Python Programming | JNTUK | UNIT 1 | Lecture 4

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;

Variables, Assignments,
immutable variables
Numerical types
The concept of data
types

The concept of data types
• A data type consists of a set of values and a set of operations that
can be performed on those values.
• A literal is the way a value of a data type looks to a programmer.

String Literals:
In Python, a string literal is a
sequence of characters
enclosed in single or double
quotation marks.
Empty String
Empty String

String Literals:
quotation marks.
Single Quote inside the String

String Literals:
quotation marks.
Three Quotes for
Multiple line string

String Literals:
quotation marks. n Embedded

Escape Sequences:
• The newline character n is
called an escape sequence.
• Escape sequences are the
way Python expresses
special characters, such as
the tab, the newline, and the
backspace (delete key), as
literals.

String Concatenation:
“Hello” + “world”  Hello
world
a = “welcome”
b = “to”
c = “python”
d = a + b + c  “Welcome to
python”
+ is used for
combining

String Repeating:
“Hi ” * 3  “Hi Hi Hi”
a = “hello ”
b = a*2  “hello hello”
* is used for
combining

if
import
in
is
lambda
nonlocal
with
yield
except
finally
for
from
global
raise
try
while
class
continue
def
del
elif
pass
else
return
and
as
assert
async
await
break
not
or
35
key
words
Started
with
capitals
True
False
None
Variables, Assignments, immutable variables

Variable:
• In Python, a variable is a
reserved memory location
used to store values.
• Python has no command for
declaring a variable. A variable
is created the moment a value
is assigned to it.
• The equal to (=) operator is
used to assign value to a
variable. (Assignment
Operator).
• If we want to store the age of a
person, we should not name
the variable as x, or y or a, or i.
• we should name the variable
as age.

• Use letters
• Use
numbers
with letters
• Use ‘_’ for
long names
a = 5  a variable
A = 6  a variable
(note : A & a are different
variables)
A 1 = 10  a variable
my_name = “Raja”  a
variable

2a = 100  syntax error
a2 = 100  is a variable
if = 5  is a syntax error
If = 5  If is a variable
True = 6  is a syntax error
true = 6  true is a variable
• Don’t start
with
number
• Don’t use
keywords
as variable
names

Multiple Assignment:
• Python allows you to assign a
single value to several
variables simultaneously.
• number1 = number2 = number3 =
100
• This is called chained
assignment.
• We can also assign multiple
objects to multiple variables;
this is called multiple
assignment.
• value1, value2, value3 = 1, 2.5, "Ram“

• Associating a value with a
variable using the assignment
operator (=) is called as
Binding.
Value1 = Value2 =100
Value1 = “Hello”
Print(Value1)  “Hello” not 100
• We cannot use Python variables
without assigning any value.
• If we try to use a variable
without assigning any value
then, Python interpreter shows
error like "name is not defined".

• Most python objects (Booleans,
integers, floats, strings, and tuples)
are immutable.
• This means that after you create the
object and assign some value to it,
you can't modify that value.
• Using the expressions, a = 1 and then
a = 2.
• The object with value 1 still exists in
memory, but you’ve lost the binding
to it. (can’t access it anymore)

Numerical types
Integers:
• This value is represented by int class.
• It contains positive or negative whole
numbers (without fraction or
decimal).
• In Python there is no limit to how
long an integer value can be..
Ex : a = 5, b = 6
type(a)  <class 'int'>
type(b)  <class 'int'>

Numerical types
Float:
• This value is represented by float
class.
• It is a real number with floating point
representation. It is specified by a
decimal point.
• Optionally, the character e or E
followed by a positive or negative
integer may be appended to specify
scientific notation.
Ex : a = 5.5, b = 6.0
type(a)  <class ‘float'>
type(b)  <class ‘float'>

Numerical types
Complex Numbers:
• Complex number is
represented by complex class.
• It is specified as
(real part) + (imaginary part)j.
Ex : a = 2 + 6j, b = - 8 + 2j
type(a)  <class ‘complex'>
type(b)  <class ‘complex'>

Numerical types
Character set:
• All data and instructions in a
program are translated to binary
numbers before being run on a real
computer.
• To support this translation, the
characters in a string each map to an
integer value. This mapping is
defined in character sets, among
them the ASCII set and the
• UNICODE uses between 8 and 32
bits per character, so it can represent
characters from languages from all
around the world.
• ASCII represents lowercase letters (a-
z), uppercase letters (A-Z), digits (0–
9) and symbols

Numerical types
• ASCII Code of Character
“R” is 82
• Row num is 8
• Column num is 2

Numerical types
• Python’s ord and chr functions
convert characters to their
numeric ASCII codes and back
again, respectively.

Boolean types
Boolean:
• Data type with one of the two
built-in values, True or False.
• Boolean objects that are equal
to True or False.
• Note: True and False with
capital ‘T’ and ‘F’ are valid
Booleans.
Ex : a = True , b = False
type(a)  <class ‘bool'>
type(b)  <class ‘bool’>
Ex : a = “true” b = “false”
type(a)  <class ‘str'>
type(b)  <class ‘str’>

Python Programming | JNTUK | UNIT 1 | Lecture 4

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Python Programming | JNTUK | UNIT 1 | Lecture 4