1.2 Dataframes and the ‘dot’ notation

In Week 2 you learned that dataframes have methods, which are like functions, that can only be called in the context of a dataframe.

For example, because the TB deaths dataframe has a column named ‘Country’, the  method can be called like this:

df.sort_values('Country')

Because there is variable name, followed by a dot, followed by the method, this is called dot notation. Methods are said to be a property of a dataframe. In addition to methods, dataframes have another property – attributes.

A multi-coloured image of many different sized circles.
Figure 3

Attributes

A dataframe attribute is like a variable that can only be accessed in the context of a dataframe. One such attribute is which holds a dataframe’s column names.

So the expression  evaluates to the value of the attribute inside the dataframe . The following code will get and display the names of the columns in the dataframe 

df.columns

Index(['Country', 'Population (1000s)', 'TB deaths'],

dtype='object')