Streams

Streams are iterables which are used when you are dealing with large, possibly infinite data. Streams are preferred over normal iterables like list and tuple because streams only need to make one pass over itself in order to update it. Enums behave as follows:

def myprint(x):
    print(x)
    return x
    
>>> e = func.enum([1, 2, 3])
>>> (e.pipe(func.enum.map, myprint)
      .pipe(func.enum.map, lambda x: x * 2)
      .pipe(func.enum.map, myprint))
1
2
3
2
4
6
[2, 4, 6]

Streams, on the other hand, behave like so:

def myprint(x):
    print(x)
    return x
    
>>> s = func.stream(lambda x: x)
>>> new_s = (s.pipe(func.stream.map, myprint)
              .pipe(func.stream.map, lambda x: x * 2)
              .pipe(func.stream.map, myprint))

Nothing is printed. This is because streams only evaluate themselves when an eager function is applied:

>>> func.enum.take(new_s, 3)
1
2
2
4
3
6
[2, 4, 6]

Note that the order is different. This is because the stream is making only one pass; it evaluates all the functions on a single element before moving on to the next one. This makes streams a very efficient iterable.