正则表达式中意外的单词边界行为

import re
text = 'washington d.c. columbia'
templ_1 = 'washington d.c'
templ_2 = 'washington d.c.'
print(re.sub(r'\b%s\b'%templ_1, '', text))
import re
text = 'washington d.c. columbia'
tem