List Comprehensions and Conditions?

Question

I am trying to see if i can make thsi code more interesting/exciting using list comprehensions. Lets say i have the following lists defined:

a_list = [  'HELLO',
        'FOO',
        'FO1BAR',
        'ROOBAR',
        'SHOEBAR']

regex_list =   [lambda x: re.search(r'FOO', x, re.IGNORECASE),
                lambda x: re.search(r'RO', x, re.IGNORECASE)]

I basically want to add all the elements that do not have any matches in the regex_list into another list.

E.g. ==>

newlist = []

for each in a_list:
    for regex in regex_list:
        if(regex(each) == None):
            newlist.append(each)

How can i do this using list comprehensions? Is it even possible?

Answer 1

Sure, I think this should do it

newlist = [s for s in a_list if not any(r(s) for r in regex_list)]

EDIT: on closer inspection, I notice that your example code actually adds to the new list each string in a_list that doesn't match all the regexes - and what's more, it adds each string once for each regex that it doesn't match. My list comprehension does what I think you meant, which is add only one copy of each string that doesn't match any of the regexes.

Answer 2

I'd work your code down to this:

a_list = ['HELLO',
          'FOO',
          'FO1BAR',
          'ROOBAR',
          'SHOEBAR']
regex_func = lambda x: not re.search(r'(FOO|RO)', x, re.IGNORECASE)

Then you have two options:

1. filter

   newlist = filter(regex_func, a_list)

2. list comprehension

   newlist = [x for x in a_list if regex_func(x)]