How to add text to the end of a line in a string? - Python

Question

How can I write some text to the end of a line in a multiple-line string in python, without knowing slice numbers? Here's an example:

mystring="""
This is a string.
This is the second Line. #How to append to the end of this line, without slicing?
This is the third line."""

I hope I'm clear.

Answer 1

If the string is relatively small, I'd use str.split('\n') to break it into a list of strings. Then change the string you want, and the join the list:

l = mystr.split('\n')
l[2] += ' extra text'
mystr = '\n'.join(l)

Also, if you can identify uniquely how the line you want to append to ends, you can use replace. For instance, if the line ends with x, then you could do

mystr.replace('x\n', 'x extra extra stuff\n')

Answer 2

First of all, strings are immutable so you will have to build a new string. Use the method splitlines on mystring object (so that you don't have to explicitly specify the line-end char) and then join them into a new string however you wish.

>>> mystring = """
... a
... b
... c"""
>>> print mystring

a
b
c
>>> mystring_lines = mystring.splitlines()
>>> mystring_lines[2] += ' SPAM'
>>> print '\n'.join(mystring_lines)

a
b SPAM
c