Slightly complex usage of backrefrencing in Python Regular Expressions

Question

Here is my string:

string ='First: Michael, Second: Dennis, Third: Michael, \nAssists: Michael, Scoring: Michael, Rebounds: Peter, Steals: Dennis'

This strings holds many items which represent an accolade and their recipient. I'm attempting to first determine who was the winner of the 'first' accolade, and then pull out all other items involving that recipient.

So in this case, we check who the winner of the first recipient is (Michael), and then we pull out all of the accolades (along with the name Michael) involving Michael.

So the result should be something like:

'First: Michael, Third: Michael, Assists: Michael, Scoring: Michael'

I was trying to utilize back refrencing along with look-arounds, but it got a little messy

import re
string ='First: Michael, Second: Dennis, Third: Michael, \nAssists: Michael, Scoring: Michael, Rebounds: Peter, Steals: Dennis'
re.findall('(?=First: (\w+)), (?=\w+: \w+, )|(\w+: \1,)+', string)

I really think you should split it up into different lines and get the matches that way. — Cory Madden
– Cory Madden, Commented Aug 2, 2017 at 21:19

jsbueno · Accepted Answer · 2017-08-02 21:41:27Z

1

So - this is a nice "puzzle trivia" to do if you want to do it with regexps (and I might even give it a try later) - but all in allyou will have fragile code - it won't work if your input data format change a bit, and it will be a maintenance nightmare.

Now, the "steady" way: pick that string - split it at "," - then split each segment at the ":", strip each component, and create a Python dictionary out of that. Then it is trivial to use a dictionary comprehension expression to extract your desired data:

def get_first_accolade(text):
    parts = text.split(",")
    data = {}
    for item in parts:
         key, value = item.split(",")
         data[key.strip()] = value.strip()
    result = {key: value for key, value in data.items() if value == data["first"]}
    return result

answered Aug 2, 2017 at 21:41

jsbueno

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3 Comments

Cory Madden Over a year ago

This didn't work for me. ValueError: need more than 1 value to unpack

Moondra Over a year ago

I see. I was hoping there was an elegant way to do it with one of RE's group methods.

jsbueno Over a year ago

It probably is possible. It will feel chalenging to get to it, and fun, but I doubt it could be called "elegant" :-)

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