lecture 02

 

Python variables:

A variable is the name given to a memory location in a program.

->Variables are containers for storing data values.

->Python has no command   for declaring a variable.

->When we create a variable first we have to assign a value to it.

->for example:

 x = 5

y = "bhavana"
print(x)
print(y)

Output:

5

bhavana

Get the type:

If you want get a data type of a variable we use ‘type()’  as a function.

->for example:

           x = 5
y = "bhavana"
print(type(x))
print(type(y))

Output:

<class ‘int’>

<class ‘str’>

Python Datatypes:

Built in Datatypes:

In programming, data type is an important concept.

Variables can store data of different types, and different types can do different things.

Python has the following data types built-in by default, in these categories:

Text Type:	str
Numeric Types:	int, float, complex
Sequence Types:	list, tuple, range
Mapping Type:	dict
Set Types:	set, frozenset
Boolean Type:	bool
Binary Types:	bytes, bytearray, memoryview
None Type:	NoneType

 

Ex:

x = 78
print(type(x))

Output:

<class ‘int’>

Python Numbers:

There are three numeric types in Python:

• int
• float
• complex

Variables of numeric types are created when you assign a value to them:

Ex:

x = 12

y = 9.8

z = 8j

print(type(x))

print(type(y))

print(type(z))

Output:

<class ‘int’>

<class ‘float’>

<class ‘complex’>

Python typecasting:

There may be times when you want to specify a type on to a variable. This can be done with casting. Python is an object-orientated language, and as such it uses classes to define data types, including its primitive types.

Casting in python is therefore done using constructor functions:

• int() - constructs an integer number from an integer literal, a float literal (by removing all decimals), or a string literal (providing the string represents a whole number)
• float() - constructs a float number from an integer literal, a float literal or a string literal (providing the string represents a float or an integer)
• str() - constructs a string from a wide variety of data types, including strings, integer literals and float literals

Ex:

x = int(10)

y = float(2.8)

z = float("3")

w = str(“shiva”)

print(x)

print(y)

print(z)

print(w)

Output:

10

2.8

3

Shiva

Python Strings:

->string is a data type in python.

->string is sequence of characters enclosed in quotes.

Ex:

print("Hello")

print('Bhavana')

Output:

Hello

Bhavana

Assign string to a variable:

Assigning a string to a variable is done with the variable name followed by an equal sign and the string:

Ex:

a = "Avniet"

print(a)

Output:

Avniet

Python Boolean values:

When you compare two values, the expression is evaluated and Python returns true or false.

Ex:1)

print(13> 9)

print(18 == 9)

print(17 < 9)

Output:

True

False

False

2)

a = 280

b = 63

if b > a:

  print("b is greater than a")

else:

  print("b is not greater than a")

Output:

b is not greater than a