The Wiert Corner – irregular stream of stuff

Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for the ‘Conferences’ Category

Python – list transformation; string formatting – Stack Overflow

Posted by jpluimers on 2020/01/08

Sometimes simple examples are the best: [WayBack] Python – list transformation – Stack Overflow.

Interactive example (note you can run and save at repl.it in either [WayBack] Repl.it – Python 3 or [WayBack] Repl.it – Python 2; you can run but not save it at [WayBack] Welcome to Python.org: interactive Python shell):

# Links the documentation are Python 2, though everything works in Python 3 as well.

x = [1,2,3,4,5,11]
print("x: ", repr(x))

y = ['01','02','03','04','05','11']
print("y: ", repr(y))

# List comprehension https://docs.python.org/2/tutorial/datastructures.html#list-comprehensions
# ... using `str.format()` (Python >= 2.6): https://docs.python.org/2/library/stdtypes.html#str.format and https://docs.python.org/2/library/string.html#formatstrings
y = ["{0:0>2}".format(v) for v in x]
print("y: ", repr(y))

# ... using the traditional `%` formatting operator (Python < 2.6): https://docs.python.org/2/library/stdtypes.html#string-formatting y = ["%02d" % v for v in x] print("y: ", repr(y)) # ... using the format()` function (Python >= 2.6): https://docs.python.org/2/library/functions.html#format and https://docs.python.org/2/library/string.html#formatstrings
# this omits the "{0:...}" ceremony from the positional #0 parameter
y = [format(v, "0>2") for v in x]
print("y: ", repr(y))

# Note that for new style format strings, the positional argument (to specify argument #0) is optional (Python >= 2.7) https://docs.python.org/2/library/string.html#formatstrings
y = ["{:0>2}".format(v) for v in x]
print("y: ", repr(y))

# Using `lambda`
# ... Python < 3 return a list y = map(lambda v: "%02d" %v, x) print("y: ", repr(y)) # ... Python >= 3 return a map object to iterate over https://stackoverflow.com/questions/1303347/getting-a-map-to-return-a-list-in-python-3-x/1303354#1303354
y = list(map(lambda v: "%02d" %v, x))
print("y: ", repr(y))

Output:

Python 3 Python 2
Python 3.6.1 (default, Dec 2015, 13:05:11)
[GCC 4.8.2] on linux
   
x:  [1, 2, 3, 4, 5, 11]
y:  ['01', '02', '03', '04', '05', '11']
y:  ['01', '02', '03', '04', '05', '11']
y:  ['01', '02', '03', '04', '05', '11']
y:  ['01', '02', '03', '04', '05', '11']
y:  ['01', '02', '03', '04', '05', '11']
y:  <map object at 0x7fe1218200b8>
y:  ['01', '02', '03', '04', '05', '11']
Python 2.7.10 (default, Jul 14 2015, 19:46:27)
[GCC 4.8.2] on linux
   
('x: ', '[1, 2, 3, 4, 5, 11]')
('y: ', "['01', '02', '03', '04', '05', '11']")
('y: ', "['01', '02', '03', '04', '05', '11']")
('y: ', "['01', '02', '03', '04', '05', '11']")
('y: ', "['01', '02', '03', '04', '05', '11']")
('y: ', "['01', '02', '03', '04', '05', '11']")
('y: ', "['01', '02', '03', '04', '05', '11']")
('y: ', "['01', '02', '03', '04', '05', '11']")

–jeroen

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Posted in Conference Topics, Conferences, Development, Event, Python, Scripting, Software Development | Leave a Comment »

TFreedObject in FastMM4/FastMM4.pas at master · pleriche/FastMM4 · GitHub

Posted by jpluimers on 2020/01/08

Reminder to Self:

  {The class used to catch attempts to execute a virtual method of a freed
   object}
  TFreedObject = class
  public
    procedure GetVirtualMethodIndex;
    procedure VirtualMethodError;
{$ifdef CatchUseOfFreedInterfaces}
    procedure InterfaceError;
{$endif}
  end;

If you encounter the class TFreedObject when doing a cast, then you’re working on a freed object and have FastMM4 enabled to detect that.

Source: [WayBackFastMM4/FastMM4.pas at master · pleriche/FastMM4 · GitHub; FastMM4 – A memory manager for Delphi and C++ Builder with powerful debugging facilities

Note that if you want to see the underlying FastMM data for any TObject allocation, use this watch (where Self is the current instance):

PFullDebugBlockHeader(PByte(Self) - SizeOf(TFullDebugBlockHeader))^

You can also put a ,r behind it to see the fields of this structure:

(Reserved1:nil; Reserved2:nil; AllocatedByRoutine:$41BF74; AllocationGroup:0; 
AllocationNumber:592682; 
AllocationStackTrace:(4224198, 4233131, 4235210, 11103806, 6552132, 131126, 6597961, 11106984, 4235210, 11107153, 11104090); 
AllocatedByThread:90428; FreedByThread:90428; 
FreeStackTrace:(4241541, 131126, 4235210, 11103806, 6552132, 131126, 6597961, 11106984, 4235210, 11107153, 11104090); 
UserSize:36; PreviouslyUsedByClass:132272; HeaderCheckSum:2673350594)

–jeroen

Posted in Conference Topics, Conferences, Delphi, Development, Event, Software Development | Leave a Comment »

Using a main check __main__ to call a main function in Python

Posted by jpluimers on 2020/01/01

[WayBack] __main__ — Top-level script environment — Python 3 documentation recommends code like this:

if __name__ == "__main__":
    # execute only if run as a script
    main()

This has many cool possibilities, including these that I like most as a beginning Python developer:

  • having your def main(): function in a separate source file
  • allowing to return prematurely from your main function (you cannot do this from the main block)
  • allowing a file to distinguish if it is being loaded as a module, or as a main program

Related:

–jeroen

Posted in Conference Topics, Conferences, Development, Event, Python, Scripting, Software Development | Leave a Comment »

Delphi multi-threading: confused by TThread.Synchronize / TThread.Queue? You’re not alone. And you need to be aware of exceptions there too.

Posted by jpluimers on 2020/01/01

Below an elaboration on my answer to the question [WayBack] I don’t understand the following part of the second Delphi example:TThread.Synchronize… – Alberto Paganini – Google+:

I was looking at the Task example at the EMB wiki link below

http://docwiki.embarcadero.com/RADStudio/Tokyo/en/Tutorial:_Using_Tasks_from_the_Parallel_Programming_Library

and I don’t understand the following part of the second Delphi example:

TThread.Synchronize(nil,
  procedure
  begin
    Label1.Text := lValue.ToString;
  end);

why is there the need to pass Label1.Text := lValue.ToString; as procedure in TThread.Synchronize ?

Why not a simple Label1.Text := lValue.ToString; ?

Basically that question can be either of these:

  1. Why is there no easier language construct than wrapping the callback in a procedure (anonymous method).
  2. Why a call to TThread.Synchronize at all?

The tutorial that Alberto refers to is [WayBack] Tutorial: Using Tasks from the Parallel Programming Library – RAD Studio. That example uses the TTask feature in Delphi, but the portion he has a question about is general to any multi-treading in Delphi that touches the updating of a VCL or FMX UI from another thread.

This is the more complete code in the meant example:

procedure TForm1.ButtonTask1Click(Sender: TObject);
var
  lValue: Integer;
begin
    Label1.Text := '--';
    TTask.Run(procedure
      begin
          {Some calculation that takes time}
          Sleep(3000);
          lValue := Random(10);
          TThread.Synchronize(nil,
            procedure
            begin
                  Label1.Text := lValue.ToString;
            end);
      end);
end;

What happens here is that the TTask is used to run some code (starting with {Some calculation that takes time}) in a different thread (that is being determined by the framework behind TTask).

I recommend against using TTask (or any other part of the Delphi Parallel Programming Library) as I agree with Stefan Glienke in [WayBack] Hello, Do you know why the “default” keyword of a class property is sometime defined also as an attribute ? – Paul TOTH – Google+:

If that works as well as the PPL does I would not touch it with a 10 foot pole ;)

With “that”, he refers to the APL (Asynchronous Programming Library [Archive.is]) which got introduced in Delphi XE8 and adds asynchronous support for UI controls, but unlike .NET (which implements it on the .NET TControl equivalent) shifted it down to TComponent probably because that’s the common ancestor for both VCL and FMX. But that’s a topic for another day.

The Delphi Parallel Programming Library (DPL) is a complex and intricate framework originally started as Delphi Parallel Library (DPL) and modelled after [WayBackIntel’s Threading Building Blocks (TBB) and Microsoft’s Task Parallel Library (TPL) (not in WayBack, but moved to the CHM file [WayBack], see also[WayBack] Task Parallel Library changes since the MSDN Magazine article | Parallel Programming with .NET)

Most parts of the DPL were written over at least 7 years time by former Chief Scientist Allen Bauer and introduced in Delphi XE7 as the Delphi Parallel Programming Library (PPL), see [WayBack] Delphi Parallel Programming Library & Memory Managers – Steve Maughan and [WayBack] The Oracle at Delphi: Lock my Object… Please!.

Since Delphi XE7, the PPL hardly got maintenance and now most if not all of the people having knowledge about it have left Embarcadero: early 2016, [Archive.is] Delphi Chief Scientist Allen Bauer Has Left Embarcadero/Idera | Hacker News leaving a big gap as “There are no plans that I’m aware of to move someone into my old position… All those that I would consider qualified are either already gone or are currently looking elsewhere.” (it is not in the [WayBack] part of How safe is Delphis future? Who is the new Lead Compiler Engineer? Who is the new Chief Scientist? – Ralf Stocker – Google+, hence the screen shot).

Luckily, Allen copied most of his old Embarcadero blog over to his personal one (including comments!), so there is quite some historic reference, see for instance [WayBack] Thread pools <> Task handling. – Community Blogs – Embarcadero Community and [WayBack] The Oracle at Delphi: Thread pools <> Task handling.

So back ensuring you can execute some code on the main thread and the questions from the G+ post:

  1. Why is there no easier language construct than wrapping the callback in a procedure (anonymous method).
  2. Why a call to TThread.Synchronize at all?

Lets start with the questions in order I answered them, starting with the my response:

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Posted in Conference Topics, Conferences, Delphi, Development, Event, Software Development | Leave a Comment »

Learn so say ‘No’: ‘No’ your way to trust workshop

Posted by jpluimers on 2019/11/29

[WayBack‘No’ your way to trust workshop slide deck:

Published on 

We should say ‘no’ far more often than we do. Why we don’t, the consequences, and how to get comfortable with and effective in saying ‘no’ is the subject of this workshop. Beauty is that you don’t even need to say ‘no’ in order to express ‘no’. First facilitated at Agile and Beyond 2018.

via: [WayBack] Facilitated my ‘No’ your way to trust workshop today at Agile and Beyond #aab18 Happy that it was well received by the audience of … mostly speakers … – Marjan Venema – Google+

–jeroen

Posted in Conference Topics, Conferences, Event, LifeHacker, Power User | Leave a Comment »

 
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