I wondered what openings I should work on so I wrote this command line application that analyses a collection of chess.com PGNs and counts the wins, losses and draws for both colours. Obviously there's more to chess than the opening, but these statistics give some insight into what to improve in your reportoire.
This program is written in Go and can be installed using:
go get -u github.com/bspaans/chess-archive-collator
Currently this only works for chess.com, as far as I know, as they add an "ECO" code to their tags, which I've used to classify the opening.
Get a month's worth of PGN data:
curl https://api.chess.com/pub/player/bartspaans/games/2019/10/pgn > 2019_10.pgn
Run the program:
chess-archive-collator --player bartspaans 2019_10.pgn
Resulting in something like this (but hopefully with more wins):
Clearly that Sicilian needs some work.
(classifying openings myself is work in progress/might never happen. Incidentally if anyone knows of an open source opening database let me know).