怎么替换字符串特定字符后面的值

现有如下字符串

let str = '?query[form_id]=:form_id&query[type]=form'

改成下方字符串：

str = '?query[form_id]=2027&query[type]=form'

用正则表达式怎么操作？

import re

def refunc(match):
    if match.group(0) == r'\:form_id':
        return '2027'
    else:
        return match.group(0)

s = '?query[form_id]=:form_id&query[type]=form'

result = re.sub(r'\\\:(form_id)', refunc, s)

print(result)