Collection Operations

extepy.groupby(values, by)

Partition values into several groups, and return a dict.

Parameters:

• values (iterable)

• by (callable) – The function to get the group of a value.

Returns:

groups (dict[hashable, list])

Raises:

TypeError – Raises when a return value of by() is not hashable.

Examples

>>> groupby(range(10), lambda x: x % 3)
{0: [0, 3, 6, 9], 1: [1, 4, 7], 2: [2, 5, 8]}

>>> groupby([0, "", False, float('nan'), "Hello"], by=bool)
{False: [0, '', False], True: [nan, 'Hello']}

extepy.partition(values, by, count=None)

Partition values into several groups, and return lists.

Parameters:

• values (iterable)

• by (callable) – Function to get the group index of a value. Its return value will be wrapped by int().

• count (int, Optional) – Number of groups.

Return type:

results (list[list])

Examples

>>> partition(range(10), by=lambda x: x % 3)
[[0, 3, 6, 9], [1, 4, 7], [2, 5, 8]]

Specify the number of groups.

>>> partition([0, "", False, float('nan'), "Hello"], by=bool, count=3)
[[0, '', False], [nan, 'Hello'], []]

Raise error when the group index exceeds range.

>>> partition([-1, 1], by=int)
Traceback (most recent call last):
...
ValueError: Group index should be >= 0.