I tried to run a few of my scripts on a linux machine, and kept getting weird errors like

“: No such file or directory”

I finally figured out that the files were in DOS formatted line separation (\n\r) which was confusing the shell. A quick

dos2unix *.py

fixed things.

I had a very annoying bug in my wxPython application that I couldn’t figure out. In a GUI application that has a status bar and a context menu, any call to self.PopupMenu(mnu) would result in the following:

wx._core.PyAssertionError: C++ assertion “(number>=0) && (number <m_nFields)” failed at ../src/generic/statusbr.cpp(142) in SetStatusText(): invalid status bar field index

I use Boa Constructor to build my wxPython app, and in one of the generated code was the following:

 def _init_ctrls(self, prnt):
        # generated method, don't edit
        wx.Frame.__init__(self, id=wxID_FRAME1, name='', parent=prnt,
              pos=wx.Point(503, 180), size=wx.Size(988, 660),
              style=wx.DEFAULT_FRAME_STYLE, title=u'')
        self._init_utils()
        ...
        self.SetStatusBarPane(3)

setting SetStatusBarPane(-1) disables automatic help text printing to the status bar, but also stops this very annoying bug.

I started programming in python from the days of 1.5.2, and have not kept up to date with some of the new features. Two features that caught me by surprise:

enumerate()  # builtin function

"...".format() # String method

enumerate() takes a list an returns an interator tuple (index,value) as it goes along the sequence. Very handy and obviates the need for the very messy:

for i in range(len(L)):

    print "I need the index {0} and the item {1} at the same time".format(i,L[i])

This illustrates the second new feature I just realized, the .format() method. This apparently replaces the ‘%’ operator and allows formatted strings to include positional replacement strings using {idx} notation.