How to convert 10 digits with this format XXX-XXX-XXXX to US formal format that looks like (XXX) XXX-XXXX using Python3 Regex sub

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This is my try, it actually put the first and seconds groups of 3 digits between parenthesis while I only need to put the first group only between parenthesis to meet US phone number formal format like (XXX) XXX-XXXX. I am asked to do this using re.sub only which means it is a pattern matter and correct syntax which I am missing actually. Thank you very much.

import re 
def convert_phone_number(phone): 
   result = re.sub(r"(\d+-)", r"(\1)", phone) # my actual pattern - change only this line
   return result                              

print(convert_phone_number("My number is 212-345-9999.")) # output should be: My number is (212) 345-9999.
# my actual output: My number is (212-)(345-)9999.
print(convert_phone_number("Please call 888-555-1234")) # output should be: Please call (888) 555-1234
# my actual output: Please call (888-)(555-)1234
python-3.x regex
8 Answers

You may use

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

See regex demo

Details

  • (?<!\S) - a left-hand whitespace boundary
  • (\d{3}) - Capturing group #1: three digits
  • - - a hyphen.

The replacement is the Group 1 value inside round brackets and a space after (that will replace the hyphen).

user_38329700

This result will include the checking part for phone format (it must be XXX-XXX-XXXX), if it correct the re.sub function will pass:

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
user_149893790 
re.sub(r"\b\s(\d{3})-", r" (\1) ", phone)
user_71634680 
import re
def convert_phone_number(phone):
  result = re.sub(r"\b\s(\d{3})-\b", r" (\1) ", phone)
  return result
user_143256170 
import re
def convert_phone_number(phone):
  result = re.sub(r" (\d{3})-",r" (\1) ",phone)
  return result
user_148525500

Use This:

result = re.sub(r"(\b\d[0-9]{2}\b)-(\b[0-9]{3}\b-\b[0-9]{4}\b)", r"(\1) \2", phone)
user_173887810 
result = re.sub(r"(\d{3})-(\d{3})-(\d{4}\b)", r"(\1) \2-\3" , phone)
user_198408590

result = re.sub(r' ([\d]+)-',r' (\1) ',phone)

user_103118720
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