Python-Multiple conditions under if statement

Question

I am trying to write a function that will classify goods in a given dataset (in a very straightforward way, i know).

It looks like:

def classifier(x):
    if ('smth' or 'smth' or 'smth') in x:
        return 'class1'
    elif ('smth' or 'smth' or 'smth') in x:
        return 'class2'

So, the problem is that some conditions do not work. When I try to check conditions separately - everything works. But in the function something goes wrong.

I use thing function with a pandas apply-method:

data['classes'] = data['subj'].apply(lambda x: classifier(x))

When I try to check conditions separately - everything works. But in the function something goes wrong. can you elaborate? — TZHX
– TZHX, Commented Aug 19, 2019 at 12:30
@TZHX of course, but it will be in Russian... is it okay for you? — nutcracker
– nutcracker, Commented Aug 19, 2019 at 12:31
@nutcracker, пайтон так не работает, ('smth' or 'smth' or 'smth') будет вычислять/сравнивать сами значения по логическому приведению, а не вхождения в список x — RomanPerekhrest
– RomanPerekhrest, Commented Aug 19, 2019 at 12:47
@glglgl, the 1st paragraph in my answer reflects the matter (and elaboration) of those comments. (I've added it after those short comments) — RomanPerekhrest
– RomanPerekhrest, Commented Aug 19, 2019 at 13:28

RomanPerekhrest · Accepted Answer · 2019-08-19 12:53:23Z

5

('smth' or 'smth' or 'smth') performs a consecutive logical comparison left-to-right, but not check for occurrence each of them within a target sequence.

To check if any value from a predefined list (iterable) occurs within a target sequence x use builtin any function:

def classifier(x):
    if any(i in x for i in ('a', 'b', 'c')):
        return 'class1'
    elif any(i in x for i in ('d', 'e', 'f')):
        return 'class2'

edited Aug 19, 2019 at 12:53

answered Aug 19, 2019 at 12:41

RomanPerekhrest

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Comments

Sid · Accepted Answer · 2019-08-19 12:48:30Z

2

You could use this:

def classifier(x):
    if 'smth' in x or 'smth' in x or 'smth' in x:
        return 'class1'
    elif 'smth' in x or 'smth' in x or 'smth' in x:
        return 'class2'

You have to check for each condition separately.

edited Aug 19, 2019 at 12:48

answered Aug 19, 2019 at 12:35

Sid

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4 Comments

nutcracker Over a year ago

is there any difference?

Sid Over a year ago

You have to ask all conditions separately.

nutcracker Over a year ago

why? python-forum.io/…

D. Ben Knoble Over a year ago

@nutcracker that link says it doesnt work (the example that does is a fluke and should not be relied on). ('a' or 'b') is evaulated to produce a string (or possibly boolean) first, which is then used in the membership test. You likely want to know if either is in x, so you need to ask if either is in x.

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