Rails5 - ruby 2.2.3 // ActiveSupport :: TimeZone如何变化？(Rails5 - ruby 2.2.3 // how ActiveSupport::TimeZone changed?)

 您可以使用“ 如何从列表中删除重复项”中的set方法，同时保留顺序？ ，使用x[1]作为唯一标识符： 
 
def unique_second_element(seq):
    seen = set()
    seen_add = seen.add
    return [x for x in seq if not (x[1] in seen or seen_add(x[1]))]
 
 请注意，如果您想保留最后一次出现， OrderedDict方法也会显示; 对于第一次发生，您必须将输入反向，然后再次反向输出。 
 
 您可以通过支持key功能使其更加通用： 
 
def unique_preserve_order(seq, key=None):
    if key is None:
        key = lambda elem: elem
    seen = set()
    seen_add = seen.add
    augmented = ((key(x), x) for x in seq)
    return [x for k, x in augmented if not (k in seen or seen_add(k))]
 
 然后使用 
 
import operator

unique_preserve_order(yourlist, key=operator.itemgetter(1))
 
 演示： 
 
>>> def unique_preserve_order(seq, key=None):
...     if key is None:
...         key = lambda elem: elem
...     seen = set()
...     seen_add = seen.add
...     augmented = ((key(x), x) for x in seq)
...     return [x for k, x in augmented if not (k in seen or seen_add(k))]
... 
>>> from pprint import pprint
>>> import operator
>>> yourlist = [(67, u'top-coldestcitiesinamerica'), (66, u'ecofriendlyideastocelebrateindependenceday-phpapp'), (65, u'a-b-c-ca-d-ab-ea-d-c-c'), (64, u'a-b-c-ca-d-ab-ea-d-c-c'), (63, u'alexandre-meybeck-faowhatisclimate-smartagriculture-backgroundopportunitiesandchallenges'), (62, u'ghgemissions'), (61, u'top-coldestcitiesinamerica'), (58, u'infographicthe-stateofdigitaltransformationaltimetergroup'), (57, u'culture'), (55, u'cas-k-ihaveanidea'), (54, u'trendsfor'), (53, u'batteryimpedance'), (52, u'evs-howey-full'), (51, u'bericht'), (49, u'classiccarinsurance'), (47, u'uploaded_file'), (46, u'x_file'), (45, u's-s-main'), (44, u'vehicle-propulsion'), (43, u'x_file')]
>>> pprint(unique_preserve_order(yourlist, operator.itemgetter(1)))
[(67, u'top-coldestcitiesinamerica'),
 (66, u'ecofriendlyideastocelebrateindependenceday-phpapp'),
 (65, u'a-b-c-ca-d-ab-ea-d-c-c'),
 (63,
  u'alexandre-meybeck-faowhatisclimate-smartagriculture-backgroundopportunitiesandchallenges'),
 (62, u'ghgemissions'),
 (58, u'infographicthe-stateofdigitaltransformationaltimetergroup'),
 (57, u'culture'),
 (55, u'cas-k-ihaveanidea'),
 (54, u'trendsfor'),
 (53, u'batteryimpedance'),
 (52, u'evs-howey-full'),
 (51, u'bericht'),
 (49, u'classiccarinsurance'),
 (47, u'uploaded_file'),
 (46, u'x_file'),
 (45, u's-s-main'),
 (44, u'vehicle-propulsion')]

You could use the set approach from How do you remove duplicates from a list in whilst preserving order?, using x[1] as the unique identifier:
 
def unique_second_element(seq):
    seen = set()
    seen_add = seen.add
    return [x for x in seq if not (x[1] in seen or seen_add(x[1]))]
 
Note that the OrderedDict approach also shown would also work if you wanted to preserve the last occurrence; for a first occurrence you'd have to reverse the input then reverse again for the output.
 
You could make this even more generic by supporting a key function:
 
def unique_preserve_order(seq, key=None):
    if key is None:
        key = lambda elem: elem
    seen = set()
    seen_add = seen.add
    augmented = ((key(x), x) for x in seq)
    return [x for k, x in augmented if not (k in seen or seen_add(k))]
 
then use
 
import operator

unique_preserve_order(yourlist, key=operator.itemgetter(1))
 
Demo:
 
>>> def unique_preserve_order(seq, key=None):
...     if key is None:
...         key = lambda elem: elem
...     seen = set()
...     seen_add = seen.add
...     augmented = ((key(x), x) for x in seq)
...     return [x for k, x in augmented if not (k in seen or seen_add(k))]
... 
>>> from pprint import pprint
>>> import operator
>>> yourlist = [(67, u'top-coldestcitiesinamerica'), (66, u'ecofriendlyideastocelebrateindependenceday-phpapp'), (65, u'a-b-c-ca-d-ab-ea-d-c-c'), (64, u'a-b-c-ca-d-ab-ea-d-c-c'), (63, u'alexandre-meybeck-faowhatisclimate-smartagriculture-backgroundopportunitiesandchallenges'), (62, u'ghgemissions'), (61, u'top-coldestcitiesinamerica'), (58, u'infographicthe-stateofdigitaltransformationaltimetergroup'), (57, u'culture'), (55, u'cas-k-ihaveanidea'), (54, u'trendsfor'), (53, u'batteryimpedance'), (52, u'evs-howey-full'), (51, u'bericht'), (49, u'classiccarinsurance'), (47, u'uploaded_file'), (46, u'x_file'), (45, u's-s-main'), (44, u'vehicle-propulsion'), (43, u'x_file')]
>>> pprint(unique_preserve_order(yourlist, operator.itemgetter(1)))
[(67, u'top-coldestcitiesinamerica'),
 (66, u'ecofriendlyideastocelebrateindependenceday-phpapp'),
 (65, u'a-b-c-ca-d-ab-ea-d-c-c'),
 (63,
  u'alexandre-meybeck-faowhatisclimate-smartagriculture-backgroundopportunitiesandchallenges'),
 (62, u'ghgemissions'),
 (58, u'infographicthe-stateofdigitaltransformationaltimetergroup'),
 (57, u'culture'),
 (55, u'cas-k-ihaveanidea'),
 (54, u'trendsfor'),
 (53, u'batteryimpedance'),
 (52, u'evs-howey-full'),
 (51, u'bericht'),
 (49, u'classiccarinsurance'),
 (47, u'uploaded_file'),
 (46, u'x_file'),
 (45, u's-s-main'),
 (44, u'vehicle-propulsion')]