Pythonic way to find any item from a list within a string

Question

The problem is simple enough. I'm writing a function which returns true if the string contains any of the illegal names.

line is a string.

illegal_names is an iterable.

def has_illegal_item(line, illegal_names):
    illegal_items_found = False
    for item in illegal_names:
        if item in line:
            illegal_items_found = True
            break
    return illegal_items_found

So this works fine, but it seems a bit clumsy and long-winded. Can anyone suggest a neater and more pythonic way to write this? Could I use a list comprehension or regex?

Unless you know something about the string or illegal names (eg. whitespace separated tokens) I don't think you can use list comprehension — mtsvetkov
– mtsvetkov, Commented Sep 4, 2012 at 11:04

Fred Foo · Accepted Answer · 2012-09-04 11:04:42Z

6

any(name in line for name in illegal_names)

answered Sep 4, 2012 at 11:04

Fred Foo

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4 Comments

James Bradbury Over a year ago

Perfect! Thanks! I even used the word any in my question's title, so perhaps I should've found this.

DSM Over a year ago

The only caveat about simply using in is that it's a substring test, not a word test: "Robert" in "Sarah Robertson" is True. But that may be what you wanted anyway.

Fred Foo Over a year ago

@DSM: true. It's easy enough to turn it into a baseline word check: any(name in re.findall(r"\w+", line) for name in illegal_name). Word splitting can be an NLP-complete problem, though.

James Bradbury Over a year ago

Thanks DSM, I expected that behaviour and it is what I want. I'm setting the list of illegal names as a constant, so I can add whitespaces manually as required.

Colin O'Coal · Accepted Answer · 2012-09-04 11:20:41Z

1

let's have a look on following sample:

line = "This is my sample line with an illegal item: FOO"
illegal_names = ['FOO', 'BAR']

and you want now to find out whether your line contains one of the illegal names, then you do this with the widespread List Comprehension and a length check:

is_correct = not bool(len([ hit for hit in illegal_names if hit in line ]))
# or
is_correct = len([ hit for hit in illegal_names if hit in line ]) == 0

Pretty easy, short and in relation to other lambda version easy to read and unterstand.

-Colin-

answered Sep 4, 2012 at 11:20

Colin O'Coal

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Comments

Kracekumar · Accepted Answer · 2012-09-04 11:27:59Z

0

I go with @larsmans solution, but there another ways of doing it.

def check_names(line, names):
    #names should be set
    parsed_line = set(line.replace(',', '').split())
    return bool(parsed_line.intersection(names))

This can also be written using lambda

In [57]: x = lambda line, names: bool(set(line.replace(",", "").split()).intersection(names))

In [58]: x("python runs in linux", set(["python"]))
Out[58]: True

lamdba version can be overkill of readability

answered Sep 4, 2012 at 11:27

Kracekumar

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2 Comments

James Bradbury Over a year ago

Ah intersection - interesting, but more complicated.

Kracekumar Over a year ago

@JamesBradbury: not complicated but different way to see the same problem.

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