Check for strings inside list python

Question

Lets say I have

a = "FIFA 13"

then I writing

"bla" and "13" in a

And result is true... Why? bla is not in the a

If programming was like speaking english, then the amount of bugs in a software would decrease significantly. — Fred
– Fred, Commented Oct 31, 2012 at 21:55
@Fred That's very, very debatable. English is highly ambiguous, an extremely undesirable attribute for programming languages. — NullUserException
– NullUserException, Commented Oct 31, 2012 at 21:56
@Fred - I think the opposite is infinitely more likely. Spoken language, especially English, is far too ambiguous. — g.d.d.c
– g.d.d.c, Commented Oct 31, 2012 at 21:56

inspectorG4dget · Accepted Answer · 2012-10-31 21:59:48Z

8

Your boolean expression is being evaluated as ("bla") and ("13" in a), non-empty strings evaluate as true, so if "13" in a is true then the entire expression will evaluate as true.

Instead, use all():

all(x in a for x in ("bla", "13"))

Or just check both separately:

"bla" in a and "13" in a

edited Oct 31, 2012 at 21:59

inspectorG4dget

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answered Oct 31, 2012 at 21:54

Andrew Clark

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Comments

Roland Smith · Accepted Answer · 2012-10-31 21:55:42Z

3

You should use

In [1]: a = "FIFA 13"

In [2]: "bla" in a and "13" in a
Out[2]: False

answered Oct 31, 2012 at 21:55

Roland Smith

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Comments

Maxime Chéramy · Accepted Answer · 2012-10-31 21:56:44Z

2

"bla" is true

"13" in a is true

Hence, "bla" and "13" in a is true

What you wanted to write is probably : ("bla" in a) and ("13" in a)

answered Oct 31, 2012 at 21:56

Maxime Chéramy

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2 Comments

Roland Smith Over a year ago

You don't need parentheses here. The in operator has a higher precedence than the and operator. See: docs.python.org/2/reference/expressions.html#summary

Maxime Chéramy Over a year ago

I know, it's only for clarity since the person who asked is not familiar with that.

Blender · Accepted Answer · 2012-10-31 21:57:22Z

2

Your code isn't interpreted like it is read:

("bla") and ("13" in a)

"bla" is truthy, so it automatically evaluates to True. "13" in a might be True. False and True evaluates to True, so "bla" isn't really taken into consideration.

You have to be a bit more explicit:

'bla' in a and '13' in a

Or you can use an unreadable one-liner:

all(map(a.__contains__, ('bla', '13')))

For a short-circuiting one-liner, I think you'll have to use itertools.imap instead of map..

answered Oct 31, 2012 at 21:57

Blender

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1 Comment

Ashwini Chaudhary Over a year ago

we can also use operator.contains(), all(map(lambda x:contains(a,x),("bla","12")))

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