Removing list of words and replace

Question

Please Help me on that.

1. I have a list of stopwords and I have a search list. I want to remove those stop words from the search list.
2. After (Step 1), I want to match each split word with Dictionary Values. If Values Match replaces the particular word with corresponding Dictionary Key then join the others words.

So far I have done the Step 1 (see code below). It worked well:

    stopwords=['what','hello','and','at','is','am','i']
    search_list=['where is north and northern side',
                 'ask in the community at western environmental',
                 'my name is alan and i am coming from london southeast']
    dictionary = {'n': ['north','northern'],
                  's': ['south','southern'],
                  'e': ['east','eastern'],
                  'w': ['west','western'],
                  'env': ['environ.','enviornment','environmental']}

    result = [' '.join(w for w in place.split() if w.lower() not in stopwords)
                for place in search_list]

    print (result)

I need the below desirable Final Output to fulfill Step 2. What should I change/include in the above one line of code for getting my desired final output? Any other alternative method also welcome.

['where n n side', 'ask in the community w env', 'my name alan coming from london s']

Answer 1

You have to "reverse" your dictionary, as the lookup is the other way round:

rev_dict = {v:k for k,l in dictionary.items() for v in l}

now it's convenient for a replacement:

>>> rev_dict
{'east': 'e',
 'eastern': 'e',
 'enviornment': 'env',
 'environ.': 'env',
 'environmental': 'env',
 'north': 'n',
 'northern': 'n',
 'south': 's',
 'southern': 's',
 'west': 'w',
 'western': 'w'}

split your string again (you could have kept the list of words as is to avoid the split) and replace with default value as the word, in case of no match:

result = [" ".join([rev_dict.get(x,x) for x in s.split() if x not in stopwords]) for s in search_list]

Or combining both stop words removal and replacements:

stopwords={'what','hello','and','at','is','am','i'}  # define as a set for fast lookup
result = [" ".join([rev_dict.get(x,x) for x in s.split() if x not in stopwords]) for s in search_list]

in both cases, result:

['where n n side', 'ask in the community w env', 'my name alan coming from london southeast']