Iterate through dictionary of file objects and file names

[Julian Yap]

Hi all,
I'm trying to get some ideas on the best way to do this.
In this particular coding snippet, I was thinking of creating a 
dictionary of file objects and file names.  These would be optional 
files that I could open and parse.  At the end, I would easily close off 
the files by iterating through the dictionary.

---< CODE FOLLOWS >---
optionalfiles = {fileAreaCode: "areacode.11", fileBuild: "build.11"}
# Try to see if optional file exists, if so, open.
try:
for key, optionalFile in optionalFiles.iteritems():
key = open(optionalFile, "r")
except IOError:
key = False
...
# Close optionally open files
for key, optionalFile in optionalFiles.iteritems():
if optionalFile:
print "Closing: %s" % optionalFile
key.close()
---< END CODE >---
My questions are:
Is this even possible in a dictionary to have a key of a file object?
If so, how do I initialise an empty file object?  I mean, something 
along the lines of:
fileAreaCode = open("", "r")
If not, any suggestions on achieving openning optional files in a loop? 
 Otherwise I'm stuck with:

---< BEGIN >---
# Optional input files
try:
fileAreaCode = open("areacode.11", "r")
except:
fileAreaCode = False
try:
fileBuild = open("build.11", "r")
except:
fileBuild = False
...
# Close files
for optionalFile in [fileAreaCode, fileBuild]:
if optionalFile:
print "Closing: %s" % str(optionalFile)
optionalFile.close()
---< END >---
Thanks,
Julian
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Re: Iterate through dictionary of file objects and file names

[Julian Yap]

Brian Beck wrote:
File objects as keys sounds pretty dangerous. I'm curious why the first 
thought that popped into your head wasn't using the file NAMES as keys 
instead? Here's my go at it. (Is Google Groups nice to indentation using 
spaces? I can't remember.)

optionalFiles = dict.fromkeys(['areacode.11', 'build.11'], None)
# To open optionalFiles...
for fileName in optionalFiles:
try:
optionalFiles[fileName] = open(fileName, "r")
print "Opened: %s" % fileName
except IOError:
# Values are already initialized to None.
print "File not found: %s" % fileName
# To close optionalFiles...
for fileName, fileObject in optionalFiles.iteritems():
if fileObject:
fileObject.close()
print "Closed: %s" % fileName
# Rebinding fileObject here won't modify the dictionary,
# so access it through the key.
optionalFiles[fileName] = None
Brain,
Thanks for your help.  I never thought of it like that.
I guess in my original thinking, in the processing of the optional files 
I would start off each code block with something like:

if fileAreaCode:
...
But now I can just do:
if optionalFiles['areacode.11']:
...
I think I was just too much in the above mindset to think clearly about 
the dictionary.

Using a file object as a key!?  What was I thinking :P
Julian
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