graphing with matplotlib pyplot bar charts bar chart is type of chart or graph that is used to present different discrete categories of data the data is usually presented vertically although in some cases horizontal bar charts may be used each category is represented by bar whose height (or lengthrepresents the data for that category because it is easy to interpret bar chartsand how each category relates to anotherthey are one of the most commonly used types of chart there are also several different common variations such as grouped bar charts and stacked bar charts the following is an example of typical bar chart five categories of programming languages are presented along the axis while the axis indicates percentage usage each bar then represents the usage percentage associated with each programming language the program used to generate the above figure is given below