Adding symlink to /usr/bin
/usr/bin is, as a lot of directories installed by default, protected by SIP and can't be modified by any user. There are ways to disable SIP, but the better approach is to use the directories beneath /usr/local for user-installed things

sudo mkdir /usr/local/bin
sudo ln -s /Library/Frameworks/Python.framework/Versions/3.7/bin/python3 /usr/local/bin/
sudo sh -c 'grep -q "/usr/local/bin" /etc/paths || echo "/usr/local/bin" &gt;&gt; /etc/paths'


The last line will make sure that /usr/local/bin is part of PATH for all shells started/Terminal tabs created after the line has been executed.