从python字符串中提取某些单词

Question

I know there are a lot more related questions using regular expressions, but I would like to know what's the best way to extract certain words a from a string and add them to list.

Suppose if my input is of form [A1A B2B, C3C, D4D, E5E], I would like to extract 3rd and 4th word from it. My output should contain list with items ['C3C', 'D4D'] How do i achieve this using the findall?

Note: Every word above is not separated by a comma. There is no comma after A1A and B2B

Answer 1

Using re.findall

s  = "[A1A B2B, C3C, D4D, E5E]"
print (re.findall("\w\d\w",s)[2:4])
'C3C', 'D4D']

Answer 2

Turn the string into a list, (and strip out the , , [ , and ] characters) then slice it:

>>> s = "[A1A B2B, C3C, D4D, E5E]"
>>> l = [val.strip('[,]') for val in s.split()]
>>> l[2:4]
['C3C', 'D4D']

Answer 3

If your input is a list os strings, l = ["A1A B2B", "C3C", "D4D", "E5E"] , then split all the stings in the list into words, and create a new list `l_new' where each element will be one word:

l = ["A1A B2B", "C3C", "D4D", "E5E"]
l_new = sum([x.split() for x in l],[])
l_new[2:4]

Or, if your actual input is a string l = '[A1A B2B, C3C, D4D, E5E]' , then use regular expressions. Remove square brackets and comas, and then split:

import re
l_new = re.split(' ',re.sub('[\[\],]','',l))
l_new[2:4]

Answer 4

Remove the brackets on both sides, split, remove commas, take the slice you want.

mystr = "[A1A B2B, C3C, D4D, E5E]"
mystr = mystr[1:-1]

thelist = [x.replace(",","") for x in mystr.split()][2:4]

print thelist

Answer 5

Searching for words in your input doesn't sound like something that requires a regular expression (searching for values of a given structure does though- so you may want to clarify your input). You would want to use a regular expression though to help you out since you're processing a lot of possible delimiters rather than just a space or comma.

>>> import re
>>> input = "A1A B2B, C3C, D4D, E5E"
>>> input_list = re.findall(r"[\w']+", input)
>>> input_list
['A1A', 'B2B', 'C3C', 'D4D', 'E5E']

Then, given a list of words you're searching for, you can use set intersections to quickly pull out what you need:

>>> search_terms = ['C3C', 'D4D']
>>> list(set(input_list) and set(search_terms))
['C3C', 'D4D']

If you're looking only for words in specific place, use splices (I'm confused about which you need, though, from your question):

>>> input_list[2:4]
['C3C', 'D4D']

If you're searching for specific patterns/values though that would fit a regex, then you need to give us your input and the patterns you want to find so that we can help out with that.