Branching in git

Suppose you are working on a default branch named 'master' and you want to create a new branch named 'feature'. From 'master', you want to navigate to 'feature' and add a file named 'feature.py$\text{'}$ and commit it$.$ What would be the sequence of commands that you will need to follow in terminal?

$1)$ git add feature.py

$2)$ git checkout $-$b feature

$3)$ git commit $-$m $$feature file added$$

$1,2,3$

$2,1,3$

$3,2,1$

$2,3,1$