Develop Reference

python os.system("chcp 65001") does not work

Windows cmd does not handle utf8 well when executing print statements in python.
Many people said that we can type in "chcp 65001" before executing the python script in the cmd.
In our situation, we want to implement an app (in python pyc) with a desktop icon in Windows.
Thus our first solution is adding os.system("chcp 65001") to the source python script before the main function.
But somehow this did not work. Then some people said trying os.system("/k chcp 65001").
But this did not work either.
Our second soluiton is using a bat file with two lines, the first line is "chcp 65001" while the second is "python my.pyc" where my.pyc is main program of our app.
But this solution seems inconsistent since in some environment it failed while in others, it did not fail.
Moreover, with this solution, Windows does not allow us to change the logo (or icon image) of bat file.
Can someone help us solve this problem with cmd and utf8 with python scripts?

Tkinter program compiled with pyinstaller crash on launch

I'm asking help today because I'm new to Tkinter and Pyinstaller (and python in general) and I'm having troubles with it.
I have a simple app working with sqlite, tkinter and pyinstaller to compile all of this in an executable program, the entrance point of my program is a file named main.py
This file calls all the dependancies (like the sqlite module for python, tkinter and my other files like classes etc...)
I made a very simple interface, with a Hello World in a tkinter label and a button to go to page 2 which displays page2 (also in a label), just to see if I'm capable of making it all run and compile all of these pieces together.
I can run it throught my shell executing it like : python main.py and everything is working fine.
But when I run pyinstaller on my linux machine, and start executing the program, nothing appears, my database.db (sqlite database file) is created but I don't have any interface like when I run it with my shell. The thing is getting even worse on windows where, once I've my .exe it just opens a shell and crash after few seconds, not even creating the database.
What I did is I created a 'log file', in which I write the steps of the program.
As you can see on the following picture, the 2 first prints are wrote in my log file (on linux), so I think it crashes when I try to create the window.
If any of you have an idea on what I do wrong, I would really appreciate help :)

General
From the PyInstaller manual:
Before you attempt to bundle to one file, make sure your app works correctly when bundled to one folder. It is is much easier to diagnose problems in one-folder mode.
As the comments suggested, use a catch-all try/except block to log all exceptions to a file. That is probably the best way to see what is really happening. Make sure that the logfile is created in an existing location where you have the necessary permissions.
I would suggest to take advantage of the built-in logging module instead of creating your own. It can e.g. automatically add from which file a log line was created.
IMHO, it is probable that the failures on Linux and ms-windows have completely different causes. You should probably treat them as different issues.
Linux
When you use single file mode, that file is unpacked into a temporary folder, probably somewhere in /tmp. Some Linux distributions mount the /tmp filesystem with the noexec flag. This is incompatible with PyInstaller.
ms-windows
On windows, there are basically two different Pythons; python.exe and pythonw.exe. Basically it is one of the quirks of windows that this is necessary. The latter is for GUI programs like tkinter programs. A tkinter script should not show a cmd window. So I'm guessing that PyInstaller calls your command with python.exe instead of pythonw.exe. From the manual:
By default the bootloader creates a command-line console (a terminal window in GNU/Linux and Mac OS, a command window in Windows). It gives this window to the Python interpreter for its standard input and output. Your script’s use of print and input() are directed here. Error messages from Python and default logging output also appear in the console window.
An option for Windows and Mac OS is to tell PyInstaller to not provide a console window. The bootloader starts Python with no target for standard output or input. Do this when your script has a graphical interface for user input and can properly report its own diagnostics.
As noted in the CPython tutorial Appendix, for Windows a file extention of .pyw suppresses the console window that normally appears. Likewise, a console window will not be provided when using a myscript.pyw script with PyInstaller.
Also, on windows it can matter which Python distribution you're using. I used to be a fan of Anaconda, but lately I've come to prefer the python.org version because it gives me less headaches. On anaconda Python I had the problem that tkinter programs would not launch without showing a cmd window, whatever I tried. Only switching to python.org Python solved that problem.

How to know if I'm running a python script from eclipse

I have a python script which is sometimes invoked from command line and sometimes from eclipse (during SW build).
Is there a way to know from within the python script if it is invoked from eclipse (without sending the script command line arguments)?
Thanks.

I don't use Eclipse anymore since PyCharm is much more efficient for Python programming, but here are some ideas you can try:
⬥ You may have (or you can set) an environment variable when the script is launched with Eclipse.
For instance, with PyCharm, we have:
import os
print("PYCHARM_HOSTED: {!r}".format(os.environ['PYCHARM_HOSTED']))
# -> PYCHARM_HOSTED: '1'
You can have a similar environment variable with Eclipse. Check the os.environ dictionary.
⬥ You can have a different virtualenv, check the sys.executable value:
import sys
print(sys.executable)
# -> /Users/laurentlaporte/virtualenv/my_app/bin/python
⬥ When Eclipse launch your Python application, it creates a child process. In your Python application, you can search the parent process. It is a little complex, so…
To do that, you need to use PsUtil.

py-appscript is starting a new Finder instance

i have a py2app application, which runs an appscript using py-appscript. the Applescript code is this one line:
app('Finder').update(<file alias of a certain file>)
What this normally does is update a file's preview in Finder. It works most of the time, except for Leopard. In Leopard, everytime that script is executed, instead of updating the file, it starts a new instance of Finder. What am I doing wrong? The app was built on the same machine (the Leopard).

Seeing as how py-appscript is a layer between python and the application you are scripting via Applescript, I would suggest porting the statement to pure Applescript and see if it works there. There are a lot of things that can go wrong with Applescript (and your statement alone) to begin with and it's not obvious what is the expected before with py-appscript when an error occurs.

How to properly use PyDev with two different Python versions with scripts that are recalling other python scripts?

The story began with a very strange error while I was running my script from PyDev. Running the same script from outside will not encounter the same problem.
Fatal Python error: Py_Initialize: can't initialize sys standard streams
File "C:\Python26\lib\encodings\__init__.py", line 123
raise CodecRegistryError,\
^
SyntaxError: invalid syntax
This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.
I was able to find why this is happening: In PyDev I use two different Python versions: 3.1 that is the default installation and 2.6 as the alternative one.
My Windows Environment does not contains PYTHONHOME, CLASSPATH, PYTHONPATH but PyDev does add them.
Now the problem is at one stage my python script does execute another python script using os.system(python second.py) and the second script will fail with the above error.
Now I'm looking to find a way to prevent this issue, issue that is happening because it will run the execute the default python using the settings for the non-default one (added by PyDev).
I do not want to change the standard call (python file.py) but I want to be able to run my script from pydev without problem and being able to use default or alternative python environment.
Any ideas?

I found a solution that seams acceptable specially because it will not interfere with running the scripts on other systems, just to run python -E second.py - this will force Python to ignore PYTHON* environment variables.

I may not be understanding this quite right, but I think you're invoking a script from pydev that works okay, but this script executes another script which requires a different version.
While this would unfortunately be installation-specific, you could use os.system("c:\absolute\path\to\proper\version\of\python.exe second.py").
If PyDev is setting up conflicting environmental variables, you may want to look into subprocess over os.system.
http://docs.python.org/library/subprocess.html#using-the-subprocess-module
This will allow you to invoke a process with a handle, so you can optionally wait for it to terminate. It will also allow you to pass environment variables upon execution.

I believe your call should be:
import sys
os.system(sys.executable+ ' second.py')
So that you guarantee you're using the same interpreter you're currently running and not launching the other one (or did you really mean to use the other interpreter?)