ' times.'));
 
END;
 
Run(Test);
 
</code>
 
 
How do I get this done in Python? It's not as easy as it looks like. I thought that this would work:
 
 
<code lang="py">cnt += 1</code>
 
 
For example:
 
 
<code lang="py">
 
import vs;
 
cnt = 0 # explicit is better than implicit :)
 
 
def DoSomething(h):
 
    # ... do something
 
    cnt += 1 # variable should be incremented
 
 
vs.ForEachObject(DoSomething, '(ALL)')  # pick objects by criteria, there the variable cnt will increment
 
vs.AlrtDialog(vs.Concat('Did something ', cnt, ' times.'))
 
</code>
 
 
Error: UnboundLocalError: local variable can't be referenced before assignment
 
 
But it doesn't work from within '''DoSomething''' and I can't turn DoSomething into a function outputting an integer, otherwise it won't fit the required callback syntax expected by [[VS:ForEachObject| ForEachObject]]
 
 
Searching the web I found out that I am not alone in this misery. See [http://www.reddit.com/r/Python/comments/wbs1o/best_way_to_increment_of_1_in_python this], LOL. This comment wins, on my opinion: "We can make Python ask Perl to ask C."
 
 
Now I'll try this mysterious approach treating the variable as a list (http://bytes.com/topic/python/answers/46419-how-does-one-write-function-increments-number source):
 
<code lang="py">
 
def incr(counters): counters[0] += 1
 
 
counters =[100]
 
incr(counters)
 
print counters [101]
 
 
</code>
 
</code>

Revision as of 02:45, 19 May 2015

Ciao,

I am Orso, an Italian Vectorscripter since many years. Some of you might know me from Vectorlab or the comments on the present Developer wiki. I feel very comfortable with Vectorscript (from now on: VS) but will now switch over to Python for even more power. I will try to share here comments, problems -and solutions- from the point of view of a non-programmer. --Orso.b.schmid (talk) 08:13, 17 May 2015 (EDT)

If you add comments, please use the full wiki formatting, easily available clicking on Advanced while on edit mode and don't forget to sign up your comment using --~~~~!

VS <> Py FAQ

Description Vectorscript Python
Assignment operator
:= =
Empty brakes for functions
don't forget in python the empty brakets for routines without parameters, this rises errors that are so tricky to find.
If a routine has no parameters, it can be expressed without brakets:
  • FSActLayer;
  • MySubroutine;
If a routine has no parameters, it must be nevertheless expressed with brakets:
  • vs.FSActLayer()
  • MySubroutine()
Empty handle
do pay attention also to the variable scope (see below).
  • h <> NIL
  • h != None
  • h != vs.Handle() # not inited instance of a handle, how cryptic
Colors
  • Color Index:
    SetPenFore(h, RGBToColorIndex(65535, 0, 0));
    PenFore(RGBToColorIndex(65535, 0, 0));
  • RGB:
    SetPenFore(h, 65535, 0, 0);
  • Color Index:
    vs.SetPenFore(h, vs.RGBToColorIndex(65535, 0, 0))
  • RGB in Tuple:
    vs.SetPenFore(h, (65535, 0, 0))
  • Hex in Tuple:
    vs.SetPenFore(h, (0xFFFF, 0, 0))

Warning: don't forget the brakets:

  • vs.PenFore((65535, 0, 0)) correct
  • vs.PenFore(65535, 0, 0) fails
Variable scope
perhaps the largest source of error for the vectorscripter transitioning to python

Global wins over local:

  • Variables must be declared
  • Subroutines "see" their own variables and those of any parent function/procedure where they are contained.
{ GLOBAL ACCESS }
{ parent of subroutine "Increment" }
PROCEDURE Main;
    VAR
        { good praxis: label globals with "g" }
        gIndex, gNum : INTEGER; 
    
    { subroutine }
    PROCEDURE Increment;
        BEGIN
            { gNum is not defined in this subroutine 
            the parser goes up to the parent container 
            until it finds a declaration for the var gNum.
            In this case in Main }
            gNum := gNum +1;
            SysBeep;
        END;
        
BEGIN
    gNum := 10; { init }
    FOR gIndex := 1 TO 10 DO
        Increment; { increments the variable gNum }
        
    AlrtDialog(Concat(gNum));
{ returns 20 }
END;
RUN(Main);

Local wins over global:

  • Variables must NOT be declared
  • Subroutines create automatically a local instance of any used variable.
# LOCAL ACCESS
# subroutine
def Increment():
    # gNum is not defined in this subroutine
    # the parser creates a local instance of the var gNum!
    gNum +=1
    vs.SysBeep
 
gNum = 10 # init
for gIndex in range(1, 10):
    Increment 
    # increments the variable gNum
    # but only inside Increment!
    
vs.AlrtDialog(str(gNum))
# returns 10! The global var didn't set
# GLOBAL ACCESS
# subroutine
def Increment():
    # gNum is not defined in this subroutine
    # tell the parser that you want to edit gNum global!
    global gNum
    gNum +=1
    vs.SysBeep()
 
gNum = 10 # init
# please observe that the range is NOT 1, 10!
for gIndex in range(0, 10):
    Increment()
    # increments the variable gNum
    # but only inside Increment!
    
vs.AlrtDialog(str(gNum))
# returns 20
Concatenate text
  • Concat(text1, ' ', text2)
  • text1 + ' ' + text2
Python version
import sys

ver = sys.version_info
vs.Message(repr(ver))

"import vs" yes or no?
import vs # do I need this?
Caching
some caching prevents your script to reflect changes:
varPersistentPythonEngine = 412 { Boolean }

In the SDK starting from VW 2014 we can read: When True the Python engine is the same for the execution of all scripts, this solves some issues with Py_Initialize and Py_Finalize. For example, when debugging externally python leaves threas that cause crash if Py_Initialize and Py_Finalize is used for each script call. So, this allows the engine to be preserved between calls, however Vectorworks will delete all custom modules and objects defined in the engine prior each execution.

Encryption
Whatever .vs or .px file is linked through your includes, will be encrypted upon running the encrypt command. More infos here. Create list of your included files in an xml file. Please read Vlado on Techboard

Lists

Lists are powerful in Python, below some fascinating lists manipulations. They remind me of Applescript:

months = "Jan Feb Mar Apr May Jun Jul"
months = months.split() # no splitter defined and it will use the empty space --> ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul']
months[2] # --> 'Mar' note that the index is 0-based
months2 = "Jan, Feb, Mar, Apr, May, Jun, Jul"
months2.split(', ') # --> ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul'] use comma and empty space as splitter 
months.append('Jul') # --> ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul'] append adds an item to a list 
months.pop() #- -> 'Jul' pop fetches the last item of a list
', sunny '.join(months) # --> ', sunny Jan, sunny Feb, sunny Mar, sunny Apr, sunny May, sunny Jun, sunny Sep'
'-'.join(months[1:3]) # --> 'Feb-Mar'
del months[2] # --> ['Jan', 'Feb', 'Apr', 'May', 'Jun', 'Jul']
months = {1: 'Jan', 2: 'Feb', 3: 'Mar'} # --> {1: 'Jan', 2: 'Feb', 3: 'Mar'}
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