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Groups > comp.lang.python > #31164 > unrolled thread
| Started by | Wanderer <wanderer@dialup4less.com> |
|---|---|
| First post | 2012-10-12 08:36 -0700 |
| Last post | 2012-10-13 06:40 -0700 |
| Articles | 9 — 5 participants |
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Checking for dlls in ctypes Wanderer <wanderer@dialup4less.com> - 2012-10-12 08:36 -0700
Re: Checking for dlls in ctypes Dave Angel <d@davea.name> - 2012-10-12 12:28 -0400
Re: Checking for dlls in ctypes Wanderer <wanderer@dialup4less.com> - 2012-10-12 10:57 -0700
Re: Checking for dlls in ctypes Wanderer <wanderer@dialup4less.com> - 2012-10-12 10:57 -0700
Re: Checking for dlls in ctypes Nobody <nobody@nowhere.com> - 2012-10-13 12:32 +0100
Re: Checking for dlls in ctypes MRAB <python@mrabarnett.plus.com> - 2012-10-12 17:57 +0100
Re: Checking for dlls in ctypes Wanderer <wanderer@dialup4less.com> - 2012-10-12 10:52 -0700
Re: Checking for dlls in ctypes Wanderer <wanderer@dialup4less.com> - 2012-10-12 10:52 -0700
Re: Checking for dlls in ctypes 88888 Dihedral <dihedral88888@googlemail.com> - 2012-10-13 06:40 -0700
| From | Wanderer <wanderer@dialup4less.com> |
|---|---|
| Date | 2012-10-12 08:36 -0700 |
| Subject | Checking for dlls in ctypes |
| Message-ID | <975da919-c70a-492a-9d49-62254a76eb6c@googlegroups.com> |
I'm trying to write some code that will load one of three dll depending on the one available. I've tried the code below, but it doesn't work. The try except doesn't catch the exception. Is there a way to do this?
try:
self.dll = windll.pvcam64
except:
print "No pvcam64"
try:
self.dll = windll.pvcam32
except:
print "No pvcam32"
try:
self.dll = windll.pvcam
except:
print "No pvcam"
return
else:
print "installed pvcam"
else:
print "installed pvcam32"
else:
print "installed pvcam64"
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| From | Dave Angel <d@davea.name> |
|---|---|
| Date | 2012-10-12 12:28 -0400 |
| Message-ID | <mailman.2092.1350059331.27098.python-list@python.org> |
| In reply to | #31164 |
On 10/12/2012 11:36 AM, Wanderer wrote: > I'm trying to write some code that will load one of three dll depending on the one available. I've tried the code below, but it doesn't work. The try except doesn't catch the exception. Is there a way to do this? > > try: > self.dll = windll.pvcam64 > except: > print "No pvcam64" > try: > self.dll = windll.pvcam32 > except: > print "No pvcam32" > try: > self.dll = windll.pvcam > except: > print "No pvcam" > return > else: > print "installed pvcam" > else: > print "installed pvcam32" > else: > print "installed pvcam64" > I can't help you find the dll's, because I don't run Windows. But I could help you write a clearer question: "doesn't work" is thoroughly useless for describing errors. If you're getting an exception, show us the full traceback. That will show which statement got the exception that wasn't caught. Next question is which of the dlls is missing. Are you getting an exception because it's missing or because of something more fundamental, like nesting exception handlers? Using bare excepts is almost never a good idea. If it "works" you get no clues what went wrong. For example, a typo in source code can trigger a bare exception, as can a user typing Ctrl-C. So when you're using bare excepts, you have robbed the user of any way to terminate the program. If I were you, I'd be writing a loop so there's only one try block. Too much duplicated code in the way you're doing it. -- DaveA
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| From | Wanderer <wanderer@dialup4less.com> |
|---|---|
| Date | 2012-10-12 10:57 -0700 |
| Message-ID | <f8610ca5-d92d-4755-96b1-4abd79de6a0f@googlegroups.com> |
| In reply to | #31166 |
On Friday, October 12, 2012 12:29:02 PM UTC-4, Dave Angel wrote: > On 10/12/2012 11:36 AM, Wanderer wrote: > > > I'm trying to write some code that will load one of three dll depending on the one available. I've tried the code below, but it doesn't work. The try except doesn't catch the exception. Is there a way to do this? > > > > > > try: > > > self.dll = windll.pvcam64 > > > except: > > > print "No pvcam64" > > > try: > > > self.dll = windll.pvcam32 > > > except: > > > print "No pvcam32" > > > try: > > > self.dll = windll.pvcam > > > except: > > > print "No pvcam" > > > return > > > else: > > > print "installed pvcam" > > > else: > > > print "installed pvcam32" > > > else: > > > print "installed pvcam64" > > > > > > > I can't help you find the dll's, because I don't run Windows. But I > > could help you write a clearer question: > > > > "doesn't work" is thoroughly useless for describing errors. If you're > > getting an exception, show us the full traceback. That will show which > > statement got the exception that wasn't caught. Next question is which > > of the dlls is missing. Are you getting an exception because it's > > missing or because of something more fundamental, like nesting exception > > handlers? > > > > Using bare excepts is almost never a good idea. If it "works" you get > > no clues what went wrong. For example, a typo in source code can > > trigger a bare exception, as can a user typing Ctrl-C. So when you're > > using bare excepts, you have robbed the user of any way to terminate the > > program. > > > > If I were you, I'd be writing a loop so there's only one try block. Too > > much duplicated code in the way you're doing it. > > > > > > > > -- > > > > DaveA Sorry. It was a WindowsError, but the code I posted now works for me and I can't reproduce the problem. I'll be more diligent in the future.
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| From | Wanderer <wanderer@dialup4less.com> |
|---|---|
| Date | 2012-10-12 10:57 -0700 |
| Message-ID | <mailman.2098.1350064633.27098.python-list@python.org> |
| In reply to | #31166 |
On Friday, October 12, 2012 12:29:02 PM UTC-4, Dave Angel wrote: > On 10/12/2012 11:36 AM, Wanderer wrote: > > > I'm trying to write some code that will load one of three dll depending on the one available. I've tried the code below, but it doesn't work. The try except doesn't catch the exception. Is there a way to do this? > > > > > > try: > > > self.dll = windll.pvcam64 > > > except: > > > print "No pvcam64" > > > try: > > > self.dll = windll.pvcam32 > > > except: > > > print "No pvcam32" > > > try: > > > self.dll = windll.pvcam > > > except: > > > print "No pvcam" > > > return > > > else: > > > print "installed pvcam" > > > else: > > > print "installed pvcam32" > > > else: > > > print "installed pvcam64" > > > > > > > I can't help you find the dll's, because I don't run Windows. But I > > could help you write a clearer question: > > > > "doesn't work" is thoroughly useless for describing errors. If you're > > getting an exception, show us the full traceback. That will show which > > statement got the exception that wasn't caught. Next question is which > > of the dlls is missing. Are you getting an exception because it's > > missing or because of something more fundamental, like nesting exception > > handlers? > > > > Using bare excepts is almost never a good idea. If it "works" you get > > no clues what went wrong. For example, a typo in source code can > > trigger a bare exception, as can a user typing Ctrl-C. So when you're > > using bare excepts, you have robbed the user of any way to terminate the > > program. > > > > If I were you, I'd be writing a loop so there's only one try block. Too > > much duplicated code in the way you're doing it. > > > > > > > > -- > > > > DaveA Sorry. It was a WindowsError, but the code I posted now works for me and I can't reproduce the problem. I'll be more diligent in the future.
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| From | Nobody <nobody@nowhere.com> |
|---|---|
| Date | 2012-10-13 12:32 +0100 |
| Message-ID | <pan.2012.10.13.11.32.15.146000@nowhere.com> |
| In reply to | #31166 |
On Fri, 12 Oct 2012 12:28:17 -0400, Dave Angel wrote: > Using bare excepts is almost never a good idea. If it "works" you get no > clues what went wrong. For example, a typo in source code can trigger a > bare exception, as can a user typing Ctrl-C. So when you're using bare > excepts, you have robbed the user of any way to terminate the program. If you want to catch any error, use "except StandardError:". That covers all errors but not things like KeyboardInterrupt (Ctrl-C) or SystemExit (sys.exit()). In situations such as this, where you try multiple candidates until one succeeds, there's no reason to be any more specific than that. In any case, Python's lack of formal interfaces makes it hard to reliably be more specific. However: you should bear in mind that loading the wrong DLL may just result in an OS-level exception (e.g. segfault), which can't be caught. It's preferable to allow the DLL to be explicitly selected e.g. in a configuration file.
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| From | MRAB <python@mrabarnett.plus.com> |
|---|---|
| Date | 2012-10-12 17:57 +0100 |
| Message-ID | <mailman.2094.1350061025.27098.python-list@python.org> |
| In reply to | #31164 |
On 2012-10-12 16:36, Wanderer wrote:
> I'm trying to write some code that will load one of three dll depending on the one available. I've tried the code below, but it doesn't work. The try except doesn't catch the exception. Is there a way to do this?
>
> try:
> self.dll = windll.pvcam64
> except:
> print "No pvcam64"
> try:
> self.dll = windll.pvcam32
> except:
> print "No pvcam32"
> try:
> self.dll = windll.pvcam
> except:
> print "No pvcam"
> return
> else:
> print "installed pvcam"
> else:
> print "installed pvcam32"
> else:
> print "installed pvcam64"
>
This works for me:
for name in ("pvcam64", "pvcam32", "pvcam"):
try:
self.dll = getattr(windll, name)
except OSError:
print "No " + name
else:
print "Installed " + name
return
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| From | Wanderer <wanderer@dialup4less.com> |
|---|---|
| Date | 2012-10-12 10:52 -0700 |
| Message-ID | <cd188643-162a-483f-bb68-6ea48c50a503@googlegroups.com> |
| In reply to | #31168 |
On Friday, October 12, 2012 12:57:06 PM UTC-4, MRAB wrote:
> On 2012-10-12 16:36, Wanderer wrote:
>
> > I'm trying to write some code that will load one of three dll depending on the one available. I've tried the code below, but it doesn't work. The try except doesn't catch the exception. Is there a way to do this?
>
> >
>
> > try:
>
> > self.dll = windll.pvcam64
>
> > except:
>
> > print "No pvcam64"
>
> > try:
>
> > self.dll = windll.pvcam32
>
> > except:
>
> > print "No pvcam32"
>
> > try:
>
> > self.dll = windll.pvcam
>
> > except:
>
> > print "No pvcam"
>
> > return
>
> > else:
>
> > print "installed pvcam"
>
> > else:
>
> > print "installed pvcam32"
>
> > else:
>
> > print "installed pvcam64"
>
> >
>
> This works for me:
>
>
>
> for name in ("pvcam64", "pvcam32", "pvcam"):
>
> try:
>
> self.dll = getattr(windll, name)
>
> except OSError:
>
> print "No " + name
>
> else:
>
> print "Installed " + name
>
> return
Yes that works for me, too. Thanks
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| From | Wanderer <wanderer@dialup4less.com> |
|---|---|
| Date | 2012-10-12 10:52 -0700 |
| Message-ID | <mailman.2097.1350064361.27098.python-list@python.org> |
| In reply to | #31168 |
On Friday, October 12, 2012 12:57:06 PM UTC-4, MRAB wrote:
> On 2012-10-12 16:36, Wanderer wrote:
>
> > I'm trying to write some code that will load one of three dll depending on the one available. I've tried the code below, but it doesn't work. The try except doesn't catch the exception. Is there a way to do this?
>
> >
>
> > try:
>
> > self.dll = windll.pvcam64
>
> > except:
>
> > print "No pvcam64"
>
> > try:
>
> > self.dll = windll.pvcam32
>
> > except:
>
> > print "No pvcam32"
>
> > try:
>
> > self.dll = windll.pvcam
>
> > except:
>
> > print "No pvcam"
>
> > return
>
> > else:
>
> > print "installed pvcam"
>
> > else:
>
> > print "installed pvcam32"
>
> > else:
>
> > print "installed pvcam64"
>
> >
>
> This works for me:
>
>
>
> for name in ("pvcam64", "pvcam32", "pvcam"):
>
> try:
>
> self.dll = getattr(windll, name)
>
> except OSError:
>
> print "No " + name
>
> else:
>
> print "Installed " + name
>
> return
Yes that works for me, too. Thanks
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| From | 88888 Dihedral <dihedral88888@googlemail.com> |
|---|---|
| Date | 2012-10-13 06:40 -0700 |
| Message-ID | <f50647a5-0117-4e82-aaab-1792d838ed2b@googlegroups.com> |
| In reply to | #31164 |
Wanderer於 2012年10月12日星期五UTC+8下午11時36分27秒寫道： > I'm trying to write some code that will load one of three dll depending on the one available. I've tried the code below, but it doesn't work. The try except doesn't catch the exception. Is there a way to do this? > > > > try: > > self.dll = windll.pvcam64 > > except: > > print "No pvcam64" > > try: > > self.dll = windll.pvcam32 > > except: > > print "No pvcam32" > > try: > > self.dll = windll.pvcam > > except: > > print "No pvcam" > > return > > else: > > print "installed pvcam" > > else: > > print "installed pvcam32" > > else: > > print "installed pvcam64" In linux there are shared libraries that could be linked in the runtime. But for the security concerns this requres the system administrator account to install shared libraries.
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