🌐 Mailman 3 December 2003 - Python-list - python.org

Python and Tk: Error on Memory Access
by Markus Franke Jan. 2, 2004

Jan. 2, 2004

Hi, i have a problem using Tk with python. Here is a simple script: import Tkinter root=Tkinter.Tk() button=Tkinter.Button(root,text="Click") button.pack() I can see a Window with a Button in it. But the problem now is that every time I enter the Button with the Mouse-Arrow, the Program stops with a "Failure on Memory Access"... in German "Speicherzugriffsverletzung". I have tried several versions of python, Tk and Tkinter but without success. My System: Red Hat 9(Severn), Kernel 2.4.21-20.1.2024.2.1.nptl python 2.2.3 / I tried also version 2.3.2 Tk-8.3.5-88 Tkinter 2.2.3-26 Hope anyone can help me. Thanx, Markus

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PIL: jpeg comment
by Gerrit Holl Jan. 2, 2004

Jan. 2, 2004

Hi, how do I read a JPEG comment with the Python Imaging Library? yours, Gerrit Holl. -- Asperger's Syndrome - a personal approach: http://people.nl.linux.org/~gerrit/english/

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PYTHONPATH unnecessary with PythonWin?
by r.e.s. Jan. 2, 2004

Jan. 2, 2004

I have no PYTHONPATH nor any other python-related environment variables, yet everything seems fine. (I'm using PythonWin with winxp.) As long as modules are loaded through PythonWin, is PYTHONPATH unnecessary? Or am I missing something?

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Test if IDLE is a mature program
by Aubrey Hutchison Jan. 1, 2004

Jan. 1, 2004

### this will test if your version of IDLE on windows is a MATURE program design ### print "Hello world, If Python IDLE is a mature program design it will output this" Save this simple single line program as "select.py" and try to run it. Then exit IDLE and try to restart IDLE. Aubrey

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'inverting' a dict
by Irmen de Jong Jan. 1, 2004

Jan. 1, 2004

Hi I have this dict that maps a name to a sequence of other names. I want to have it reversed, i.e., map the other names each to the key they belong to (yes, the other names are unique and they only occur once). Like this: { "key1": ("value1", "value2"), "key2": ("value3,) } --> { "value1": "key1", "value2": "key1", "value3": "key2" } What I'm doing is using a nested loop: dict2={} for (key,value) in dict1.items(): for name in value: dict2[name] = key which is simple enough, but I'm hearing this little voice in the back of my head saying "there's a simpler solution". Is there? What is it? ;-) Thanks --Irmen.

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canonical file access pattern?
by Hans-Joachim Widmaier Jan. 1, 2004

Jan. 1, 2004

Recently, there was mentioned how someone who had understood Python's error handling would write the "open and read file with error handling" idiom. If I remember correctly, it went like this: try: f = file(filename, op) except IOError, e: # Handle exception else: # Use the file f.close() I don't think that's sufficient. First of all, opening a file is only part of the job--reading and writing can go wrong too, and these are not handled by the above code. Then I've seen OSError as well as IOError raised occassionaly. Seems like I have do this, then: try: f = file(filename, op) except (OSError, IOError), e: # Handle open() error else: try: # read/write to the file f.close() # flushes write buffers, so can fail, too except (OSError, IOError), e: # Handle read/write errors Is it really so wrong, then, to fold the read/write operations and close() into the first try suite and handle all those errors in one go? I'd just like to have a definitive pattern that I can stick to that is considered bullet-proof. Hans-Joachim Widmaier

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Re: selecting a random item from a set
by Alexander Schmolck Jan. 1, 2004

Jan. 1, 2004

Jp Calderone <exarkun(a)intarweb.us> writes: > > > Alexander Schmolck wrote: > > Maybe not insensibly -- the fairly generic approach outlined above that will > > work for any iterable with len is clearly not desirable as default (because of > > its time complexity), and just using it as a fallback won't work either, > > because AFACT there is no way for `choice` to find out whether its argument is > > a sequence or not. > > > def choice(self, seq): > """Choose a random element from a non-empty sequence.""" > try: > return seq[int(self.random() * len(seq))] > except TypeError: > # Fallback algorithm choice(dict(1:"gets this", 2:"gets that", "three":"gets the key")) 'as

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fatal error: GC object already tracked
by Vikram Jan. 1, 2004

Jan. 1, 2004

hi, i have a program which uses multiple threads and downloads pages using pycurl and processes these pages among other things. the program works fine with python 2.2 and pycurl 7.10.8 ; with python 2.3 i get two kinds of errors maybe related? a) python dumps core and prints out "Fatal Python error: GC object already tracked" b) the program just waits at update_refs() function inside the python GC code path and doesn't append anything to the logs nor perform any activity. any idea why or suggestions ? Vikram ps: the Fatal Python error: GC object already tracked" error seems to be an open bug filed by someone else in october 2003. --- (gdb) bt #0 0x8819082c in kill () from /usr/lib/libc_r.so.4 #1 0x881dea8a in abort () from /usr/lib/libc_r.so.4 #2 0x80d4eb5 in Py_FatalError () #3 0x80855b4 in PyTuple_New () #4 0x80b340a in load_args () #5 0x80b2dc8 in call_function () #6 0x80b02ac in eval_frame () #7 0x80b3054 in fast_function () #8 0x80b2eb5 in call_function () #9 0x80b02ac in eval_frame () #10 0x80b3054 in fast_function () #11 0x80b2eb5 in call_function () #12 0x80b02ac in eval_frame () #13 0x80b3054 in fast_function () #14 0x80b2eb5 in call_function () #15 0x80b02ac in eval_frame () #16 0x80b1821 in PyEval_EvalCodeEx () #17 0x80b30fd in fast_function () #18 0x80b2eb5 in call_function () #19 0x80b02ac in eval_frame () #20 0x80b1821 in PyEval_EvalCodeEx () #21 0x80b30fd in fast_function () #22 0x80b2eb5 in call_function () #23 0x80b02ac in eval_frame () #24 0x80b1821 in PyEval_EvalCodeEx () #25 0x80f6fc6 in function_call () #26 0x805ad0f in PyObject_Call () #27 0x80b3750 in ext_do_call () #28 0x80b03d1 in eval_frame () #29 0x80b3054 in fast_function () #30 0x80b2eb5 in call_function () #31 0x80b02ac in eval_frame () #32 0x80b1821 in PyEval_EvalCodeEx () #33 0x80f6fc6 in function_call () #34 0x805ad0f in PyObject_Call () #35 0x8061b7d in instancemethod_call () #36 0x805ad0f in PyObject_Call () #37 0x80b2a80 in PyEval_CallObjectWithKeywords () #38 0x80db217 in t_bootstrap () #39 0x8816b0a8 in _thread_start () from /usr/lib/libc_r.so.4 #40 0x0 in ?? ()

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Maybe a stupid idea
by sebb＠linuxcult.com Jan. 1, 2004

Jan. 1, 2004

I'm kind of newbie to programming, but I thought of something and I want some opinions on that. It's about a new instruction block to do some cycles. I thought about that because it's not very easy to program a cycle. Here is a simple example : b=0 while b < 50: b+=1 print "*" * b while b > 0: b-= 1 print "*" * b It takes two while blocks to do a cycle. I know that cycles is not a structure of any programming language, but I want some opinions the know if my idea is stupid or not. If the idea is not so stupid, python may be the first language to have a completely new structure block :-) Note : English is not my mother tongue so the message can have mistakes.

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Uplevel functionality
by Maciej Sobczak Jan. 1, 2004

Jan. 1, 2004

Hello, I would like to know if there is any possibility in Python to execute arbitrary scripts in the context higher in the stack frame. In essence, I would like to have the equivalent of the following Tcl code: proc repeat {n script} { for {set i 0} {$i < $n} {incr i} { uplevel $script } } This allows me to do: repeat 5 {puts "hello"} prints: hello hello hello hello hello Or this: set i 10 repeat 5 {incr i} puts $i prints: 15 That second example shows that the script provided as a second parameter to the "repeat" procedure (the script is "incr i") is executed in the context where the procedure was called, not locally in the procedure itself. The strongest analogy to the above repeat procedure in Tcl would be a hypothetical Python function: def repeat(n, script): for i in xrange(n): EVALUATE script HIGHER IN THE STACK #??? Thank you very much, -- Maciej Sobczak : http://www.msobczak.com/ Programming : http://www.msobczak.com/prog/

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