Indexes and columns

We have already referred to indexes and columns without fully defining them. An index contains references to the rows of a DataFrame. The index of a pandas DataFrame is analogous to the row numbers you might see in a spreadsheet. In spreadsheets, it's common to use the so-called A1 notation, where A refers to the columns, which usually begin with A, and 1 refers to the rows, which usually begin with 1.

We will start by looking at the index, and continue with the sample_df_from_lists DataFrame created earlier. You can use the .index method to display information about the index, as follows:

sample_df_from_lists.index

This line of code produces the following output:

RangeIndex(start=0, stop=100, step=1)

You may recall that ranges in Python are inclusive of the start value and exclusive of the end value. You see that the index for sample_df_from_lists runs from 0 to 99, which matches the rows. As you will learn in detail in Chapter 5, Data Selection...