create class instance and append to list

Question

I'm low on the Python learning curve and I think missing something basic regarding class instantiation. In my code below, I have a simple class that contains formats for files and directories I want to save in a list during a recursive search. Filenames are save separately from directory names in the class and I have two instances. In one, I'm looking for files and directories with the text "RFI" in them, and the other I'm looking for "CCO". After running, the print statement shows all of the matches in both instances, rather than the RFI matches in the RFI instance and the CCO matches in the CCO instance. It's like "fileMatches" and "dirMatches" are behaving as static variables (if I'm getting my terminology correctly), so appending to one instance's list appends to both?

import fnmatch
import os

path = '.'
allDocs = []

class Docs :
    title = []
    nameFormats = []
    fileMatches = []
    dirMatches = []
    def __init__ (self, inTitle, inFormats):
        self.title = inTitle
        self.nameFormats = inFormats

allDocs.append(Docs('RFI','RFI*[0-999]*'))
allDocs.append(Docs('CCO','CCO*[0-999]*'))

for root, dirnames, filenames in os.walk(path):
    print ("Root: " + root)
    for currDoc in allDocs :
        for currDirname in fnmatch.filter(dirnames, currDoc.nameFormats):
            currDoc.dirMatches.append(currDirname)
        for currFilename in fnmatch.filter(filenames, currDoc.nameFormats):
            currDoc.fileMatches.append(currFilename)

print ("------- Results ----------")
for currDoc in allDocs :
    print (currDoc.title, currDoc.nameFormats, "directory matches: ", currDoc.dirMatches)
    print (currDoc.title, currDoc.nameFormats, "     file matches: ", currDoc.fileMatches)

Below is the output from the last print statement which shows the same values for both instances:

------- Results ----------
RFI RFI*[0-999]* directory matches:  ['RFI#04 Blah']
RFI RFI*[0-999]*      file matches:  ['CCO#02 Blah.pdf', 'CCO#01 Blah.pdf', 'RFI #1.pdf', 'RFI #2.pdf', 'RFI #3.pdf']
CCO CCO*[0-999]* directory matches:  ['RFI#04 Blah']
CCO CCO*[0-999]*      file matches:  ['CCO#02 Blah.pdf', 'CCO#01 Blah.pdf', 'RFI #1.pdf', 'RFI #2.pdf', 'RFI #3.pdf']

Vladimir Lagunov · Accepted Answer · 2013-05-27 15:58:03Z

1

This is because title, nameFormats etc. are static. These objects shared between all instances of Docs. If you want to each instance has its own lists then create them in constructor:

class Docs :
    def __init__ (self, inTitle, inFormats):
        self.title = inTitle
        self.nameFormats = inFormats
        self.title = []
        self.nameFormats = []
        self.fileMatches = []
        self.dirMatches = []

answered May 27, 2013 at 15:58

Vladimir Lagunov

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1 Comment

buttonsrtoys Over a year ago

Ah. That worked. Many thanks. The only tweak I made was "self.title" and "self.nameFormats" are defined twice in your sample code. Was that a typo or am I missing something?

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