☞The smallest individual unit in a program is known as token.
☞Tokens used in python are : Keywords, Identifiers, Literals, Punctuators, and Operators
☞Identifiers are programmer-defined names given to the various program elements such as variables, functions, objects, classes, lists, dictionaries, etc.
☞Examples of legal identifiers: age, _value, __1_value
☞Examples of illegal identifiers: 123abc, -salary, hello.file
➺It may contain digits, letters and underscore.
➺It must begin with a letter or underscore but not a digit.
➺Python is case sensitive.
☞The data items which never change their value throughout the program run.
☞There are several kinds of literals : Integer literals, Floating or Real literals, Complex literals, String literals, Boolean literals, Special literal [None]
➺They are whole numbers without any fractional part.
➺An integer literal must have at least one digit and must not contain any decimal point.
➺It may contain either + or - sign. A number with no sign is assumed as positive.
➺There are three types of integer literals
➺Numbers which are having the fractional part are referred to as floating literals or real literals.
➺It may be a positive or negative number.
➺A number with no sign is assumed to be a positive number.
➺Example : 2.0, 17.5, -0.00256
➺A real literal in exponent form consists of two parts: mantissa and exponent
➺Example : 0.147 x 108 = 0.147E08
➺Part appearing before E is mantissa and after E is the exponent.
➺It is of the form a + bj, where a and b are floating or real j represents √(-1) which is an imaginary number.
➺a is the real part and b is imaginary
➺It is a sequence of characters surrounded by single or double-quotes.
➺Example : ‘a’, ‘23’, “abc”, “23”, ‘1-h-4j-i’, '''abc''', """abd"""
➺It is True or False.
➺It is used to indicate an absence of value.
➺It is also used to indicate the end of lists in Python.
➺The None value in Python means “There is no useful information” or “There’s nothing here”.
NOTE :- Python can also store literal collections, in the form of tuples and lists, etc.☞Keywords are reserved words that convey a special meaning to the interpreter.
☞There are 33 keywords in Python 3.
☞['False', 'None', 'True', 'and', 'as', 'assert', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'nonlocal', 'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield']
Note : 'False', 'None', 'True' starts with capital letter.☞Punctuators are symbols that are used in programming languages to organize sentence structures, and indicate the rhythm and emphasis of expressions, statements, and program structure.
☞The following characters are used as punctuators:
[ ] | Brackets | These indicates single and multidimensional array subscripts |
() | Parenthesis | These indicate function calls and function parameters. |
{ } | Braces | Indicate the start and end of compound statements. |
; | Semicolon | This is a statement terminator. |
, | Comma | It is used as a separator. |
: | Colon | It indicates a labeled statement |
= | Equal to | It is used as an assigning operator. |
☞An operator is a symbol or character which triggers some operation (computation) on its operands.
☞Types of operators:- Arithmetic Operators, Relational Operators, Logical Operators, Bitwise Operators, Assignment Operators, Identity Operators, Membership Operators