Python- variable+Numbers

Good Morning boys.

Today is the practical class. I hope your practice sessions for Python are continuing at home. Keep the good work going. Today is the day, don't wait.
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By the end of this session, you will be able understand and apply the following concepts:

• What are variable?
• Ways of assigning  variables
• Concepts of multiple assignments
• Introduction to data types in Python (Just introduction)
• Numeric data type - types and exact difference       

_______________________________________________________________________________                                                     PYTHON VARIABLES

Variables are nothing but reserved memory locations to store values. This means that when you create a variable you reserve some space in memory.

Based on the data type of a variable, the interpreter allocates memory and decides what can be stored in the reserved memory. Therefore, by assigning different data types to variables, you can store integers, decimals or characters in these variables.

Assigning Values to Variables

Python variables do not need explicit declaration to reserve memory space. The declaration happens automatically when you assign a value to a variable. The equal sign (=) is used to assign values to variables.

The operand to the left of the = operator is the name of the variable and the operand to the right of the = operator is the value stored in the variable. For example −

(LIVE DEMO- Hyperlink to help you understand the working practically)

Live Demo

#!/usr/bin/python

counter = 100          # An integer assignment
miles   = 1000.0       # A floating point
name    = "John"       # A string

print counter
print miles
print name

Here, 100, 1000.0 and "John" are the values assigned to counter, miles, and name variables, respectively. This produces the following result −

100
1000.0
John

Multiple Assignment

Python allows you to assign a single value to several variables simultaneously. For example −

a = b = c = 1

Here, an integer object is created with the value 1, and all three variables are assigned to the same memory location. You can also assign multiple objects to multiple variables. For example −

a,b,c = 1,2,"john"

Here, two integer objects with values 1 and 2 are assigned to variables a and b respectively, and one string object with the value "john" is assigned to the variable c.
SO, effectively the above SINGLE statement is assigning three variable a,b,c to the following values :
a=1
b=2
c="john"

Standard Data Types

The data stored in memory can be of many types. For example, a person's age is stored as a numeric value and his or her address is stored as alphanumeric characters. Python has various standard data types that are used to define the operations possible on them and the storage method for each of them.

Python has five standard data types −

• Numbers
• String
• List
• Tuple
• Dictionary

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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:

Example

x = 1    # int
y = 2.8  # float
z = 1j   # complex

To verify the type of any object in Python, use the type() function:

Example

print(type(x))
print(type(y))
print(type(z))

Try it Yourself »

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Int

Int, or integer, is a whole number, positive or negative, without decimals, of unlimited length.

Example

Integers:

x = 1
y = 35656222554887711
z = -3255522

print(type(x))
print(type(y))
print(type(z))

Try it Yourself »

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Float

Float, or "floating point number" is a number, positive or negative, containing one or more decimals.

Example

Floats:

x = 1.10
y = 1.0
z = -35.59

print(type(x))
print(type(y))
print(type(z))

Try it Yourself »

Float can also be scientific numbers with an "e" to indicate the power of 10.

Example

Floats:

x = 35e3
y = 12E4
z = -87.7e100

print(type(x))
print(type(y))
print(type(z))

Try it Yourself »

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Complex

Complex numbers are written with a "j" as the imaginary part:

Example

Complex:

x = 3+5j
y = 5j
z = -5j

print(type(x))
print(type(y))
print(type(z))

Try it Yourself »

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Type Conversion

You can convert from one type to another with the int(), float(), and complex() methods. This is also known as TYPECASTING.

Example

Convert from one type to another:

x = 1 # int
y = 2.8 # float
z = 1j # complex
#convert from int to float:a = float(x)

#convert from float to int:b = int(y)

#convert from int to complex:c = complex(x)

print(a)
print(b)
print(c)

print(type(a))
print(type(b))
print(type(c))

Try it Yourself »

Examples

Here are some examples of numbers −

int	long	float	complex
10	51924361L	0.0	3.14j
100	-0x19323L	15.20	45.j
-786	0122L	-21.9	9.322e-36j
080	0xDEFABCECBDAECBFBAEl	32.3+e18	.876j
-0490	535633629843L	-90.	-.6545+0J
-0x260	-052318172735L	-32.54e100	3e+26J
0x69	-4721885298529L	70.2-E12	4.53e-7j

• Python allows you to use a lowercase l with long, but it is recommended that you use only an uppercase L to avoid confusion with the number 1. Python displays long integers with an uppercase L.
• A complex number consists of an ordered pair of real floating-point numbers denoted by x + yj, where x and y are the real numbers and j is the imaginary unit.

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EXERCISE

1. What are variable? Why do we need variables?
2. What can you say about declaration of variable in Python? Give example.
3. In the following statements, 

          a=10.0

          b=57

          c="a"

          d="SCS"

          

           a) what is the data type of the variables a,b,c and d ?

           b) what will be the output of the  statements that follow:

              print(a)

              print(b)

              print(c)

              print(d)        

         4.  What is the purpose of the multiple assignment statements?

          5. What are the numeric data types available? Give example

          6. What is Typecasting? Name the functions used for typecasting.

          7. Give the output of the following set of statements

               a= 27.325

               b=int(a)

               print("b=",b)