There are python libraries PyQRCode and qrcode. There are various subscription services with add-ons like tracking, but they are remarkably expensive and so not recommended. If I want fancy tracking of clickthroughs on QR-coded links, I could use bit.ly or some other URL shortener/tracker.
QR codes are additionally supported quietly in lots of software; for example, QR codes are one of the barcode formats supported by DTP package scribus.
Here are some perfectly functional online QR code generators: