python-stream (simplestream)

Stream pipeline API with lazy evaluation inspired by Java 8

Install

pip install simplestream

Example 1

>>> from stream import Stream
>>>
>>> l = Stream(range(10))\
...     .filter(lambda x: x % 2 == 0)\
...     .map(lambda x: x ** 2)\
...     .collect(list)
>>> print(l)
[0, 4, 16, 36, 64]
>>>

Example 2

>>> from stream import Stream
>>>
>>> s = Stream('Hello').collect(','.join)
>>> print(s)
H,e,l,l,o
>>>

Example 3

>>> from stream import Stream
>>>
>>> s1 = Stream(range(5))\
...     .map(lambda x: x * 2)
>>> s2 = Stream(range(3))\
...     .flatmap(range)
>>> Stream.chain(s1, s2).collect(list)
[0, 2, 4, 6, 8, 0, 0, 1]
>>>

APIs

Transformations

• map
• filter
• flatten
• flatmap
• distinct
• limit
• skip
• chain

Actions

• all
• any
• none
• min
• max
• count
• reduce
• foreach
• collect

Note

• Every stream API is lazily evaluated, so until you call action API, functions you passed to transformations will not be called.
• Unlike Java 8 Stream API, min and max get key function instead of comparator.
• Instead of concat, simplestream provides chain method which gets arbitrary number of streams.