iterator-chain

Chain together lazily computed modifications to iterators.

One normally needs to do the following

list(map(lambda element: element / 3,
filter(lambda element: element > 32,
map(lambda element: element * 2, [5, 78, 12, 26]))))

Instead do this

iterator_chain.from_iterable([5, 78, 12, 26]) \
.map(lambda element: element * 2) \
.filter(lambda element: element > 32) \
.map(lambda element: element / 3).list()

It allows the developer to read the code in a more natural fashion: from left to right and from top to bottom. The developer no longer needs to "unwrap" the functions to understand the logic.

Install

Include iterator-chain in your requirements.txt file and/or use pip to install it.

$ pip install iterator-chain

API

Start by importing the package.

import iterator_chain

Start the chain

To start the chain, use the from_iterable or from_iterable_parallel function. They take an iterable.

an_iterable = [5, 78, 12, 26]
chain = iterator_chain.from_iterable(an_iterable)
parallel_chain = iterator_chain.from_iterable_parallel(an_iterable)

Continuing the chain

From there, one can call a plethora of additional methods to modify the iterable passed in originally. The methods are outlined below. The methods fall into one of two categories: chaining or terminating.

• Chaining methods apply some modification to the elements in the iterator, but keeps the chain alive. This allows additional chaining methods to be subsequently called on the result. Because modifications are lazily computed, none of the modifications from chaining methods are applied until after a terminating method is called.
• Terminating methods also apply some modification, requests some information, or executes something on the elements in the iterator. They stop the chaining by returning an actual value. This value will depend on all the previous chaining methods being executed first.

Chaining methods

Parallel Versions

Terminating methods

Parallel Versions

Examples

import iterator_chain
an_iterable = [5, 78, 12, 26]
iterator_chain.from_iterable(an_iterable) \  #starts the chain
    .map(lambda element: element * 2) \  #multiplies every element by two: [10, 156, 24, 52]
    .filter(lambda element: element > 32) \  #keeps any element greater than 32: [156, 52]
    .map(lambda element: element / 3) \ #divides every element by three: [52.0, 17.333333333333332]
    .list()  #and finally returns a list of the result for later use in your application: [52.0, 17.333333333333332]