Checking string for various (different) patterns

Question

I have a function that will do various regex-matches to find out which courier belongs to the provided tracking-id.

Right now, I'm using many elif statements which works fine but I got the feeling that this isn't very scalable in terms of maintanance.

import re


def get_courier(tracking_id):
    """ Retrieves the courier from a given tracking-id """

    if re.match(r'^ABC\d*$', f'{tracking_id}'):
        courier = "Courier 1"
    elif re.match(r'^\d*-\d$', f'{tracking_id}'):
        courier = "Courier 2"
    elif re.match(r'^PREF\d*$', f'{tracking_id}'):
        courier = "Courier 3"
    # ...
    else:
        courier = None

    return courier

Would there be a possibility to maybe "outsource" the patterns into a file or database where I can define the patterns and their related courier?

I can't get my head around a solution that could work like this

import re


def get_courier(tracking_id):
    """ Retrieves the courier from a given tracking-id """

    patterns = database_select_function()

    courier = re.match(patterns, tracking_id)

    return courier

tracking_id will be an (alphanumeric) string like ABC123456 or 123-456 — Razorfen
– Razorfen, Commented Jan 8, 2021 at 11:30

Stefano Fiorucci - anakin87 · Accepted Answer · 2021-01-08 11:37:09Z

1

A simple better solution for regex pattern matching in python is the following:

import re

courier_patterns={r'^ABC\d*$': 'Courier 1',
                  r'^\d*-\d$': 'Courier 2',
                  r'^PREF\d*$': 'Courier 3'}

def get_courier(tracking_id):
    """ Retrieves the courier from a given tracking-id """

    courier=None

    for pattern, courier_name in courier_patterns.items():
        if re.match(pattern):
            courier=courier_name
            break

    return courier

As you can see, I'm not loading courier patterns from file or DB, but adapting this solution is simple.

answered Jan 8, 2021 at 11:37

Stefano Fiorucci - anakin87

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3 Comments

Tibebes. M Over a year ago

would have been nicer should you extract the matching logic into a separate more generic function (that possibly accepts the set of patterns and the string)

Stefano Fiorucci - anakin87 Over a year ago

@Tibebes.M Please explain better or give your answer. I'm curious and I want to improve my code.

Razorfen Over a year ago

That's brilliant thanks Stefano! The loop through .items() is exactly what I was missing. The rest will be done relatively easy as you already said! :-)

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