How to write a QT program when doing a time consuming task in the background with a progressing bar in the frontend?

JazzTime

Name		Name	Last commit message	Last commit date
Latest commit History 56 Commits
bigdata		bigdata
blog		blog
golang-example		golang-example
jazz_age		jazz_age
monitor		monitor
ocr-qt		ocr-qt
ocr		ocr
opencv-text-recognition		opencv-text-recognition
tDB_Monitor		tDB_Monitor
uniwing_website		uniwing_website
123.jpg		123.jpg
README.md		README.md
blockchain.py		blockchain.py
db.sql		db.sql
feature_extraction.py		feature_extraction.py
feature_matching.py		feature_matching.py
hello.py		hello.py
qt.py		qt.py
reverse_string.py		reverse_string.py
run		run
send_email.py		send_email.py
speech.py		speech.py
webcrawler.py		webcrawler.py
webserver.py		webserver.py