Return list from Delphi to python using DelphiWrapper

[hsauro 40]

I'm using DelphiWrapper to expose an API in a Delphi application that Python can run methods from. So far it works ok. It's a very primitive plugin system. My question is whether there is a way for a Delphi method to return a python list to the python caller using delphiwrapper. eg

 

In python:

mylist = delphiAPI.getlist()

 

where mylist might be a list of strings ['red', 'dog', 'rock']

 

At the moment I export two more primitive methods, one method to get the number of items and another method to get the ith item. I then create a small Python function that builds a python list using those more primitive methods. I was wondering if there was another way to do this using DelphiWrapper. In the long term, it would also be nice to return and pass to Delphi numpy arrays but I imagine that would be much more difficult. 

 

[pyscripter 689]

Wrapping of TStrings is fully supported.  You can easily turn it into a Python list if needed.   Look at Demo 31, python function testTStrings.

[hsauro 40]

That worked, thanks, I should have tried it first.

 

For those who are interested. all I did was declare my method at the Delphi end as:

 

function TObj.getlist : TStringList;

begin

  result := TStringList.Create;

  result.Add ('abc);

etc

end

 

I assume the TStringList is reference-counted at the python end and I shouldn't care about dreeing it?

 

Then at the python end, I just called

 

x = obj.getList()

 

It comes back as a TString type but you can convert it to a python list using list(x) or x.ToList(). As a TString type, it does have all the methods you'd expect for a Delphi TString type, eg 

 

x.Add ('A long string')

Edited January 26, 2022 by hsauro

[pyscripter 689]

7 hours ago, hsauro said:

 

I assume the TStringList is reference-counted at the python

Wrong assumption.  You need to call Free on the Python side or free it from Delphi.   You can examine the ownership of a Delphi object in Python using the __owned__ attribute.  If __owned__ is true it will be freed automatically.

 

When you wrap objects yourself using DelphiWrappper.Wrap, you can specify the ownership.   But here you are returning the object as a function result and you cannot tell who owns the object.   Objects returned as function results or by accessing properties are wrapped using Wrap(obj, soReference);

 

Edited January 27, 2022 by pyscripter

[hsauro 40]

Thanks, I'll take that into account

 

One other question I have, how can I check if a python script I import has a given function?  eg

 

p = Import (mypythoncode)

p.myfunction()

 

Is there a check I make to see if myfunction() is defined in mypythoncode other than actually trying to call it and trapping the exception? I should add that myfunction() isn't part of a class.

 

 

Edited January 27, 2022 by hsauro

[pyscripter 689]

2 hours ago, hsauro said:

One other question I have, how can I check if a python script I import has a given function?

Something like

 

Module := Import(ModuleName)
if Module.__dir__().Contains(FunctionName) then
   Module.FunctionName()

 

[hsauro 40]

1 hour ago, pyscripter said:

Something like

 

Module := Import(ModuleName)
if Module.__dir__().Contains(FunctionName) then
   Module.FunctionName()

 

Thanks that worked.