Adding Prefix To String In A File

Well i have a sort of telephone directory in a .txt file, what i want to do is find all the numbers with this pattern e.g. 829-2234 and append the number 5 to the beginning of the

Solution 1:

You're almost there, but you got your string formatting the wrong way. As you know that 5 will always be in the string (because you're adding it), you do:

word = '5%s' % word

Note that you can also use string concatenation here:

word = '5' + word

Or even use str.format():

word = '5{}'.format(word)

Solution 2:

If you're doing it with regex then use re.sub:

>>>strs = "829-2234   829-1000 111-2234  ">>>regex = re.compile(r"\b(\d{3}-\d{4})\b")>>>regex.sub(r'5\1', strs)
'5829-2234   5829-1000 5111-2234  '