1.13 Variables and Identifiers, Data types

Variables and Identifiers-

A variable is a name that is associated with a value. The assignment operator is used to assign values to variables. An immutable value is a value that cannot be changed.

Num= 10

An identifier is a sequence of one or more characters used to name a given program element. In

Python, an identifier may contain letters and digits, but cannot begin with a digit. The special underscore character can also be used.

Data Types

1.      Integers

2.      Booleans

3.      Floating-Point Types 

Integers

Python integers have unlimited range, subject only to the available virtual memory. This means that it doesn't really matter how big a number you want to store: as long as it can fit in your computer's memory, Python will take care of it. Integer numbers can be positive, negative, and 0 (zero). They support all the basic mathematical operations, as shown in the following example:

>>> a = 12

>>> b = 3

Booleans

There are two built-in Boolean objects: True and False. Like all other Python data types (whether built-in, library, or custom), the bool data type can be called as a function—with no arguments it returns False, with a bool argument it returns a copy of the argument, and with any other argument it attempts to convert the given object to a bool. All the built-in and standard library data types can be converted to produce a Boolean value, and it is easy to provide Boolean conversions for custom data types. Here are a couple of Boolean assignments and a couple of Boolean expressions:

>>> t = True

>>> f = False

>>> t and f

False

>>> t and True

True

Floating-Point Types

Python provides three kinds of floating-point values: the built-in float and complex types, and the decimal. Decimal type from the standard library. All three are immutable. Type float holds double-precision floating-point numbers whose range depends on the C (or C# or Java) compiler Python was built with; they have limited precision and cannot reliably be compared for equality.

Numbers of type float are written with a decimal point, or using exponential notation, for example, 0.0, 4., 5.7, -2.5, -2e9, 8.9e-4.