pythonic tree-walking idioms

[raskol at hushmail.com]

Hey folks,

curious non-comp-sci perpetual newbie looking for particularly pythonic
tree-walking idioms to study...

I've scoured the source of the standard 2.1 library and discovered
os.path.walk() and Ping's walktree() in inspect.py as well as the wicked
TreeWalker.py in the xml.dom package (first two included for reference,
latter not included [it's scary, damnit!])

Are there any other examples for doing this kind of stuff?


Thanks in advance,


Shak 
raskol at hushmail.com


# -----------------------------------------------------------------------
# os.path tree-walking
# -----------------------------------------------------------------------
# Directory tree walk.
# For each directory under top (including top itself, but excluding
# '.' and '..'), func(arg, dirname, filenames) is called, where
# dirname is the name of the directory and filenames is the list
# files files (and subdirectories etc.) in the directory.
# The func may modify the filenames list, to implement a filter,
# or to impose a different order of visiting.

def walk(top, func, arg):
    """Directory tree walk whth callback function.

    walk(top, func, arg) calls func(arg, d, files) for each directory d
    in the tree rooted at top (including top itself); files is a list
    of all the files and subdirs in directory d."""
    try:
        names = os.listdir(top)
    except os.error:
        return
    func(arg, top, names)
    exceptions = ('.', '..')
    for name in names:
        if name not in exceptions:
            name = join(top, name)
            if isdir(name):
                walk(name, func, arg)



# -----------------------------------------------------------------------
# inspect.py tree walking
# -----------------------------------------------------------------------
def walktree(classes, children, parent):
    """Recursive helper function for getclasstree()."""
    results = []
    classes.sort(lambda a, b: cmp(a.__name__, b.__name__))
    for c in classes:
        results.append((c, c.__bases__))
        if children.has_key(c):
            results.append(walktree(children[c], children, c))
    return results

def getclasstree(classes, unique=0):
    """Arrange the given list of classes into a hierarchy of nested
lists.

    Where a nested list appears, it contains classes derived from the class
    whose entry immediately precedes the list.  Each entry is a 2-tuple
    containing a class and a tuple of its base classes.  If the 'unique'
    argument is true, exactly one entry appears in the returned structure
    for each class in the given list.  Otherwise, classes using multiple
    inheritance and their descendants will appear multiple
times."""
    children = {}
    roots = []
    for c in classes:
        if c.__bases__:
            for parent in c.__bases__:
                if not children.has_key(parent):
                    children[parent] = []
                children[parent].append(c)
                if unique and parent in classes: break
        elif c not in roots:
            roots.append(c)
    for parent in children.keys():
        if parent not in classes:
            roots.append(parent)
    return walktree(roots, children, None)




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