Python Programming | JNTUK | UNIT 1 | Lecture 5

UNIT 1 : SYLLABUS
• Conceptual introduction: topics in computer science, algorithms;
• Modern computer systems: hardware architecture, data
representation in computers, software and operating system;
• Installing Python; basic syntax, interactive shell, editing, saving, and
running a script.
• The concept of data types; variables, assignments; immutable
variables; numerical types;
• arithmetic operators and expressions; comments in the program;
understanding error messages;

Expressions
Operators
Error Messages
Comments

ARITHMETIC
BITWISE
MEMBERSHI
P
IDENTITY
LOGICAL
COMPARISION
ASSIGNMENT
Operators

Operators
Arithmetic operators: EXPRESSION RESULT
10 + 20 30
40 - 15 25
15 * 10 150
25 / 5 5.0
5 ** 2 25
15 % 2 1
9 // 2 4
9.0 // 2.0 4.0
-11 // 3 - 4
-11.0 // 3 - 4.0
OPERATOR MEANING
+ Addition
- Subtraction
* Multiplication
/ Division
** Exponent
% Modulus
// Floor Division

Operators
Assignment operators:
• There are two types of assignment
statements in Python. They are:
1. Basic assignment statements
2. Augmented assignment
statements
• The simple syntax for a basic
assignment statement is:
variable_name = expression
• Ex :
a = 2 +3
a = a + 2

Operators
• There are two types of assignment
statements in Python. They are:
1. Basic assignment statements
2. Augmented assignment
statements
• We can combine arithmetic operators
in assignments to form an augmented
assignment statement.
a = a + b is written as a + = b
• Here the left-hand side i.e., a is
evaluated first, then value of b is
evaluated and then addition is
performed, and finally the addition
result is written back to a
x = x * 2 is written as x * = 2

Operators
OPERATOR EXAMPLE SAME AS
= X = 5 X = 5
+= X + = 3 X = X + 3
-+ X - = 3 X = X – 3
*= X * = 3 X = X * 3
/= X / = 3 X = X / 3
%= X % = 3 X = X % 3
//= X //= 3 X = X // 3
**= X ** = 3 X = X ** 3

Operators
Comparison operators:
• Comparison operators are used to
compare two values:
EX:
X = 3, Y = 4, Z = 4
X == Y Output: False
Y == Z Output: True
OPERATOR MEANING EXAMPLE
== Equal X == Y
!= Not Equal X != Y
> Greater than X > Y
< Less Than X < Y
>=
Greater than
or Equal to
X > = Y
<=
Less Than
or Equal to
X < =Y

Operators
Logical operators:
• Logical operators are used to combine conditional statements:
OPERATOR DESCRIPTION EXAMPLE
and
Returns True if both statements are
true
x < 5 and x < 10
or
Returns True if one of the
statements is true
x < 5 or x < 4
not
Reverse the result, returns False if
the result is true
not(x < 5 and x < 10)

Operators
Identity operators:
• Identity operators are used to compare the objects, not if they are equal,
but if they are the same object, with the same memory location:
is
Returns True if both variables are
the same object
x is y
is not
Returns True if both variables are
not the same object
x is not y

Operators
Membership operators:
• Membership operators are used to test if a sequence is presented in an
object:
in
Returns True if a sequence with the
specified value is present in the object
x in y
not in
Returns True if a sequence with the
specified value is not present in the object
x not in y

Operators
Bitwise operators:
• Bitwise operators
are used to compare
(binary) numbers:
OPERATOR MEANING DESCRIPTION
& AND Sets each bit to 1 if both bits are 1
| OR
Sets each bit to 1 if one of two
bits is 1
^ XOR
Sets each bit to 1 if only one of
two bits is 1
- NOT Inverts all the bits
<< Zero fill left shift
Shift left by pushing zeros in from
the right and let the leftmost bits
fall off
>>
Signed right
shift
Shift right by pushing copies of
the leftmost bit in from the left,
and let the rightmost bits fall off

Expressions
• An expression is a combination of
values(Constants), variables and
operators.
• Instructions that a Python
interpreter can execute are called
statements. For example, a = 1 is
an assignment statement.
• a = 10 # This is an assignment
statement
• b = 10 # This is an assignment
statement
• print(a + b)
o # a + b is an expression
o print(a + b) is a statement
• a = b * 5 + c
o # b * 5 + c is an expression
o a = b * 5 + c is a statement

Consider a=1, b=5, c=6, d=3.
Evaluate b – a * c / d + 10 Answer : 13

Comments
• A comment is a piece of program text that
the computer ignores but that provides
useful documentation to programmers.
• # symbol is used to add comments.
a = 10 # a value assigned
b = 20 # b value assigned
c = a + b # sum of a and b assigned to
c

Error Messages
How Python Works:
• In python there are three types of errors;
o Syntax errors
o Semantic errors
o Exceptions

Error Messages
• The most common reason of an error in
a Python program is when a certain
statement is not in accordance with the
prescribed usage. Such an error is called
a syntax error.
• When Python encounters a syntax error
in a program, it halts execution with an
error message.

Error Messages
• A semantic error is detected when the
action that an expression describes
cannot be carried out, even though that
expression is syntactically correct.

Python Programming | JNTUK | UNIT 1 | Lecture 5

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Python Programming | JNTUK | UNIT 1 | Lecture 5