展平包含子列表的字符串列表

Question

我有一個strings list ，其中包含一個sublist os strings ：

ids = [u'spotify:track:3ftnDaaL02tMeOZBunIwls', u'spotify:track:4CKjTXDDWIrS0cwSA9scgk', [u'spotify:track:6oRbm1KOqskLTFc1rvGi5F',
u'spotify:track:045sp2JToyTaaKyXkGejPy']]

我試圖用以下方法使其變平：

[item for item in ids for item in sublist]

和

chain = itertools.chain(ids)

但是這些解決方案將字符串分開...

我如何將原始list拼合為

[u'spotify:track:3ftnDaaL02tMeOZBunIwls', u'spotify:track:4CKjTXDDWIrS0cwSA9scgk', u'spotify:track:6oRbm1KOqskLTFc1rvGi5F',u'spotify:track:045sp2JToyTaaKyXkGejPy']

？

Answer 1

您可以使用帶有isinstance檢查的簡單循環。

out = []
for i in ids:
    if isinstance(i, list):
        out.extend(i)
    else:
        out.append(i)

print(out)  

輸出：

['spotify:track:3ftnDaaL02tMeOZBunIwls',
 'spotify:track:4CKjTXDDWIrS0cwSA9scgk',
 'spotify:track:6oRbm1KOqskLTFc1rvGi5F',
 'spotify:track:045sp2JToyTaaKyXkGejPy'] 

---

您還可以使用itertools.chain ，但要多加一層預處理：

from itertools import chain

out = list(chain.from_iterable([i if isinstance(i, list) else [i] for i in ids]))
print(out)    

具有相同的輸出。

Answer 2

您只需要將任何字符串強制轉換為列表：

import itertools
ids = [u'spotify:track:3ftnDaaL02tMeOZBunIwls', u'spotify:track:4CKjTXDDWIrS0cwSA9scgk',   [u'spotify:track:6oRbm1KOqskLTFc1rvGi5F',
u'spotify:track:045sp2JToyTaaKyXkGejPy']]

new_data = list(itertools.chain.from_iterable([[i] if not isinstance(i, list) else i for i in b]))

輸出：

[u'spotify:track:3ftnDaaL02tMeOZBunIwls', u'spotify:track:4CKjTXDDWIrS0cwSA9scgk', u'spotify:track:6oRbm1KOqskLTFc1rvGi5F', u'spotify:track:045sp2JToyTaaKyXkGejPy']

Answer 3

您可以創建一個使列表變平的功能。

def flatten(lst):
  if isinstance(lst, (str, unicode)):
    return [lst]
  return [unit for item in lst for unit in flatten(item)]

print(flatten(ids))

Answer 4

你可以做：

>>> [x for l in ids for x in (l if isinstance(l, list) else [l])]
[u'spotify:track:3ftnDaaL02tMeOZBunIwls', u'spotify:track:4CKjTXDDWIrS0cwSA9scgk', u'spotify:track:6oRbm1KOqskLTFc1rvGi5F', u'spotify:track:045sp2JToyTaaKyXkGejPy']

這與您的[item for item in ids for item in sublist]列表[item for item in ids for item in sublist]的列表理解類似，但是添加了一個測試以查看它是否實際上是我們正在查看的列表。