관리-도구

편집 파일: recipes.py

"""Imported from the recipes section of the itertools documentation.

All functions taken from the recipes section of the itertools library docs
[1]_.
Some backward-compatible usability improvements have been made.

.. [1] http://docs.python.org/library/itertools.html#recipes

"""
import warnings
from collections import deque
from itertools import (
    chain,
    combinations,
    count,
    cycle,
    groupby,
    islice,
    repeat,
    starmap,
    tee,
    zip_longest,
)
import operator
from random import randrange, sample, choice

__all__ = [
    'all_equal',
    'consume',
    'convolve',
    'dotproduct',
    'first_true',
    'flatten',
    'grouper',
    'iter_except',
    'ncycles',
    'nth',
    'nth_combination',
    'padnone',
    'pad_none',
    'pairwise',
    'partition',
    'powerset',
    'prepend',
    'quantify',
    'random_combination_with_replacement',
    'random_combination',
    'random_permutation',
    'random_product',
    'repeatfunc',
    'roundrobin',
    'tabulate',
    'tail',
    'take',
    'unique_everseen',
    'unique_justseen',
]

def take(n, iterable):
    """Return first *n* items of the iterable as a list.

>>> take(3, range(10))
        [0, 1, 2]

If there are fewer than *n* items in the iterable, all of them are
    returned.

>>> take(10, range(3))
        [0, 1, 2]

"""
    return list(islice(iterable, n))

def tabulate(function, start=0):
    """Return an iterator over the results of ``func(start)``,
    ``func(start + 1)``, ``func(start + 2)``...

*func* should be a function that accepts one integer argument.

If *start* is not specified it defaults to 0. It will be incremented each
    time the iterator is advanced.

>>> square = lambda x: x ** 2
        >>> iterator = tabulate(square, -3)
        >>> take(4, iterator)
        [9, 4, 1, 0]

"""
    return map(function, count(start))

def tail(n, iterable):
    """Return an iterator over the last *n* items of *iterable*.

>>> t = tail(3, 'ABCDEFG')
    >>> list(t)
    ['E', 'F', 'G']

"""
    return iter(deque(iterable, maxlen=n))

def consume(iterator, n=None):
    """Advance *iterable* by *n* steps. If *n* is ``None``, consume it
    entirely.

Efficiently exhausts an iterator without returning values. Defaults to
    consuming the whole iterator, but an optional second argument may be
    provided to limit consumption.

>>> i = (x for x in range(10))
        >>> next(i)
        0
        >>> consume(i, 3)
        >>> next(i)
        4
        >>> consume(i)
        >>> next(i)
        Traceback (most recent call last):
          File "<stdin>", line 1, in <module>
        StopIteration

If the iterator has fewer items remaining than the provided limit, the
    whole iterator will be consumed.

>>> i = (x for x in range(3))
        >>> consume(i, 5)
        >>> next(i)
        Traceback (most recent call last):
          File "<stdin>", line 1, in <module>
        StopIteration

"""
    # Use functions that consume iterators at C speed.
    if n is None:
        # feed the entire iterator into a zero-length deque
        deque(iterator, maxlen=0)
    else:
        # advance to the empty slice starting at position n
        next(islice(iterator, n, n), None)

def nth(iterable, n, default=None):
    """Returns the nth item or a default value.

>>> l = range(10)
    >>> nth(l, 3)
    3
    >>> nth(l, 20, "zebra")
    'zebra'

"""
    return next(islice(iterable, n, None), default)

def all_equal(iterable):
    """
    Returns ``True`` if all the elements are equal to each other.

>>> all_equal('aaaa')
        True
        >>> all_equal('aaab')
        False

"""
    g = groupby(iterable)
    return next(g, True) and not next(g, False)

def quantify(iterable, pred=bool):
    """Return the how many times the predicate is true.

>>> quantify([True, False, True])
    2

"""
    return sum(map(pred, iterable))

def pad_none(iterable):
    """Returns the sequence of elements and then returns ``None`` indefinitely.

>>> take(5, pad_none(range(3)))
        [0, 1, 2, None, None]

Useful for emulating the behavior of the built-in :func:`map` function.