How can I filter items from a list in Python?

Question

I have data naively collected from package dependency lists.

Depends: foo bar baz >= 5.2

I end up with

 d = set([\'foo\',\'bar\',\'baz\',\'         


        

Answer 1

No need for regular expressions here. Use str.isalpha. With and without list comprehensions:

my_list = ['foo','bar','baz','>=','5.2']

# With
only_words = [token for token in my_list if token.isalpha()]

# Without
only_words = filter(str.isalpha, my_list)

Personally I don't think you have to use a list comprehension for everything in Python, but I always get frowny-faced when I suggest map or filter answers.

Answer 2

How about

d = set([item for item in d if re.match("^[a-zA-Z]+$",item)])

that gives you just the values you want, back in d (the order may be different, but that's the price you pay for using sets.