# Guided Project: Profitable App Profiles for the App Store

Hello,

I don’t understand in the definition of the function explore_data
print(‘Number of rows:’, len(dataset))
print(‘Number of columns:’, len(dataset[0]))

I understand all the results we get and the function itself but I can’t picture len(dataset) and len(dataset[0]) or the logic behind those two arguments in the dataset itself: how does len (dataset) matches to number of rows or len (dataset[0]) to the number of columns.

2 Likes

Hello @gaelle.c the data set is a list of list, therefore each list is a is a row. To get the total number of rows of the dataset, `len(dataset)` will be used.
since each list in the data set list of list is a row, to get the total number of column in the dataset is well need to calculate the length of any row therefore `len(dataset[0])` is used.

If you have any question feel free to ask me.

The len(dataset) part makes sense now, we did use it previously to get number of rows so I get it. However the len(dataset[0]) is still bugging me. In previous chapters it would have been the row header and cant picture how we get the number of columns from it

1 Like

Great @gaelle.c. since you understood the `len(dataset)` now `len(dataset[0]` will be easy to understand.

`dataset[0]` refers to the first row of the dataset. Every item in this row is a column. Therefore to get the total number of columns we’ll use `len(dataset[0]`.

Is it clear now??

4 Likes

I think it is, thank you

Perfect explanation , I was about to asking the same question too, thank you so much!!

1 Like