Source code for toil.lib.iterables

# Copyright (C) 2015-2021 Regents of the University of California
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#     http://www.apache.org/licenses/LICENSE-2.0
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# 5.14.2018: copied into Toil from https://github.com/BD2KGenomics/bd2k-python-lib
from typing import Any, Iterable, Iterator, TypeVar

IT = TypeVar("IT")


[docs] def flatten(iterables: Iterable[IT]) -> Iterator[IT]: """Flatten an iterable, except for string elements.""" for it in iterables: if isinstance(it, str): yield it else: yield from it
# noinspection PyPep8Naming
[docs] class concat: """ 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'] """ def __init__(self, *args: Any) -> None: super().__init__() self.args = args
[docs] def __iter__(self) -> Iterator[Any]: def expand(x): if isinstance(x, concat) and len(x.args) == 1: i = x.args elif not isinstance(x, str): try: i = x.__iter__() except AttributeError: i = x, else: i = x return i return flatten(map(expand, self.args))