toil.lib.iterables

Module Contents

Classes

concat

A literal iterable to combine sequence literals (lists, set) with generators or list comprehensions.

Functions

flatten(iterables)

Flatten an iterable, except for string elements.

Attributes

IT

toil.lib.iterables.IT

toil.lib.iterables.flatten(iterables)

Flatten an iterable, except for string elements.

Parameters:

iterables (Iterable[IT])

Return type:

Iterator[IT]

class toil.lib.iterables.concat(*args)

A literal iterable to combine sequence literals (lists, set) with generators or list comprehensions.

Instead of

>>> [ -1 ] + [ x * 2 for x in range( 3 ) ] + [ -1 ]
[-1, 0, 2, 4, -1]

you can write

>>> list( concat( -1, ( x * 2 for x in range( 3 ) ), -1 ) )
[-1, 0, 2, 4, -1]

This is slightly shorter (not counting the list constructor) and does not involve array construction or concatenation.

Note that concat() flattens (or chains) all iterable arguments into a single result iterable:

>>> list( concat( 1, range( 2, 4 ), 4 ) )
[1, 2, 3, 4]

It only does so one level deep. If you need to recursively flatten a data structure, check out crush().

If you want to prevent that flattening for an iterable argument, wrap it in concat():

>>> list( concat( 1, concat( range( 2, 4 ) ), 4 ) )
[1, range(2, 4), 4]

Some more example.

>>> list( concat() ) # empty concat
[]
>>> list( concat( 1 ) ) # non-iterable
[1]
>>> list( concat( concat() ) ) # empty iterable
[]
>>> list( concat( concat( 1 ) ) ) # singleton iterable
[1]
>>> list( concat( 1, concat( 2 ), 3 ) ) # flattened iterable
[1, 2, 3]
>>> list( concat( 1, [2], 3 ) ) # flattened iterable
[1, 2, 3]
>>> list( concat( 1, concat( [2] ), 3 ) ) # protecting an iterable from being flattened
[1, [2], 3]
>>> list( concat( 1, concat( [2], 3 ), 4 ) ) # protection only works with a single argument
[1, 2, 3, 4]
>>> list( concat( 1, 2, concat( 3, 4 ), 5, 6 ) )
[1, 2, 3, 4, 5, 6]
>>> list( concat( 1, 2, concat( [ 3, 4 ] ), 5, 6 ) )
[1, 2, [3, 4], 5, 6]

Note that while strings are technically iterable, concat() does not flatten them.

>>> list( concat( 'ab' ) )
['ab']
>>> list( concat( concat( 'ab' ) ) )
['ab']

Parameters:

args (Any)

__iter__()

Return type:

Iterator[Any]