How do I interpret this notation?

Question

How and why does the notation s[s] work?

I\'m taking one of the micro-courses from kaggle.com and they use the notation s[s] as shown below. I have not

Answer 1

This is quite complicated.

X_train is a pandas data frame.

X_train.dtypes is returning a pandas Series, where the index (name of each row) is equal to the column name.

We now do == on the Series which returns a new series, with the value true or false. So it looks like:

a True b False c True

Now we get to the x[x] which says to remove the 'false' values, giving a new Series:

a True c True

Now we do .index and turn it into a list to give

['a', 'c' ]