About Class Book(BaseObject):
This means that you should not instantiate this class yourself . You can call the function xlrd.open_workbook Return this object when
Self instantiation is like this ：
book = Book()
However, this class should not instantiate itself , It's calling xlrd.open_workbook Will return this class
for instance ：
The second code book = xlrd.open_workbook(bookname) It's called xlrd.open_workbook() This function , And then back to a Book object
Then we call xlrd package book.py Inside
Book Functions in class , You can use this second code book To invoke the .
That's it ：
For example, we need to call Book This function in the class
You can use the statement
book.sheet_by_index( 0 ) To call
# here 0 It's a parameter , You can type in
