Python IOError: Errno 13 Permission denied

Question

Ok, I'm totally baffled. I've been working on this all night and I can't get it to work. I have premission to look into the file, all I want to do is read the darn thing. Every time I try I get:

Traceback (most recent call last):
  File "<pyshell#3>", line 1, in <module>
    scan('test', rules, 0)
  File "C:\Python32\PythonStuff\csc242hw7\csc242hw7.py", line 45, in scan
    files = open(n, 'r')
IOError: [Errno 13] Permission denied: 'test\\test'

Here is my code. It's unfinished but I feel I should at least be getting correct values for the sections I am testing. Basically I want to look into a folder, and if there is a file scan it looking for whatever I set my signatures to. If there are folders I will or will not scan them depending on the depth specified. If there is a depth < 0 then it will return. If depth == 0 then it will just scan the elements in the first folder. If depth > 0 it will scan folders up until the specified depth. None of that matters thought, because for whatever reason I don't have permission to read the file. I have no idea what I am doing wrong.

def scan(pathname, signatures, depth):
'''Recusively scans all the files contained in the folder pathname up
until the specificed depth'''
    # Reconstruct this!
    if depth < 0:
        return
    elif depth == 0:
        for item in os.listdir(pathname):
            n = os.path.join(pathname, item)
            try:
                # List a directory on n
                scan(n, signatures, depth)
            except:
                # Do what you should for a file
                files = open(n, 'r')
                text = file.read()
                for virus in signatures:
                    if text.find(signatures[virus]) > 0:
                        print('{}, found virus {}'.format(n, virus))
                files.close()

Just a quick edit:

This code below does something very similar, but I can't control the depth. It however, works fine.

def oldscan(pathname, signatures):
    '''recursively scans all files contained, directly or
       indirectly, in the folder pathname'''
    for item in os.listdir(pathname):
        n = os.path.join(pathname, item)
        try:
            oldscan(n, signatures)
        except:
            f = open(n, 'r')
            s = f.read()
            for virus in signatures:
                if s.find(signatures[virus]) > 0:
                    print('{}, found virus {}'.format(n,virus))
            f.close()

Answer 1

I venture to guess that test\test is a directory, and some exception occurred. You catch the exception blindly and try to open the directory as a file. That gives Errno 13 on Windows.

Use os.path.isdir to distinguish between files and directories, instead of the try...except.

    for item in os.listdir(pathname):
        n = os.path.join(pathname, item)
        if os.path.isdir(n):
            # List a directory on n
            scan(n, signatures, depth)
        else:
            # Do what you should for a file