Develop Reference

max_iters doesn't seem to work with GLPK_MI solver in Python

I'm debugging my code right now and since it's running with some datas and not with other ones, I wanted to set the 'max_iters' option to 1 to see if it works in only 1 iteration or if it needs more. I realised it doesn't seem to even use it. I tried putting a string "hello" instead of an int and it even worked. Do someone knows if it's a known problem?
self.prob.solve(solver="GLPK_MI", max_iters=1)
I'm using the CVXPY module with CVXOPT.
EDIT:
I want to do this because I don't get an error, it just continues to run forever. And with the project I'm working on it can take a lot of time to run so I wonder if it's really not working or if it's just a question of time.

Wouldn't be better if you set the max iterations as a variable? (just a suggestion)
In any case, in CVXOPT you need to set the max number of iteration as
'maxiters' : 1
or you can set it as a variable and then call solver as per below
opts = {'maxiters' : 1}
self.prob.solve(solver="GLPK_MI", options = opts)

Delphi 4 Python

I want to use the Delphi 4 Python components from here https://github.com/pyscripter/python4delphi
but I don't want to drop the components on a form, I want everything in code , my code goes like this :
var
PythonEngine_netA: TPythonEngine;
PythonInputOutput_netA: TPythonInputOutput;
begin
PythonEngine_netA := TPythonEngine.Create(Self);
PythonInputOutput_netA := TPythonInputOutput.Create(Self);
try
/// configure the components
PythonEngine_netA.DllName:='python39.dll';
PythonEngine_netA.IO := PythonInputOutput_netA;
PythonEngine_netA.UseLastKnownVersion := True;
PythonInputOutput_netA.OnSendUniData := PythonInputOutput_SendUniData;
PythonInputOutput_netA.UnicodeIO := True;
PythonInputOutput_netA.RawOutput := True;
/// execute the script
PythonEngine_netA.ExecString(UTF8Encode(mmo_pythoncode.text));
finally
PythonEngine_netA.free;
PythonInputOutput_netA.free;
end;
execution of this code fails, error msg : "Python is not properly initialized",
what did I miss to use this code ?

One quick look at PythonEngine.pas (or even better: always search all files for the error message to find out where and why an error is returned) tells me you missed calling PythonEngine_netA.Initialize().
Also note that /Demos describes:
Demo34 Dynamically creating, destroying and recreating PythonEngine. Uses PythonVersions
So please have a look at /Demos/Demo34/Unit1.pas how it is done there with (almost) no components. Or run the whole project in general, preferably in debug mode single stepping thru it be aware which method does what.

You just forgot to load the Dll:
PythonEngine_netA.UseLastKnownVersion:= True;
//PythonEngine_netA.opendll(PYDLL)
PythonEngine_netA.LoadDll;
PythonEngine_netA.IO:= PythonInputOutput_netA;

SWIG c to python lost function?

considering:
https://github.com/dmichel76/ViSi-Genie-RaspPi-Library
I've tried a serial read and a write, from raspbian to 4d panel, and it all worked fine.
I 'm trying to use a slider controller, this way it work for one minute then goes down returning -1 at read.
import geniePi as D
import wiringpi2 as W
W.wiringPiSetup()
D.genieSetup("/dev/ttyAMA0", 115200)
while 1:
a = D.genieReadObj(32,0)
print ("a:" % (a))
I'm looking at genieGetReply to solve this issue(to avoid the use of ReadObj):
But looking at swig files seems like genieReplyAvail is always considered as 0, am I right?
SWIGINTERN PyObject *_wrap_genieReplyAvail(PyObject *SWIGUNUSEDPARM(self), PyObject *args) {
PyObject *resultobj = 0;
int result;
So genieGetReply() isn't called.
It appear that to use genieGetReply() I must create a class of the struct genieReplyStruct.
x =D.genieReplyStruct()
D.genieGetReply(x)
(if geniReplyAvail never get other value than 0 so this stay forever in the delay(1) statement)
I cannot understand how this should be implemented and called, so I kindly ask you a little advice.

I experienced exactly the same issue. I fixed it as follow:
Did you check that you report a message from the Workshop software ?
Select the button, go to the Events tab, and put "report Message" in "On Changed".
Build/download and try again. It should work now.
Hope it helps.

What does windows error 0 "ERROR_SUCCESS" mean?

I've written a python program which read a stdout of another process by the pipe redirection.
However, the program sucks in this line:
print "[Input Thread] ", self.inputPipe.readline(ii)
The error is IOError: [Errno 0] Error
I found the explanation of windows errno 0. It makes confused because it defined as:
The operation completed successfully.
Why does an operation completed successfully lead to an error?

The name can trick you but ERROR_SUCCESS actually means there was no error.
From https://msdn.microsoft.com/en-us/library/windows/desktop/ms681382.aspx:
ERROR_SUCCESS
0 (0x0)
The operation completed successfully.

I know this is kind of old but having spent a fair amount of time trying to find a complete answer without success. So I figured I'd share what I've figured out.
The complete answer of how this happens, is when the pInvoke method you called "fails" but not because of an error.
huh you think
For example lets say you need to unhook a windows hook, but it gets called twice due to a bit of spaghetti or a paranoid level of defensive programming in your object architecture.
// hook assigned earlier
// now we call our clean up code
if (NativeMethods.UnhookWindowsHookEx(HookHandle) == 0)
{
// method succeeds normally so we do not get here
Log.ReportWin32Error("Error removing hook", Marshal.GetLastWin32Error());
}
// other code runs, but the hook is never reattached,
// due to paranoid defensive program you call your clean up code twice
if (NativeMethods.UnhookWindowsHookEx(HookHandle) == 0)
{
// pInvoke method failed (return zero) because there was no hook to remove
// however there was no error, the hook was already gone thus ERROR_SUCCESS (0)
// is our last error
Log.ReportWin32Error("Error removing hook", Marshal.GetLastWin32Error());
}

The windows API can be tricky. Most likely, the error number was not properly retrieved by the second program you mentioned. It was either overwritten or not pulled in at all; so it defaulted to 0.
You didn't say what the other program was; but for example, in .net, it is easy to omit the 'SetLastError' flag when declaring your external calls.
[DllImport('kernel32.dll', SetLastError = true)]
https://www.medo64.com/2013/03/error-the-operation-completed-successfully/

Updating python variable from c

I am having an intermittent error causing my Python module to crash, and I'm assuming it's because of a memory error occurring by not getting the refcounts correct in the c code. I have a bit of code that gets a response at a random time from a remote location. Based on the data received, it needs to update a data variable which I should have access to in Python. What's the best way to accomplish this? The following code runs most of the time, and it works correctly when it does, but when it doesn't it crashes Python (bringing up the visual studio debug box). Thanks.
if (event == kResponseEvent) {
list = PyList_New(0);
for (i = 0; i < event->count; i++) {
PyList_Append(list, Py_BuildValue("{s:i, s:s}",
"id", event->id,
"name", event->name));
}
PyModule_AddObject(module, "names", list);
}

PyModule_AddObject() steals a reference. As such, you should not be decrefing list after.

PyList_New() can return NULL to indicate an error, which you aren't checking for. Py_BuildValue() can return NULL to indicate an error, which you aren't checking for. PyList_Append() can return -1 to indicate an error, which you're also not checking for. PyList_Append() doesn't steal the reference, so you're leaking the reference to the dict returned by Py_BuildValue(). The latter may be causing you to run out of memory, which can cause Py_BuildValue() or PyList_Append() to fail, and your failure to handle the error can cause a crash.
(Something else can also cause Py_BuildValue() or PyList_Append() to fail, but that's hard to guess at from just this snippet.)