add

ccxt/static_dependencies/toolz/recipes.py

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+import itertools
+from .itertoolz import frequencies, pluck, getter
+
+
+__all__ = ('countby', 'partitionby')
+
+
+def countby(key, seq):
+    """ Count elements of a collection by a key function
+
+    >>> countby(len, ['cat', 'mouse', 'dog'])
+    {3: 2, 5: 1}
+
+    >>> def iseven(x): return x % 2 == 0
+    >>> countby(iseven, [1, 2, 3])  # doctest:+SKIP
+    {True: 1, False: 2}
+
+    See Also:
+        groupby
+    """
+    if not callable(key):
+        key = getter(key)
+    return frequencies(map(key, seq))
+
+
+def partitionby(func, seq):
+    """ Partition a sequence according to a function
+
+    Partition `s` into a sequence of lists such that, when traversing
+    `s`, every time the output of `func` changes a new list is started
+    and that and subsequent items are collected into that list.
+
+    >>> is_space = lambda c: c == " "
+    >>> list(partitionby(is_space, "I have space"))
+    [('I',), (' ',), ('h', 'a', 'v', 'e'), (' ',), ('s', 'p', 'a', 'c', 'e')]
+
+    >>> is_large = lambda x: x > 10
+    >>> list(partitionby(is_large, [1, 2, 1, 99, 88, 33, 99, -1, 5]))
+    [(1, 2, 1), (99, 88, 33, 99), (-1, 5)]
+
+    See also:
+        partition
+        groupby
+        itertools.groupby
+    """
+    return map(tuple, pluck(1, itertools.groupby(seq, key=func)))