python：檢查任意數量的嵌套列表以得出是否為空的結論

Question

所以基本上我想創建一個函數來檢查一個列表，該列表可能包含也可能不包含列表的許多嵌套層，以查看它們是否都是空的。

所以

empty([])將返回true，因此empty([['']])和empty([[[]]])

我試過了

def empty(seq):
     try:
         return all(map(empty, seq))
     except TypeError:
         return False

但遇到RuntimeError: maximum recursion depth exceeded我運行此代碼時， RuntimeError: maximum recursion depth exceeded錯誤。

有問題的情況字符串是這樣的： ["[u'3D Blu-ray Disc\\\™ Player (BD-D7500)']"]我不知道為什么這會導致此問題

["[u'3D Blu-ray Disc\\u2122 Player (BD-D7500)']"]
maximum recursion depth exceeded in cmp
Traceback (most recent call last):
  File "./dashboard.py", line 583, in download
    return get_rows_from_db(str(job.id), job.url,taskid, options,trial)
  File "./dashboard.py", line 123, in get_rows_from_db
    print "B " + empty(col)
  File "./dashboard.py", line 52, in empty
    for item in seq)
  File "./dashboard.py", line 52, in <genexpr>
    for item in seq)
  File "./dashboard.py", line 52, in empty
    for item in seq)
  File "./dashboard.py", line 52, in <genexpr>
    for item in seq)
  File "./dashboard.py", line 52, in empty
    for item in seq)
  File "./dashboard.py", line 52, in <genexpr>
    for item in seq)
  File "./dashboard.py", line 52, in empty
    for item in seq)
  File "./dashboard.py", line 52, in <genexpr>
    for item in seq)
  File "./dashboard.py", line 52, in empty
    for item in seq)
  File "./dashboard.py", line 52, in <genexpr>
    for item in seq)
  File "./dashboard.py", line 52, in empty
    for item in seq)
  File "./dashboard.py", line 52, in <genexpr>
    for item in seq)
  File "./dashboard.py", line 52, in empty
    for item in seq)
  File "./dashboard.py", line 52, in <genexpr>
    for item in seq)
  File "./dashboard.py", line 52, in empty
    for item in seq)
  File "./dashboard.py", line 52, in <genexpr>
    for item in seq)
  File "./dashboard.py", line 52, in empty
    for item in seq)
  File "./dashboard.py", line 52, in <genexpr>
    for item in seq)
  File "./dashboard.py", line 52, in empty
    for item in seq)
  File "./dashboard.py", line 52, in <genexpr>
    for item in seq)
  File "/usr/lib/python2.7/abc.py", line 132, in __instancecheck__
    if subclass is not None and subclass in cls._abc_cache:
  File "/usr/lib/python2.7/_weakrefset.py", line 73, in __contains__
    return wr in self.data
RuntimeError: maximum recursion depth exceeded in cmp

Answer 1

def empty(L_or_I):
    if not L_or_I:
       return True
    if isinstance(L_or_I,(list,tuple)):
       return all(empty(x) for x in L_or_I)
    return False

我想...也許

Answer 2

如果列表0為“空”，那么Joran的答案肯定是正確的。

如果您只想檢查可迭代，我建議：

import collections
def empty(e):
    if not isinstance(e, collections.Iterable):
        return False
    if not e:
        return True
    return all(empty(x) for x in e)

Answer 3

此功能滿足您提供的每個測試用例。

import collections


def empty(seq):
    if isinstance(seq, basestring):
        return seq == ''
    return all(empty(item)
               if isinstance(item, collections.Sequence)
               else False
               for item in seq)

assert empty([])
assert empty([['']])
assert empty([[[]]])
assert not empty([[[], 1]])
assert empty(u'')
assert not empty(u'1')
assert not empty(["[[u'3D Blu-ray Disc\\u2122 Player (BD-D7500)']"])