import re

keyword_rx = re.compile('^\$(\w+)\:\s+(\S*)\s*\$$')

# returns tuple (key, value)
# returns None if kwstring is not a keyword expansion
def extract_keyvalue(kwstring):
    mo = keyword_rx.match(kwstring)
    if mo is None: return None

    try:
        return mo.group(1,2)
    except IndexError:
        return None


    
def keywords(*kwstrings):
    keyvalues = [extract_keyvalue(kws) for kws in kwstrings]
    compacted_keyvalues = [kv for kv in keyvalues if kv is not None]
    return dict(compacted_keyvalues)