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pythonpython-re

Why do these two regular expressions work differently with re.sub(), but return the same match with re.search()?

Both regex are fetching same match but why does ",([\d-]+)" work as expected and not the "(,\d*-?\d*-?\d*)"? I was expecting both regex to give me same output during re.sub(). What am I missing?

>>> print(re.search(r",([\d-]+)", "Sabrina Green,802-867-5309,System Administrator"))       
<re.Match object; span=(13, 26), match=',802-867-5309'>
>>> print(re.search(r"(,\d*-?\d*-?\d*)", "Sabrina Green,802-867-5309,System Administrator"))       
<re.Match object; span=(13, 26), match=',802-867-5309'>
>>> 
>>> print(re.sub(r",([\d-]+)", r",+1-\1", "Sabrina Green,802-867-5309,System Administrator"))      
Sabrina Green,+1-802-867-5309,System Administrator
>>> print(re.sub(r"(,\d*-?\d*-?\d*)", r",+1-\1", "Sabrina Green,802-867-5309,System Administrator"))
Sabrina Green,+1-,802-867-5309,+1-,System Administrator
>>>

Expected output: Sabrina Green,+1-802-867-5309,System Administrator

Solution

  • You have a typo in your regex string. First, your comma is inside the parethesis, thus ,+1-,802-867-5309

    Second, you should replace the * with + in your regex. Notice the 5309,+1-,System Administrator

    In the future if you're having trouble with regex. You can check out this site. It will break down the regex and give you a visual representation of what you're regex is doing.