Python breaks each logical line into a sequence of elementary lexical components known as Tokens.

**Tokens**

Python breaks each logical line into a sequence
of elementary lexical components known as **Tokens**.
The normal token types are

1) Identifiers,

2) Keywords,

3) Operators,

4) Delimiters and

5) Literals.

Whitespace separation is necessary between
tokens, identifiers or keywords.

An Identifier is a name used to identify a
variable, function, class, module or object.

·
An identifier must start with an alphabet (A..Z or a..z) or
underscore ( _ ).

·
Identifiers may contain digits (0 .. 9)

·
Python identifiers are case sensitive i.e. uppercase and lowercase
letters are distinct.

·
Identifiers must not be a **python**
keyword.

·
Python does not allow punctuation character such as %,$, @ etc.,
within identifiers.

**Example of valid identifiers**

Sum, total_marks, regno, num1

**Example of invalid identifiers**

12Name, name$, total-mark, continue

**Key**words
are special words used by Python interpreter to recognize the structure of** **program. As these words have specific
meaning for interpreter, they cannot be used for any other purpose.

In computer programming languages operators are
special symbols which represent computations, conditional matching etc. The
value of an operator used is called **operands**.
Operators are categorized as Arithmetic, Relational, Logical, Assignment etc.
Value and variables when used with operator are known as **operands**.

An arithmetic operator is a mathematical
operator that takes two operands and performs a calculation on them. They are
used for simple arithmetic. Most computer languages contain a set of such
operators that can be used within equations to perform different types of
sequential calculations.

Python supports the following Arithmetic
operators.

**Operator - Operation Examples Result **

*Assume a=100 and b=10. Evaluate the following expressions *

+ (Addition) >>>
a + b =110

- (Subtraction) >>>a
– b =90

* (Multiplication) >>> a*b =1000

/ (Divisioin) >>>
a / b =10.0

% (Modulus) >>>
a % 30 =10

** (Exponent) >>>
a ** 2 =10000

// (Floor Division) >>> a//30 (Integer Division) =3

**Program 5.1 To test Arithmetic Operators:**

#Demo Program to test Arithmetic
Operators

a=100

b=10

print ("The Sum= ",a+b)

print ("The Difference =
",a-b)

print ("The Product=
",a*b)

print ("The Quotient = ",a/b)

print ("The Remainder =
",a%30)

print ("The Exponent = ",a**2)

print ("The Floor Division
=",a//30)

#Program End

**Output:**

The Sum= 110

The Difference= 90

The Product= 1000

The Quotient= 10.0

The Remainder= 10

The Exponent= 10000

The Floor Division= 3

A Relational operator is also called as **Comparative** operator which checks the
relationship between two operands. If the relation is true, it returns **True**; otherwise it returns **False**.

Python supports following relational operators

**Coding 5.2 To test Relational Operators:**

#Demo Program to test Relational
Operators

a=int (input("Enter a Value
for A:"))

b=int (input("Enter a Value
for B:"))

print ("A = ",a,"
and B = ",b)

print ("The a==b =
",a==b)

print ("The a > b =
",a>b)

print ("The a < b =
",a<b)

print ("The a >= b =
",a>=b)

print ("The a <= b =
",a<=0)

print ("The a != b =
",a!=b)

#Program End

**Output:**

Enter a Value for A:35

Enter a Value for B:56

A = 35 and B= 56

The a==b= False

The a > b= False

The a < b= True

The a >= b= False

The a <= b= False

The a != b= True

In python, Logical operators are used to
perform logical operations on the given relational expressions. There are three
logical operators they are **and, or**
and **not**.

**Program 5.3 To test Logical Operators:**

**Example – Code**

#Demo Program to test Logical
Operators

a=int (input("Enter a Value
for A:"))

b=int (input("Enter a Value
for B:"))

print ("A = ",a, "
and b = ",b)

print ("The a > b or a ==
b = ",a>b or a==b)

print ("The a > b and a
== b = ",a>b and a==b)

print ("The not a > b =
",not a>b)

#Program End

**Example - Result**

Enter a Value for A:50

Enter a Value for B:40

A = 50 and b = 40

The a > b or a == b = True

The a > b and a == b = False

The not a > b = False

In Python, = is a simple assignment operator to
assign values to variable. Let **a** = 5
and **b **= 10 assigns the value 5 to** a **and 10 to** b **these two assignment statement can also be given** **as **a,b=5,10** that assigns the value 5 and 10 on the right to the
variables a and b respectively. There are various compound operators in Python
like +=, -=, *=, /=, %=, **= and //= are also available.

Ternary operator is also known as conditional
operator that evaluate something based on a condition being true or false. It
simply allows testing a condition in a single line replacing the multiline
if-else making the code compact.

The Syntax conditional operator is,

*Variable Name = [on_true] if [Test expression]
else [on_false]*

**Example :**

min= 50 if 49<50 else 70 # min
= 50

min= 50 if 49>50 else 70 # min
= 70

**Program 5.5 To test Conditional (Ternary) Operator****:**

*#Program to
demonstrate conditional operator *

a, b = 30, 20

*#Copy value of
a in min if a < b else copy b*

min = a if a < b else b

print ("The Minimum of A and
B is ",min)

*# End of the Program*

**Output:**

The Minimum of A and B is 20

Python uses the symbols and symbol combinations
as delimiters in expressions, lists, dictionaries and strings. Following are
the delimiters.

Literal is a raw data given in a variable or
constant. In Python, there are various types of literals.

1. Numeric

2. String

3. Boolean** **

Numeric Literals consists of digits and are
immutable (unchangeable). Numeric literals can belong to 3 different numerical
types Integer, Float and Complex.

**Program 5.6 : To demonstrate Numeric literals**

# Program to demonstrate Numeric
Literals

a = 0b1010 #Binary Literals

b = 100 #Decimal Literal

c = 0o310 #Octal Literal

d = 0x12c #Hexadecimal Literal

print ("Integer Literals
:",a,b,c,d)

*#Float Literal*

float_1 = 10.5

float_2 = 1.5e2

print ("Float Literals
:",float_1,float_2)

*#Complex Literal*

x = 1 + 3.14 j

print ("Complex Literals
:", x)

Print ("x = ", x ,
"Imaginary part of x = ", x.imag, "Real part of x = ",
x.real)

#End of the Program

**Output:**

Integer Literals : 10 100 200 300

Float Literals : 10.5 150.0

Complex Literals :

x = (1.3.14) Imaginary part of x
= 3.14 Real part of 9 *x* = 1.0

In Python a string literal is a sequence of
characters surrounded by quotes. Python supports single, double and triple
quotes for a string. A character literal is a single character surrounded by
single or double quotes. The value with triple-quote "' '" is used to
give multi-line string literal.

**Program 5.7 To test String Literals**

#Demo Program to test String
Literals

strings = "This is
Python"

char = "C"

multiline_str = "'This is a
multiline string with more than one line code."'

print (strings)

print (char)

print (multiline_str)

#End of the Program

**Output:**

This is Python

C

This is a multiline string with
more than one line code.

A Boolean literal can have any of the two
values: True or False.

**Program 5.8 To test Boolean Literals:**

#Demo Program to test String
Literals

boolean_1 = True

boolean_2 = False

print ("Demo Program for
Boolean Literals")

print ("Boolean Value1
:",boolean_1)

print ("Boolean Value2
:",boolean_2)

#End of the Program

**Output:**

Demo Program for Boolean Literals

Boolean Value1 : True

Boolean Value2 : False

In Python strings, the backslash **"\"** is a special character,
also called the **"escape"**
character. It is used in representing certain whitespace characters: **"\t"** is a tab, **"\n"** is a newline, and **"\r"** is a carriage return.
For example to print the message "It's raining", the Python command
is

**>>>print ("It\'Sn
rainning") **

**It's ranning**

Python supports the following escape sequence
characters.

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