1.5 Itse1359-1030-variables and identifiers  (Page 5/7)

It also causes a reference to the new object to be stored in the variable named b , replacing the reference to a different object that was previously stored there.

You will be learning a lot more about objects as well as the code visualizer tool in future modules.

Type considerations

In most modern programming systems, values having fractional parts, such as 3.14159 are commonly referred to as floating point types. (This terminology comes from the fact that the decimal point can float back and forthfrom left to right.)

Similarly, whole number values are commonly referred to as integer types. (These are values with no decimal parts, such as, "I have 3 whole apples.")

Advantages and disadvantages

Each type has advantages and disadvantages relative to the other when performing computations.

The range of values

For example, in some systems, the total range of values for a particular integer type is restricted to the set of whole numbers between -32768 and +32767. Anythingoutside that range cannot be handled as a whole number of that integer type.

Although the range of an integer type will be different on different systems, it will almost always be less than the range of a floating point type on thesame system.

Speed

On some systems integer arithmetic is performed much faster than floating point arithmetic. On those systems, if speed is important, usingintegers may be more attractive than using floating point types.

Floating point provides greater range

On most systems, the floating point type provides a much greater range in terms of the values that can be maintained and used for arithmetic. For example,a particular system might be capable of representing the following two values as well as millions of values in between:

• 0.000000000033333
• 333330000000000.0

Sometimes range is important, and sometimes not

Sometimes range is important, and sometimes it isn't. However, as I mentioned above, in some systems this greater range is obtained at some sacrifice inarithmetic speed relative to integer types.

Approximate results

Also, as I will explain in the Review module that goes with this module, floating pointarithmetic often produces approximate results instead of exact results.

While approximate results might be OK for some scientific calculations, they might not be OK for other calculations such as financial calculations for example.

Automatic type handling in Python

In strongly-typed languages such as Java, it is the responsibility of the programmer to make certain that types are handled correctly. For example, itis often not possible to store a floating point value into a variable previously declared to be for the storage of integer values. There is a very strongpossibility that it simply won't fit.

Python takes care of routine type issues automatically

Consider the interactive code fragment shown in Figure 5 . The variables x and y are originally created to store integers and are populated with thevalues 5 and 6 respectively. The variables are added and the correct sum is displayed as output from the interpreter.