1 files changed, 105 insertions, 0 deletions
diff --git a/osdf/utils/programming_utils.py b/osdf/utils/programming_utils.py
new file mode 100644
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+++ b/osdf/utils/programming_utils.py
@@ -0,0 +1,105 @@
+# -------------------------------------------------------------------------
+#   Copyright (c) 2015-2017 AT&T Intellectual Property
+#
+#   Licensed under the Apache License, Version 2.0 (the "License");
+#   you may not use this file except in compliance with the License.
+#   You may obtain a copy of the License at
+#
+#       http://www.apache.org/licenses/LICENSE-2.0
+#
+#   Unless required by applicable law or agreed to in writing, software
+#   distributed under the License is distributed on an "AS IS" BASIS,
+#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#   See the License for the specific language governing permissions and
+#   limitations under the License.
+#
+# -------------------------------------------------------------------------
+#
+
+import collections
+import itertools
+
+
+class DotDict(dict):
+    """A dot-dict mixin to be able to access a dictionary via dot notation
+    source: https://stackoverflow.com/questions/2352181/how-to-use-a-dot-to-access-members-of-dictionary
+    """
+    __getattr__ = dict.get
+    __setattr__ = dict.__setitem__
+    __delattr__ = dict.__delitem__
+
+
+class MetaSingleton(type):
+    """Singleton class (2nd Chapter) from Learning Python Design Patterns - 2nd ed.
+    Chetan Giridhar, Packt Publ. 2016"""
+    _instances = {}
+
+    def __call__(cls, *args, **kwargs):
+        if cls not in cls._instances:
+            cls._instances[cls] = super(MetaSingleton, cls).__call__(*args, **kwargs)
+        return cls._instances[cls]
+
+
+def namedtuple_with_defaults(typename, field_names, default_values=()):
+    """A namedtuple with default values -- Stack overflow recipe from Mark Lodato
+    http://stackoverflow.com/questions/11351032/named-tuple-and-optional-keyword-arguments
+    :param typename: Name for the class (same as for namedtuple)
+    :param field_names: Field names (same as for namedtuple)
+    :param default_values: Can be specified as a dictionary or as a list
+    :return: New namedtuple object
+    """
+    T = collections.namedtuple(typename, field_names)
+    T.__new__.__defaults__ = (None,) * len(T._fields)
+    if isinstance(default_values, collections.Mapping):
+        prototype = T(**default_values)
+    else:
+        prototype = T(*default_values)
+    T.__new__.__defaults__ = tuple(prototype)
+    return T
+
+
+def dot_notation(dict_like, dot_spec):
+    """Return the value corresponding to the dot_spec from a dict_like object
+    :param dict_like: dictionary, JSON, etc.
+    :param dot_spec: a dot notation (e.g. a1.b1.c1.d1 => a1["b1"]["c1"]["d1"])
+    :return: the value referenced by the dot_spec
+    """
+    attrs = dot_spec.split(".")  # we split the path
+    parent = dict_like.get(attrs[0])
+    children = ".".join(attrs[1:])
+    if not (parent and children):  # if no children or no parent, bail out
+        return parent
+    if isinstance(parent, list):  # here, we apply remaining path spec to all children
+        return [dot_notation(j, children) for j in parent]
+    elif isinstance(parent, dict):
+        return dot_notation(parent, children)
+    else:
+        return None
+
+
+def list_flatten(l):
+    """
+    Flatten a complex nested list of nested lists into a flat list (DFS).
+    For example, [ [1, 2], [[[2,3,4], [2,3,4]], [3,4,5, 'hello']]]
+    will produce [1, 2, 2, 3, 4, 2, 3, 4, 3, 4, 5, 'hello']
+    """
+    return list(itertools.chain(*[list_flatten(j) if isinstance(j, list) else [j] for j in l]))
+
+
+def inverted_dict(keys: list, key_val_dict: dict) -> dict:
+    """
+    Get val -> [keys] mapping for the given keys using key_val_dict
+    :param keys: the keys we are interested in (a list)
+    :param key_val_dict: the key -> val mapping
+    :return: inverted dictionary of val -> [keys] (for the subset dict of given keys)
+    """
+    res = {}
+    all_tuples = ((k, key_val_dict[k] if k in key_val_dict else 'no-parent-' + k) for k in keys)
+    for k, v in all_tuples:
+        if v in res:
+            res[v].append(k)
+        else:
+            res[v] = [k]
+    # making sure to remove duplicate keys
+    res = dict((v, list(set(k_list))) for v, k_list in res.items())
+    return res