clarify 43.7

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/9.0/static/plpython-database.html
Description:

https://www.postgresql.org/docs/9.4/static/plpython-database.html

"If my_table has a column my_column, it would be accessed as:
foo = rv[i]["my_column"]
The number of rows returned can be obtained using the built-in len
function."

It it unclear where 'i' comes from or how it would be used in context.
Also, the 'len' function is mentioned but no example is shown regarding how
to use it. Is there a generic way to access the entire column "my_column" in
foo without using 'i'?

Is the resulting variable 'foo' a list or dictionary?

thanks!