Excel Object Model

Objects and Related Concepts

Real-world entities such as flowers, grass, trees, cats, and dogs are called real-world objects. When describing an event using a computer language, it is necessary to first extract the objects related to the event. For example, to describe a cat climbing a tree, we need to extract the two objects: the cat and the tree.

After extracting the objects, we use computer language to write code for description. Their static characteristics or properties are described as attributes, and dynamic characteristics or behaviors are described as methods. For example, when describing a kitten in code, the kitten has attributes such as age, size, color, and breed, and methods such as running, jumping, climbing, and eating. Additionally, an event is the response made by an object when acted upon by a third party. For instance, patting a kitten might make it bite you.

The collection of all code describing these objects is called a class. A class is like a template; once we have it, we can create instances of the class. Just as a master plate for printing banknotes allows us to continuously print banknotes (which are instances of the master plate), an instance is also called an object—it is an abstraction, simulation, emulation, and simplification of a real-world object based on class code. Therefore, we use these simplified code-described objects to replace real-world objects for discussion.

Attributes and methods of an object are collectively called members. They are the interfaces provided by the object to the outside; internal implementation details are encapsulated. When using an object, we mainly use these interfaces. Just like buying a TV, we don’t care about how the circuit boards, transistors, etc., are made inside—we just need to know how to use the external ports.

When using members of an object, we use dot notation. For example, if cat represents a cat object, which has a color attribute (representing color) and a run method (representing the behavior of running), we can use the following way to read the value of the color attribute and assign it to a new variable new_color:

new_color = cat.color

Set the value of the color attribute to 1 (where 1 represents a certain color):

cat.color = 1

Call the run method of the cat object:

cat.run()

Excel Objects and Their Hierarchy

To facilitate script development for users, Excel provides many ready-made objects that have been encapsulated, such as the Application object (representing the Excel application), the Workbook object (representing a workbook), the Worksheet object (representing a worksheet), the Range object (representing a cell range), and the Chart object (representing a chart). They describe and replace real-world scenarios such as office work, files, forms, cell ranges in forms, and actual drawn charts. With these objects, we can use Python to control them programmatically.

The Excel object model shown in Figure 4-1 includes the Application object, Workbook object, Worksheet object, and Range object. They have a subordinate and inclusive relationship from top to bottom—to set an object at the next level, you must first obtain the object at the upper level. Workbooks is a collection containing all Workbook objects in the current Excel application, and the Worksheets collection object contains all Worksheet objects in the current workbook.

Figure 4-1 Excel Object Model