Count list/tuple elements which are different than variable?

Question

I have list or/and tuple:

MyVar = [0,0,0,0,1,0,0,0,0]

And I want to count elements in this which are different from 0.

How to do that?

Similar question: https://stackoverflow.com/questions/15375093/python-get-number-of-items-from-listsequence-with-certain-condition — user2314737, Aug 17 '17 at 20:49

score 9 · Answer 1 · answered Aug 17 '17 at 19:57

9

No need to generate lists, just:

len(MyVar) - MyVar.count(0)

answered Aug 17 '17 at 19:57

Grisha S

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AK47 · Answer 2 · 2017-08-17T20:59:47.620

3

Get the length of the sublist of all elements that are not 0

MyVar = [0,0,0,0,1,0,0,0,0]
len([x for x in MyVar if x != 0])
>> 1

edited Aug 17 '17 at 20:59

answered Aug 17 '17 at 19:55

AK47

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Probably not a good idea to use `is` or `is not` to compare values. It's just an implementation detail that `0` is a constant and it's only a constant in CPython. `!=` would be better. – MSeifert Aug 17 '17 at 20:24

o-90 · Answer 3 · 2017-08-17T20:06:35.537

2

You could try:

>>> len(filter(lambda x: x != 0, MyVar))
1

edited Aug 17 '17 at 20:06

answered Aug 17 '17 at 19:53

o-90

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doesn't work in python 3. You don't have to pass an argument to filter. Just pass `None` BTW.: `len(list(filter(None,MyVar)))` – Jean-François Fabre Aug 17 '17 at 20:11
@Jean-FrançoisFabre good thing there isn't a python3 tag on this question :) – o-90 Aug 17 '17 at 20:12
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for me now answers should be python 3 compliant unless otherwise stated. python 2 is history. – Jean-François Fabre Aug 17 '17 at 20:12
@Jean-FrançoisFabre *"...unless otherwise stated"*. As in, how there is specifically a python2.7 tag on this question... – o-90 Aug 17 '17 at 20:15
okay, that was just a comment. The `filter(None,` part is interesting, you should try it, though. – Jean-François Fabre Aug 17 '17 at 20:28

score 2 · Answer 4 · answered Aug 17 '17 at 20:03

2

The following should work:

>>> MyVar = [0,0,0,0,1,0,0,0,0]
>>> sum(map(bool, MyVar))
1

It will convert the list to a list of booleans, with value True iff an element is nonzero. Then it'll sum all elements by implicitly considering True having value 1 and False having value 0.

answered Aug 17 '17 at 20:03

JuniorCompressor

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that for `MyVar = [0,0,0,0,1,0,0,0,3]` will return `1 + 3 = 4` – JuniorCompressor Aug 17 '17 at 20:11
true. OP example isn't representative, as always :) – Jean-François Fabre Aug 17 '17 at 20:12

score 1 · Answer 5 · answered Aug 17 '17 at 19:54

1

Try with filter():

>>> my_var = [0, 0, 0, 0, 1, 0, 0, 0, 0]
>>> result = filter(lambda x: x > 0, my_var)
[1]
>>> print(len(result))
1

answered Aug 17 '17 at 19:54

wencakisa

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MSeifert · Accepted Answer · 2017-08-17T20:34:46.170

1

You could do a sum over a conditional generator expression which doesn't require any intermediate lists or unnecessary arithmetic operations:

>>> sum(1 for element in MyVar if element != 0)
1

or as pointed out by @Jean-François Fabre:

>>> sum(1 for element in MyVar if element)
1

In case the MyVar only contains numbers this counts the number of not-zero values.

edited Aug 17 '17 at 20:34

answered Aug 17 '17 at 20:15

MSeifert

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or `sum(1 for element in MyVar if element)` – Jean-François Fabre Aug 17 '17 at 20:29
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There is a subtle difference between "not zero" and "is truthy" - and the question asked for "not zero". In this case both would give the same result but they wouldn't if the list contains some weird values like empty strings/tuples/dicts/lists. – MSeifert Aug 17 '17 at 20:32

score 0 · Answer 7 · answered Aug 17 '17 at 20:02

0

Not nearly as efficient as any of the answers above, but simple and straight forward nonetheless

myVar = [0,0,0,0,1,0,0,0,0]
count = 0

for var in myVar:
    if var != 0:
        count += 1

answered Aug 17 '17 at 20:02

edm2282

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score 0 · Answer 8 · answered Aug 17 '17 at 20:37

0

With reduce from functools:

from functools import reduce

reduce((lambda x, y: x + (y>0)), MyVar, 0)

answered Aug 17 '17 at 20:37

user2314737

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score 0 · Answer 9 · answered Aug 17 '17 at 20:38

0

f = sum([1 for x in MyVar if x!= 0])

One line :)

answered Aug 17 '17 at 20:38

PYA

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should it be x for x in MyVar? – AK47 Aug 17 '17 at 21:02
2

why? I am doing a sum – PYA Aug 17 '17 at 21:09
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Well it wasn't me that down voted - but I just took a guess at why you received it. – AK47 Aug 17 '17 at 21:12

score 0 · Answer 10 · answered Aug 17 '17 at 20:53

0

Using sum of iterator:

sum(x != 0 for x in MyVar)

answered Aug 17 '17 at 20:53

Jonas Adler

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Count list/tuple elements which are different than variable?

10 Answers10