Sunny Mittal works on marketing at Data Galactica. Corrections welcome in the comments.

You have three spreadsheets about the same companies. Finance keyed them by Indian CIN, the treasury team by LEI, and the research team pulled theirs from Wikidata, so every row has a Q-id. None of them shares a column you can join on. This post shows a small Python pipeline that (1) validates each identifier locally, so you don't pay to look up typos, and (2) resolves the survivors to one permanent key.

Step 1: know what a valid identifier looks like

Most bad joins start with bad IDs: a trailing space, a lowercase letter, an O where a 0 should be. Each scheme has a structure you can check for free.

Indian CIN (21 characters). Take L85110KA1981PLC013115 :

Part Value Meaning

1 char L Listed ( U = unlisted)

5 digits 85110 Industry code

2 letters KA State of registration

4 digits 1981 Year of incorporation

3 letters PLC Ownership type (e.g.…