[Tutor] String Encoding problem
Strax-Haber, Matthew (LARC-D320)
matthew.strax-haber at nasa.gov
Mon Apr 20 23:17:07 CEST 2009
Sorry about that. Hopefully this is better:
In operator:
def __init__(self, path, saveDB=True, cleanUp=True):
'''Constructor'''
## Calculate filesystem paths
self.WORK_DIR = path + '.tmp'
DB_PATH = path + '.xml'
self.SAVE_DB = saveDB ## finish(): Delete unnecessary files created by run?
self.CLEANUP = cleanUp ## finish(): Delete database at end of run?
## Make sure we have a working directory (exception on failed write)
if not os.path.isdir(self.WORK_DIR):
os.mkdir(self.WORK_DIR)
self._db = DB.Database(DB_PATH)
## SOME OTHER ENVIRONMENT SETUP STUFF
def _cleanUpEnvironment(self):
'''Delete temp files created for this run'''
try:
for path,dirs,files in os.walk(self.WORK_DIR, topdown=False):
for f in files: os.unlink(os.path.join(path,f))
for d in dirs: os.rmdir(os.path.join(path,d))
os.rmdir(self.WORK_DIR)
except:
print >>sys.stderr, 'Could not delete temp files; left at:'
print >>sys.stderr, self.WORK_DIR
def finish(self):
'''Clean up and finish the run (write out to the database)'''
if self.SAVE_DB: self._db.commit()
if self.CLEANUP: self._cleanUpEnvironment()
def __del__(self):
## FIXME: Known bug:
## del t at command line works properly
## Ctrl-D, when there is no db file present, results in a LookupError
self.finish()
if __name__ == '__main__':
printHelp()
## Provide tab completion to the user
import readline, rlcompleter
readline.parse_and_bind('tab: complete')
t = OperatorClassName(os.path.splitext(__file__)[0])
In database:
def __init__(self, path):
'''Constructor'''
self.__dbpath = path ## Path to the database
self.load()
def load(self):
'''Read the database out from the file'''
from xml.parsers.expat import ExpatError
if os.path.exists(self.__dbpath):
## Noticed exceptions: IOError, ExpatError
try:
self.root = ET.parse(self.__dbpath).getroot()
except ExpatError:
raise ExpatError('Invalid XML in ' + self.__dbpath)
else:
self.root = ET.Element("root")
def commit(self):
'''Write the database back to the file'''
## Noticed exceptions: IOError
ET.ElementTree(self.root).write(self.__dbpath)
--
~Matthew Strax-Haber
National Aeronautics and Space Administration
Langley Research Center (LaRC)
Co-op, Safety-Critical Avionics Systems Branch
W: 757-864-7378; C: 561-704-0029
Mail Stop 130
Matthew.Strax-Haber at nasa.gov
________________________________
From: Martin Walsh <mwalsh at mwalsh.org>
Date: Mon, 20 Apr 2009 16:05:01 -0500
To: Python Tutor <tutor at python.org>
Cc: "Strax-Haber, Matthew (LARC-D320)" <matthew.strax-haber at nasa.gov>
Subject: Re: [Tutor] String Encoding problem
Forwarding to the list. Matt, perhaps you can repost in plain text, my
mail client seems to have mangled your source ...
Strax-Haber, Matthew (LARC-D320) wrote:
>> *From: *Martin Walsh <mwalsh at mwalsh.org>
>>
>> The environment available to __del__ methods during program termination
>> is wonky, and apparently not very consistent either. I can't say that I
>> completely understand it myself, perhaps someone else can provide a
>> better explanation for both of us, but some of the causes are described
>> in the documentation:
>>
>> http://docs.python.org/reference/datamodel.html#object.__del__
>>
>> What is your rationale for using __del__? Are you trying to force a
>> 'commit()' call on Database instances when your program terminates -- in
>> the case of an unhandled exception, for example?
>
> Perhaps I oversimplified a bit. In my actual code, there is a database
> class and an operator class. The actual structure is this:
>
> In operator:
> def __init__(self, path, saveDB=True, cleanUp=True):
> '''Constructor''' ## Calculate filesystem paths
> self.WORK_DIR = path + '.tmp' DB_PATH = path
> + '.xml' self.SAVE_DB = saveDB ## finish(): Delete
> unnecessary files created by run? self.CLEANUP = cleanUp ##
> finish(): Delete database at end of run? ## Make sure we
> have a working directory (exception on failed write) if not
> os.path.isdir(self.WORK_DIR): os.mkdir(self.WORK_DIR)
>
> self._db = DB.Database(DB_PATH)
> ## SOME OTHER ENVIRONMENT SETUP STUFF
> def _cleanUpEnvironment(self): try: ## Delete
> temp files created for this run for path,dirs,files in
> os.walk(self.WORK_DIR, topdown=False): for f in files:
> os.unlink(os.path.join(path,f)) for d in dirs:
> os.rmdir(os.path.join(path,d)) os.rmdir(self.WORK_DIR)
> except: print >>sys.stderr, 'Could not delete temp
> files; left at:' print >>sys.stderr, self.WORK_DIR def
> finish(self): '''Clean up and finish the run (write out to
> the database)''' if self.SAVE_DB: self._db.commit()
> if self.CLEANUP: self._cleanUpEnvironment()
> def __del__(self): ## FIXME: Known bug: ## del t at
> command line works properly ## Ctrl-D, when there is no db file
> present, results in a LookupError self.finish()
> if __name__ == '__main__':
> printHelp()
> ## Provide tab completion to the user import readline,
> rlcompleter readline.parse_and_bind('tab: complete')
> t = OperatorClassName(os.path.splitext(__file__)[0])
>
> In database:
> def commit(self): '''Write the database back to the file'''
> ## Noticed exceptions: IOError
> ET.ElementTree(self.root).write(self.__dbpath)
>
> The operator also has a series of functions that collect data and enter
> it into the database. Here's the usage pattern I want to have:
>
> User calls Operator.py. User runs a bunch of functions of the form
> t.<someFunc>(<args>). When the user quits, the database will save or not
> save depending on the status of t.SAVE_DB (which some functions in the
> operator will programmatically change).
>
>>
>> HTH,
>> Marty
>>
>>>
>>> Thank you very much. Any and all help or pointers are appreciated.
>>>
>>> ~Matt
>>>
>>> #### db.py ###
>>> from xml.etree import ElementTree as ET
>>> import os
>>>
>>> class Database(object):
>>> def __init__(self, path):
>>> self.__dbpath = path ## Path to the database
>>> self.load()
>>> def __del__(self):
>>> ## FIXME: Known bug:
>>> ## del db at command line works properly
>>> ## Ctrl-D, when there is no db file present, results in a
>>> LookupError
>>> ## and empty xml file
>>> from StringIO import StringIO
>>> from traceback import print_exc
>>> trace = StringIO()
>>> try:
>>> print 5
>>> self.commit()
>>> print 7
>>> except Exception:
>>> print_exc(100, trace)
>>> print trace.getvalue()
>>> def load(self):
>>> if os.path.exists(self.__dbpath):
>>> self.root = ET.parse(self.__dbpath).getroot()
>>> else:
>>> self.root = ET.Element("root")
>>> def commit(self):
>>> ET.ElementTree(self.root).write(self.__dbpath)
>>> db = Database('db.xml')
>>
>> _______________________________________________
>> Tutor maillist - Tutor at python.org
>> http://mail.python.org/mailman/listinfo/tutor
>
> --
> ~Matthew Strax-Haber
> National Aeronautics and Space Administration
> Langley Research Center (LaRC)
> Co-op, Safety-Critical Avionics Systems Branch
> W: 757-864-7378; C: 561-704-0029
> Mail Stop 130
> Matthew.Strax-Haber at nasa.gov
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