Replace text in multi-line string using text in the same line

Question

Here's a very dummy example of what I'm trying to accomplish, input is text:

{placeholder}, John Jones\n{placeholder}, Ben Franklin\n{placeholder}, George Washington

What I want to do is replace every instance of {placeholder} with the output of a function using data from the same line, e.g. the first initial and last name (would need to input first and last name to a function).

def initializer(name):
    return f"{name.split(' ')[0][0]}. {name.split(' ')[1]}"

The desired result would be:

J. Jones, John Jones\nB. Franklin, Ben Franklin\nG. Washington, George Washington

is your input "{placeholder}, John Jones\n{placeholder}, Ben Franklin\n{placeholder}, George Washington"? or do you have the names in a list? — lmiguelvargasf
– lmiguelvargasf, Commented Sep 24, 2019 at 19:19

Jean-François Fabre · Accepted Answer · 2019-09-24 19:24:01Z

1

A regular expression with a replacement function would work:

import re

s = "{placeholder}, John Jones\n{placeholder}, Ben Franklin\n{placeholder}, George Washington"

def repl_function(m):
    return "{}. {}, {} {}".format(m.group(1)[0],m.group(2),m.group(1),m.group(2))

print(re.sub("\{placeholder},\s+(.*?)\s(.*)",repl_function,s))

prints:

J. Jones, John Jones
B. Franklin, Ben Franklin
G. Washington, George Washington

How does it work?

It captures {placeholder} and 2 words (until end of line, not matched by .* because re.DOTALL is not set and creates 2 groups (2 name parts).

On match, it calls the repl_function replacement function with the match object (second parameter of re.sub can be a string, a bytes object or a function which accepts one argument: the match object).

Just return the reformatted match object as string by shortening the first name and repeating the other information (this can be done in a lambda as well, but it's maybe more readable as a real function)

edited Sep 24, 2019 at 19:24

answered Sep 24, 2019 at 19:23

Jean-François Fabre♦

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1 Comment

TomNash Over a year ago

This is exactly what I was looking for, wasn't sure how to go about using re.sub like this

lmiguelvargasf · Accepted Answer · 2019-09-24 19:30:32Z

1

The following will work assuming you are using Python >= 3.6:

# it is the same function you showed in your question
def initializer(name):
    return f"{name.split(' ')[0][0]}. {name.split(' ')[1]}"

s = '{placeholder}, John Jones\n{placeholder}, Ben Franklin\n{placeholder}, George Washington'
names = [name.rstrip() for name in s.split('{placeholder}, ') if name != '']
output = '\n'.join(f'{initializer(name)}, {name}' for name in names)

Output

'J. Jones, John Jones\nB. Franklin, Ben Franklin\nG. Washington, George Washington'

answered Sep 24, 2019 at 19:30

lmiguelvargasf

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