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"

• augurar: 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 ['']?
• Alex: I just need to eliminate [''] Thanks

Answer 1

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

• gojomo: I was thinking that, but any() also returns True on a truly empty list.
• sagarchalise: @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.
• gojomo: 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.

Answer 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 == ['']:

Answer 3

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

Answer 4

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.

• James Sapam: what about ls = ['', 1,2,3]

Answer 5

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}}]]

Answer 6

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
>>>

Answer 7

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