python:检查任意数量的嵌套列表，以总结是否为空

Question

所以基本上，我试图创建一个函数来检查一个列表，这个列表可能包含许多嵌套的列表，也可能不包含很多嵌套的列表，看看它们是否都是空的。

所以

empty([])将返回true，empty([['']])和empty([[[]]])也将返回true

我试过了

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

但是当我运行这个程序时，会遇到RuntimeError: maximum recursion depth exceeded错误。

有问题的案例字符串是这样的：["[u'3D Blu-ray Disc\\u2122 Player (BD-D7500)']"]，我不知道为什么会导致这个问题

["[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

此函数满足您提供的每个测试用例。

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)']"])

Answer 2

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

我猜..。也许吧

Answer 3

如果0的列表是“空”，Joran的回答肯定是正确的。

如果您只想检查可迭代性，我建议：

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)