A bot that watches two prices so I don't have to

In Argentina, the price of a digital dollar like USDC isn't the same everywhere. Between two P2P markets, where people buy and sell directly with each other, a gap sometimes opens up. Watching it by hand is boring and, by the time you see it, it's gone.

So I built a Python bot that compares prices on p2p.me and Binance P2P every few minutes and sends me a Telegram message only when the gap goes over 1%.

Reading the price at the source

The obvious way to read a price is to open the page and copy it, like a person would. It's slow, needs a login and breaks every time the design changes. On p2p.me the price comes from a public record, so the bot reads it straight from there: no browser and no account. Before trusting that, I checked the number matched what the app shows.

Keep alerts rare

A bot that pings you all the time ends up muted. That's why it only sends a message when the gap goes over a threshold you can adjust. And it can run once and exit, so it can be scheduled to run every few minutes without leaving a computer on all day.

Later I turned the same idea into a page that compares prices across Argentine exchanges.

What I take from it

• —If a piece of data has a public source, read it there and not off the screen. It's faster and doesn't break when a design changes.
• —Before trusting a new source, check it against what the user sees.
• —The bot alerts; it doesn't buy or sell anything. A gap on the screen isn't a profit: fees and delays eat into it.