Python：如何从列表中删除空列表？
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Python: How to remove empty lists from a list?
提问by SandyBr
I have a list with empty lists in it:
我有一个包含空列表的列表：
list1 = [[], [], [], [], [], 'text', 'text2', [], 'moreText']
How can I remove the empty lists so that I get:
如何删除空列表，以便获得：
list2 = ['text', 'text2', 'moreText']
I tried list.remove('') but that doesn't work.
我试过 list.remove('') 但这不起作用。
采纳答案by Sven Marnach
Try
尝试
list2 = [x for x in list1 if x != []]
If you want to get rid of everything that is "falsy", e.g. empty strings, empty tuples, zeros, you could also use
如果你想摆脱所有“虚假”的东西，例如空字符串、空元组、零，你也可以使用
list2 = [x for x in list1 if x]
回答by Sven Marnach
A few options:
几个选项：
filter(lambda x: len(x) > 0, list1) # Doesn't work with number types
filter(None, list1) # Filters out int(0)
filter(lambda x: x==0 or x, list1) # Retains int(0)
sample session:
示例会话：
Python 2.7.1 (r271:86832, Nov 27 2010, 17:19:03) [MSC v.1500 64 bit (AMD64)] on
win32
Type "help", "copyright", "credits" or "license" for more information.
>>> list1 = [[], [], [], [], [], 'text', 'text2', [], 'moreText']
>>> filter(lambda x: len(x) > 0, list1)
['text', 'text2', 'moreText']
>>> list2 = [[], [], [], [], [], 'text', 'text2', [], 'moreText', 0.5, 1, -1, 0]
>>> filter(lambda x: x==0 or x, list2)
['text', 'text2', 'moreText', 0.5, 1, -1, 0]
>>> filter(None, list2)
['text', 'text2', 'moreText', 0.5, 1, -1]
>>>
回答by user225312
>>> list1 = [[], [], [], [], [], 'text', 'text2', [], 'moreText']
>>> list2 = [e for e in list1 if e]
>>> list2
['text', 'text2', 'moreText']
回答by lunaryorn
You can use filter()instead of a list comprehension:
您可以使用filter()而不是列表理解：
list2 = filter(None, list1)
If Noneis used as first argument to filter(), it filters out every value in the given list, which is Falsein a boolean context. This includes empty lists.
如果None用作 的第一个参数filter()，它将过滤掉给定列表中的每个值，该列表False位于布尔上下文中。这包括空列表。
It might be slightly faster than the list comprehension, because it only executes a single function in Python, the rest is done in C.
它可能比列表推导略快，因为它只在 Python 中执行一个函数，其余的都是在 C 中完成的。
回答by Imran
Calling filterwith Nonewill filter out all falsey values from the list (which an empty list is)
调用filterwithNone将从列表中过滤掉所有假值（空列表是）
list2 = filter(None, list1)
回答by jlandercy
I found this question because I wanted to do the same as the OP. I would like to add the following observation:
我发现这个问题是因为我想做与 OP 相同的事情。我想补充以下意见：
The iterative way (user225312, Sven Marnach):
迭代方式（user225312，Sven Marnach）：
list2 = [x for x in list1 if x]
Will return a listobject in python3and python2. Instead the filter way (lunaryorn, Imran) will differently behave over versions:
将list在python3and 中返回一个对象python2。相反，过滤方式（lunaryorn、Imran）在版本上会有不同的表现：
list2 = filter(None, list1)
It will return a filterobject in python3and a listin python2(see this questionfound at the same time). This is a slight difference but it must be take in account when developing compatible scripts.
它将返回一个filter对象 inpython3和 a listin python2（同时看到这个问题）。这略有不同，但在开发兼容脚本时必须考虑到这一点。
This does not make any assumption about performances of those solutions. Anyway the filter object can be reverted to a list using:
这不会对这些解决方案的性能做出任何假设。无论如何，可以使用以下方法将过滤器对象恢复为列表：
list3 = list(list2)
回答by Arash.H
a = [[1,'aa',3,12,'a','b','c','s'],[],[],[1,'aa',7,80,'d','g','f',''],[9,None,11,12,13,14,15,'k']]
b=[]
for lng in range(len(a)):
if(len(a[lng])>=1):b.append(a[lng])
a=b
print(a)
Output:
输出：
[[1,'aa',3,12,'a','b','c','s'],[1,'aa',7,80,'d','g','f',''],[9,None,11,12,13,14,15,'k']]
回答by SUNITHA K
list1 = [[], [], [], [], [], 'text', 'text2', [], 'moreText']
list2 = []
for item in list1:
if item!=[]:
list2.append(item)
print(list2)
output:
输出：
['text', 'text2', 'moreText']
回答by Chidi
Adding to the answers above, Say you have a list of listsof the form:
添加到上面的答案，假设你有一个list of lists形式：
theList = [['a','b',' '],[''],[''],['d','e','f','g'],['']]
and you want to take out the empty entries from each list as well as the empty lists you can do:
并且您想从每个列表中取出空条目以及您可以执行的空列表：
theList = [x for x in theList if x != ['']] #remove empty lists
for i in range(len(theList)):
theList[i] = list(filter(None, theList[i])) #remove empty entries from the lists
Your new list will look like
你的新列表看起来像
theList = [['a','b'],['d','e','f','g']]
