Solution 1
Goto File -> Settings
Then
Preferences->Project Interpreter->Python Interpreters

Solution 2
Want have some projects run with Python 2 and some projects running with Python 3 ?
Check under Run > Edit Configurations

Solution 3
In above PyCharm 2019.1+, you can try a new feature called Interpreter in status bar

Enable status bar
You can easily activate pycharm status bar by running the Find Action command (Ctrl+Shift+A
or ⌘+ ⇧+A
on mac). input status bar
and choose View: Status Bar
to see it
