Not the same as declaring variables, Python do not have to declare the function return type , because of its "if type" language characteristics of the decision. In other languages, such as C / C ++ language prior to storing a data, we need to give this data to open up a fixed memory space in memory, and specify a unique id (variable names) for this type of space, then and only then data to be stored into the memory space for the variable name. The Python approach is `` data-centric, data to be stored up to put into memory, and then go with a variable name `` This reference data.
