Requested runtime (Python 3.7.2) is not available for this stack (heroku-18)

django (2.0) I am trying to upload my django app to heroku but i couldn't because it says requested runtime(python 3.7.2) is not available.

Counting objects: 100% (1725/1725), done.
Delta compression using up to 4 threads
Compressing objects: 100% (1721/1721), done.
Writing objects: 100% (1725/1725), 9.34 MiB | 21.00 KiB/s, done.
Total 1725 (delta 93), reused 0 (delta 0)
remote: Compressing source files... done.
remote: Building source:
remote:
remote: -----> Python app detected
remote:  !     Requested runtime (Python 3.7.2) is not available for this stack (heroku-18).
remote:  !     Aborting.  More info: https://devcenter.heroku.com/articles/python-support
remote:  !     Push rejected, failed to compile Python app.
remote:
remote:  !     Push failed
remote: Verifying deploy...
remote:
remote: !       Push rejected to mubashartech.
remote:
To https://git.heroku.com/mubashartech.git
 ! [remote rejected] master -> master (pre-receive hook declined)
error: failed to push some refs to 'https://git.heroku.com/mubashartech.git'