您可以使用

re.sub(r'(?<!\S)(\d{3})-', r'(\1) ', phone)

参见regex demo

• • 详细信息**
• (?<!\S)-左侧空白边界
• (\d{3})-捕获组#1：三位数
• --连字符。

替换为圆括号内的Group 1值和后面的空格（将替换连字符）。

此结果将包括电话格式的检查部分（必须为XXX-XXX-XXXX），如果正确，则re.sub函数将通过：

import re
def convert_phone_number(phone):
  result = re.sub(r'(?<!\S)(\d{3})-(\d{3})-(\d{4}\b)', r'(\1) \2-\3', phone)
  return result

print(convert_phone_number("My number is 212-345-9999.")) # My number is (212) 345-9999.
print(convert_phone_number("Please call 888-555-1234")) # Please call (888) 555-1234
print(convert_phone_number("123-123-12345")) # 123-123-12345
print(convert_phone_number("Phone number of Buckingham Palace is +44 303 123 7300")) # Phone number of Buckingham Palace is +44 303 123 7300

re.sub(r"\b\s(\d{3})-", r" (\1) ", phone)

import re
def convert_phone_number(phone):
  result = re.sub(r"\b\s(\d{3})-\b", r" (\1) ", phone)
  return result

import re
def convert_phone_number(phone):
  result = re.sub(r" (\d{3})-",r" (\1) ",phone)
  return result

使用此：

result = re.sub(r"(\b\d[0-9]{2}\b)-(\b[0-9]{3}\b-\b[0-9]{4}\b)", r"(\1) \2", phone)

result = re.sub(r"(\d{3})-(\d{3})-(\d{4}\b)", r"(\1) \2-\3" , phone)

第一个月

import re
def convert_phone_number(phone):
  result = re.sub(r'(.+)(\d{3})-(\d{3}-\d{4})',r'\1(\2) \3',phone)
  return result
''' the regex searches for  any character with more than 1 occurrence,before the phone format, then the replacement regex formats the string'''
print(convert_phone_number("My number is 212-345-9999.")) # My number is (212) 345-9999.
print(convert_phone_number("Please call 888-555-1234")) # Please call (888) 555-1234
print(convert_phone_number("123-123-12345")) # 123-123-12345
print(convert_phone_number("Phone number of Buckingham Palace is +44 303 123 7300")) # Phone number of Buckingham Palace is +44 303 123 7300