Check for empty list

Question

I have the following output but I want to eliminate the empty lists. How can I do this? It seems that the single quote within the list make it seems like there is something in the list.

[{'Segment': {'Price': 305, 'Mw': 13, '@Number': '1'}}]
[{'Segment': {'Price': 258.43, 'Mw': 46.9, '@Number': '1'}}] 
['']
['']
['']

I tried using the code below but it did not work.

if not a:   
    print "List is empty"

What are the possible list contents? Does each list only contain one item? Are there any other "empty" values you want to eliminate, or just `['']`? — augurar, May 20 '15 at 04:15

score 2 · Answer 1 · edited May 23 '17 at 11:58

2

What you had was a list with a single entry with empty string. It's not an empty list. Best way to check if a list is empty is a correct way to check for empty list.

If you want to check for [''] just do

if a == ['']:

edited May 23 '17 at 11:58

Community

1
1

answered May 20 '15 at 04:09

Nat

3,587
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sagarchalise · Accepted Answer · 2015-05-20T04:22:44.387

2

Your list is not empty, it has one empty string on it. You can use ''.join and check as answered:

if not ''.join(a):
   do your thing

I guess you can use any as well on this if your list is sure to have just empty strings.

if any(a):
    do your thing

edited May 20 '15 at 04:22

answered May 20 '15 at 04:15

sagarchalise

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I was thinking that, but `any()` also returns True on a truly empty list. – gojomo May 20 '15 at 04:17
@gojomo Do you mean `any([])` will be True? I think `all([])` is True and not `any`.The problem I see with any is if the list allows other values as [0] etc where `any` is wrong. – sagarchalise May 20 '15 at 04:20
Yep, never mind, I was still thinking in mode of question, trying to trigger on the 'empty-or-filled-with-empties' condition, and had just tested `all()`. Using `any()` to trigger positive action or `not any()` to trigger the nothing-there handling (like discarding the list) should work. – gojomo May 20 '15 at 04:24

score 0 · Answer 3 · answered May 20 '15 at 04:11

0

if ''.join(out[0]) != "":
    return out

answered May 20 '15 at 04:11

farhawa

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score 0 · Answer 4 · answered May 20 '15 at 04:12

0

Python counts the empty string as a string. Use a regex if you need to, or merely:

if list[0] != '':
    print(list)

Plug that conditional into a For loop as necessary.

answered May 20 '15 at 04:12

manglano

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1

what about ls = ['', 1,2,3] – James Sapam May 20 '15 at 04:14

score 0 · Answer 5 · answered May 20 '15 at 04:17

Is this what you want?

old_list=[[{'Segment': {'Price': 305, 'Mw': 13, '@Number': '1'}}], 
   [{'Segment': {'Price': 258.43, 'Mw': 46.9, '@Number': '1'}}], [''], ['']]

new_list = []

for i in old_list:
    if i != ['']:
        new_list.append(i)

print new_list
[[{'Segment': {'Price': 305, '@Number': '1', 'Mw': 13}}], [{'Segment': {'Price': 258.43, '@Number': '1', 'Mw': 46.9}}]]

score 0 · Answer 6 · answered May 20 '15 at 04:18

Can i try this way:

>>> def is_empty(ls):
...     if all([not len(ls), not ls]):
...         print "List is empty"
...     else:
...         print "List is not empty"
...
>>> is_empty([])
List is empty
>>> is_empty([""])
List is not empty
>>> is_empty([{'Segment': {'Price': 305, 'Mw': 13, '@Number': '1'}}])
List is not empty
>>>

score 0 · Answer 7 · answered May 20 '15 at 04:20

Your list is not empty, it contains an empty string.

If you want to check that your list contains any items that are non-empty you can either use any:

list = [ '' ]
if any(list):
    # List contains non-empty values

or you can filter it before you use it to remove any empty strings:

list = [ '' ]
list = filter(None, list) # Remove empty values from list
if list:
    # List contains items

Check for empty list

7 Answers7