Python Foundation with Data Structures & Algorithms - Part 02
Tags: showdev, python
Published: 2021-08-11 11:05:12

##**Python Variables**

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

The interpreter allocates memory and determines what can be stored in the allocated memory depending on the data type of a variable. As a consequence, you can store integers, decimals, or characters in variables by assigning various data types to them.

Every value in Python has a datatype. Different data types in Python are Numbers, List, Tuple, Strings, Dictionary, etc. Variables in Python can be declared by any name or even alphabets like a, aa, abc, etc.

**Assigning Values to Variables**

     x = 10
     y = "MachineLearning.org.in"
     z = 3.14
     print(x)
     print(y)
     print(z)

10
MachineLearning.org.in
3.14

**Variables do not need to be declared with any particular type, and can even change type after they have been set.**

     x = 10
     x = "MachineLearning.org.in"
     print(x)

MachineLearning.org.in

#####*Multiple Assignment*

     a = b = c = 10
     print(a,b,c)

10 10 10

     a,b,c = 10,3.14,"MachineLearning.org.in"
     print(a)
     print(b)
     print(c)

10
3.14
MachineLearning.org.in


#####*Type Casting*

     x = str(3)  
     print(x)

     y = int(3) 
     print(y)

     z = float(3)
     print(z)

3
3
3.0

#####*Get the Type*

     x = str(3)  
     print(type(x))

     y = int(3) 
     print(type(y))

     z = float(3)
     print(type(z))

<class 'str'>
<class 'int'>
<class 'float'>

     n = input("Enter any value:")
     print(n)
     print(type(n))

Enter any value:Machine Learning
Machine Learning
<class 'str'>

     n = int(input("Enter any value:"))
     print(n)
     print(type(n))

Enter any value:10
10
<class 'int'>

     n = float(input("Enter any value:"))
     print(n)
     print(type(n))

Enter any value:3.14
3.14
<class 'float'>

     n = str(input("Enter any value:"))
     print(n)
     print(type(n))

Enter any value:Machine Learning
Machine Learning
<class 'str'>

#####*Concatenation*

     x = "Learning"
     print("Machine " + x)
 
Machine Learning

     x = "Machine "
     y = "Learning "
     z =  x + y
     print(z)

Machine Learning 

#####*Python has five standard data types −*

Numbers
String
List
Tuple
Dictionary

#####*1. Number*

     a = 10
     print(a)

10

#####*delete number*

     del a

     print(a)

NameError: name 'a' is not defined

#####*2. String*

     s = "MachineLearning.org.in"
     print(s)           # Prints complete string
     print(s[0])        # Prints first character of the string
     print(s[7:15])     # Prints characters starting from 3rd to 5th
     print(s[7:])       # Prints string starting from 3rd character
     print(s * 2)       # Prints string two times
     print('www.' + s)  # Prints concatenated string
     print(s[:])        # Prints complete string with range start to end
     print(s[::])       # Prints complete string with range start to end with increment 1
     print(s[::2])      # Print String with increment of 2
     print(s[-1])       # print last character of a string
     print(s[-3:])      # print last 3 character of a string

MachineLearning.org.in
M
Learning
Learning.org.in
MachineLearning.org.inMachineLearning.org.in
www.MachineLearning.org.in
MachineLearning.org.in
MachineLearning.org.in
Mcieerigogi
n
.in

#####*3. List*

          L = [10,3.14,"Machine",45,'Learning',78.98,69,'.org.in']
          print(L)
          print(L[:])
          print(L[::])
          print(L[0])
          print(L[2:5])
          print(L[2:])
          print(L[:5])
          print(L[-1])
          print(L[-3:])

[10, 3.14, 'Machine', 45, 'Learning', 78.98, 69, '.org.in']
[10, 3.14, 'Machine', 45, 'Learning', 78.98, 69, '.org.in']
[10, 3.14, 'Machine', 45, 'Learning', 78.98, 69, '.org.in']
10
['Machine', 45, 'Learning']
['Machine', 45, 'Learning', 78.98, 69, '.org.in']
[10, 3.14, 'Machine', 45, 'Learning']
.org.in
[78.98, 69, '.org.in']

      L1 = [10,20,30]
      L2 = [40,50,60]
      print(L1 + L2)

[10, 20, 30, 40, 50, 60]

      L1 = [10,20,30]
      print(L1 * 3)

[10, 20, 30, 10, 20, 30, 10, 20, 30]

#####*4. Tuples*

      T = (10,3.14,"Machine",45,'Learning',78.98,69,'.org.in')
      print(T)
      print(T[:])
      print(T[::])
      print(T[0])
      print(T[2:5])
      print(T[2:])
      print(T[:5])
      print(T[-1])
      print(T[-3:])

(10, 3.14, 'Machine', 45, 'Learning', 78.98, 69, '.org.in')
(10, 3.14, 'Machine', 45, 'Learning', 78.98, 69, '.org.in')
(10, 3.14, 'Machine', 45, 'Learning', 78.98, 69, '.org.in')
10
('Machine', 45, 'Learning')
('Machine', 45, 'Learning', 78.98, 69, '.org.in')
(10, 3.14, 'Machine', 45, 'Learning')
.org.in
(78.98, 69, '.org.in')


      T1 = [10,20,30]
      T2 = [40,50,60]
      print(T1 + T2)


[10, 20, 30, 40, 50, 60]


      T1 = [10,20,30]
      print(T1 * 3)

[10, 20, 30, 10, 20, 30, 10, 20, 30]


#####*5. Dictionary*

      d = {}
      print(d)

{}

      d = {'Name':'Kevin','Age':34,'Marks':89.58}
      print(d)
      print(d['Name'])
      print(d['Age'])
      print(d['Marks'])

{'Name': 'Kevin', 'Age': 34, 'Marks': 89.58}
Kevin
34
89.58

      print(d.keys())
      print(d.values())
      print(d.items())

dict_keys(['Name', 'Age', 'Marks'])
dict_values(['Kevin', 34, 89.58])
dict_items([('Name', 'Kevin'), ('Age', 34), ('Marks', 89.58)])