Python --替换字符串中的字串

def extend(format,d,maker='"',safe=True):

    if safe:

        def lookup(w): return d.get(w,w.join(maker*2))

    else:

        def lookup(w): return d[w]

    parts=format.split(maker)

    print parts

    parts[1::2]=map(lookup, parts[1::2])

    print parts

    return ' '.join(parts)

if __name__=='__main__':

    print extend('just "a" test',{'b':'one'})