Synnefo

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def lookup_path(container, path, sep='.', createpath=False):

    """

    return (['a','b'],

            [container['a'], container['a']['b']],

            'c')  where path=sep.join(['a','b','c'])

    """

    names = path.split(sep)

    dirnames = names[:-1]

    basename = names[-1]

    node = container

    name_path = []

    node_path = [node]

    for name in dirnames:

        name_path.append(name)

        if name not in node:

            if not createpath:

                m = "'{0}': path not found".format(sep.join(name_path))

                raise KeyError(m)

            node[name] = {}

        try:

            node = node[name]

        except TypeError as e:

            m = "'{0}': cannot traverse path beyond this node: {1}"

            m = m.format(sep.join(name_path), str(e))

            raise ValueError(m)

        node_path.append(node)

    return name_path, node_path, basename

def walk_paths(container):

    for name, node in container.iteritems():

        if not hasattr(node, 'items'):

            yield [name], [node]

        else:

            for names, nodes in walk_paths(node):

                yield [name] + names, [node] + nodes

def list_paths(container, sep='.'):

    """

    >>> sorted(list_paths({'a': {'b': {'c': 'd'}}}))

    [('a.b.c', 'd')]

    >>> sorted(list_paths({'a': {'b': {'c': 'd'}, 'e': 3}}))

    [('a.b.c', 'd'), ('a.e', 3)]

    >>> sorted(list_paths({'a': {'b': {'c': 'd'}, 'e': {'f': 3}}}))

    [('a.b.c', 'd'), ('a.e.f', 3)]

    >>> list_paths({})

    []

    """

    return [(sep.join(name_path), node_path[-1])

            for name_path, node_path in walk_paths(container)]

def del_path(container, path, sep='.', collect=True):

    """

    del container['a']['b']['c'] where path=sep.join(['a','b','c'])

    >>> d = {'a': {'b': {'c': 'd'}}}; del_path(d, 'a.b.c'); d

    {}

    >>> d = {'a': {'b': {'c': 'd'}}}; del_path(d, 'a.b.c', collect=False); d

    {'a': {'b': {}}}

    >>> d = {'a': {'b': {'c': 'd'}}}; del_path(d, 'a.b.c.d')

    Traceback (most recent call last):

    ValueError: 'a.b.c': cannot traverse path beyond this node:\

 'str' object does not support item deletion

    """

    name_path, node_path, basename = \

            lookup_path(container, path, sep=sep, createpath=False)

    lastnode = node_path.pop()

    lastname = basename

    try:

        if basename in lastnode:

            del lastnode[basename]

    except (TypeError, KeyError) as e:

        m = "'{0}': cannot traverse path beyond this node: {1}"

        m = m.format(sep.join(name_path), str(e))

        raise ValueError(m)

    if collect:

        while node_path and not lastnode:

            basename = name_path.pop()

            lastnode = node_path.pop()

            del lastnode[basename]

def get_path(container, path, sep='.'):

    """

    return container['a']['b']['c'] where path=sep.join(['a','b','c'])

    >>> get_path({'a': {'b': {'c': 'd'}}}, 'a.b.c.d')

    Traceback (most recent call last):

    ValueError: 'a.b.c.d': cannot traverse path beyond this node:\

 string indices must be integers, not str

    >>> get_path({'a': {'b': {'c': 1}}}, 'a.b.c.d')

    Traceback (most recent call last):

    ValueError: 'a.b.c.d': cannot traverse path beyond this node:\

 'int' object is unsubscriptable

    >>> get_path({'a': {'b': {'c': 1}}}, 'a.b.c')

    1

    >>> get_path({'a': {'b': {'c': 1}}}, 'a.b')

    {'c': 1}

    """

    name_path, node_path, basename = \

            lookup_path(container, path, sep=sep, createpath=False)

    name_path.append(basename)

    node = node_path[-1]

    try:

        return node[basename]

    except TypeError as e:

        m = "'{0}': cannot traverse path beyond this node: {1}"

        m = m.format(sep.join(name_path), str(e))

        raise ValueError(m)

    except KeyError as e:

        m = "'{0}': path not found: {1}"

        m = m.format(sep.join(name_path), str(e))

        raise KeyError(m)

def set_path(container, path, value, sep='.',

             createpath=False, overwrite=True):

    """

    container['a']['b']['c'] = value where path=sep.join(['a','b','c'])

    >>> set_path({'a': {'b': {'c': 'd'}}}, 'a.b.c.d', 1)

    Traceback (most recent call last):

    ValueError: 'a.b.c.d': cannot traverse path beyond this node:\

 'str' object does not support item assignment

    >>> set_path({'a': {'b': {'c': 'd'}}}, 'a.b.x.d', 1)

    Traceback (most recent call last):

    KeyError: "'a.b.x': path not found"

    >>> set_path({'a': {'b': {'c': 'd'}}}, 'a.b.x.d', 1, createpath=True)

    >>> set_path({'a': {'b': {'c': 'd'}}}, 'a.b.c', 1)

    >>> set_path({'a': {'b': {'c': 'd'}}}, 'a.b.c', 1, overwrite=False)

    Traceback (most recent call last):

    ValueError: will not overwrite path 'a.b.c'

    """

    name_path, node_path, basename = \

            lookup_path(container, path, sep=sep, createpath=createpath)

    name_path.append(basename)

    node = node_path[-1]

    if basename in node and not overwrite:

        m = "will not overwrite path '{0}'".format(path)

        raise ValueError(m)

    try:

        node[basename] = value

    except TypeError as e:

        m = "'{0}': cannot traverse path beyond this node: {1}"

        m = m.format(sep.join(name_path), str(e))

        raise ValueError(m)

if __name__ == '__main__':

    import doctest

    doctest.testmod()