diff -r 000000000000 -r c8e21d7dd685 src/pyams_utils/list.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/pyams_utils/list.py	Wed Dec 05 12:45:56 2018 +0100
@@ -0,0 +1,125 @@
+#
+# Copyright (c) 2008-2015 Thierry Florac <tflorac AT ulthar.net>
+# All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+#
+
+__docformat__ = 'restructuredtext'
+
+
+# import standard library
+from itertools import filterfalse
+from random import random, shuffle
+
+# import interfaces
+
+# import packages
+
+
+def unique(seq, key=None):
+    """Extract unique values from list, preserving order
+
+    :param iterator seq: input list
+    :param callable key: an identity function which is used to get 'identity' value of each element
+        in the list
+    :return: list; a new list containing only unique elements of the original list in their initial order.
+        Original list is not modified.
+
+    >>> from pyams_utils.list import unique
+    >>> mylist = [1, 2, 3, 2, 1]
+    >>> unique(mylist)
+    [1, 2, 3]
+
+    >>> mylist = [3, 2, 2, 1, 4, 2]
+    >>> unique(mylist)
+    [3, 2, 1, 4]
+
+    You can also set an 'id' function applied on each element:
+
+    >>> mylist = [1, 2, 3, '2', 4]
+    >>> unique(mylist, key=str)
+    [1, 2, 3, 4]
+    >>> mylist = ['A', 'B', 'b', '2', 4]
+    >>> unique(mylist, key=lambda x: str(x).lower())
+    ['A', 'B', '2', 4]
+    """
+    seen = set()
+    seen_add = seen.add
+    result = []
+    if key is None:
+        for element in filterfalse(seen.__contains__, seq):
+            seen_add(element)
+            result.append(element)
+    else:
+        for element in seq:
+            k = key(element)
+            if k not in seen:
+                seen_add(k)
+                result.append(element)
+    return result
+
+
+def unique_iter(iterable, key=None):
+    """Iterate over iterator values, yielding only unique values
+
+    :param iterator iterable: input iterator
+    :param callable key: an identity function which is used to get 'identity' value of each element
+        in the list
+    :return: an iterator of unique values
+
+    >>> from pyams_utils.list import unique_iter
+    >>> mylist = [1, 2, 3, 2, 1]
+    >>> list(unique_iter(mylist))
+    [1, 2, 3]
+
+    >>> mylist = [3, 2, 2, 1, 4, 2]
+    >>> list(unique_iter(mylist))
+    [3, 2, 1, 4]
+
+    You can also set an 'id' function applied on each element:
+
+    >>> mylist = [1, 2, 3, '2', 4]
+    >>> list(unique_iter(mylist, key=str))
+    [1, 2, 3, 4]
+    >>> mylist = ['A', 'B', 'b', '2', 4]
+    >>> list(unique_iter(mylist, key=lambda x: str(x).lower()))
+    ['A', 'B', '2', 4]
+    """
+    seen = set()
+    seen_add = seen.add
+    if key is None:
+        for element in filterfalse(seen.__contains__, iterable):
+            seen_add(element)
+            yield element
+    else:
+        for element in iterable:
+            k = key(element)
+            if k not in seen:
+                seen_add(k)
+                yield element
+
+
+def random_iter(iterable, limit=1):
+    """Get items randomly from an iterator
+
+    >>> from pyams_utils.list import random_iter
+    >>> mylist = [1, 2, 3, 2, 1]
+    >>> list(random_iter(mylist, 2))
+    [..., ...]
+    """
+    selected = [None] * limit
+    for index, item in enumerate(iterable):
+        if index < limit:
+            selected[index] = item
+        else:
+            selected_index = int(random() * (index+1))
+            if selected_index < limit:
+                selected[selected_index] = item
+    shuffle(selected)
+    return iter(selected)