Internal of working in Python

This project provides basic and advanced concepts of Python. This project includes all topics of Python Programming such as icontrol statements, Strings, Lists, Tuples, Dictionary, Modules, Exceptions, Date and Time, File I/O, Programs, etc. It has example to Object Oriented programming approach to understand develop applications. It is simple and easy to learn and provides lots of high-level data structures. Also Python interview questions added in this.

Provides the following concepts:

Data Types

Variables can hold values, and every value has a data-type. Python interpreter will automatically interpret variable as an integer type.

Standard data types

A variable can hold different types of values. For example, a person's name must be stored as a string whereas its id must be stored as an integer.

Python provides various standard data types that define the storage method on each of them. The data types defined in Python are given below.

• Numbers
• Integer Its value belongs to int and there is no restriction on the length
• Float Float is used to store floating-point numbers like 1.9, 9.902, 15.2, etc. and the accurate is upto 15 decimal points
• Complex A complex number contains an ordered pair, i.e., x + iy
• ** Sequence Type**
• String The string can be defined as the sequence of characters represented in the quotation marks
• List Lists are enclosed within square brackets [] and it is similar to arrays in C

# Create List 
lst  = [1, "welcome","to" "Python", 2]    
#Checking type of given list  
print(type(lst))
#Printing the lst  
print (lst)
# List slicing
print (lst[3:])
# List slicing  
print (lst[0:2])   
# List Concatenation using + operator  
print (lst + lst)  

• Tuple Tuples are enclosed in parentheses () and contains the collection of the items of different data types. It is read only.

 #Create the tuple  
 _tup  = ("hello", "world", 2)    
 # Checking type of _tup  
 print (type(_tup)) 
 #Printing the tuple  
 print (_tup)
 # Tuple slicing  
 print (_tup[1:])    
 print (_tup[0:1])    

• Dictionary It is enclosed in the curly braces {} and it is an unordered set of a key-value pair of items. Key can hold any primitive data type, whereas value is an arbitrary Python object

  # Creating dictionary with key-value pair of elements 
  d = {1:'C', 2:'C++', 3:'Python', 4:'none'}
  # Printing dictionary
  print (d) 
  # Accesing value using keys  
  print("1st name is "+d[1])   
  print("2nd name is "+ d[4])
  # Printing all Keys and values    
  print (d.keys())    
  print (d.values())    

• Boolean Boolean type provides True and False.

• Set Set is unordered collection of the data type and it is iterable, mutable, and has unique elements.

  # Creating Empty set  
  set1 = set()  
  # Creating set with values 
  set2 = {'1', 2, 3,'Python'} 
  # Adding element to the set
  set2.add(10) 
  # Printing Set value  
  print(set2)
  # Removing element from the set  
  set2.remove(2)  
  print(set2)  

Python operators

The operator can be defined as a symbol which is responsible for a particular operation between two operands. Python provides a variety of operators.

• Arithmetic operators Operators are used to perform arithmetic operations between two operands
• Comparison operators Operators are used to comparing the value of the two operands and returns Boolean true or false accordingly
• ** Assignment operators** Operators are used to assign the value of the right expression to the left operand
• Logical operators Operators are used primarily in the expression evaluation to make a decision
• Bitwise operators Operators perform bit by bit operation on the values of the two operands
• Membership operators Operators are used to check the membership of value inside a Python data structure
• Identity operators Operators are used to decide whether an element certain class or type.(is/is not)

Indentation in Python

In Python, indentation is used to declare a block. If two statements are at the same indentation level, then they are the part of the same block.

Control flow

Decision making allows us to run a particular block of code for a particular decision.

Statement	Description
If Statement	The if statement is used to test a specific condition. If the condition is true, a block of code (if-block) will be executed.
If - else Statement	The if-else statement is similar to if statement except the fact that, it also provides the block of the code for the false case of the condition to be checked. If the condition provided in the if statement is false, then the else statement will be executed.
Nested if Statement	Nested if statements enable us to use if ? else statement inside an outer if statement.

Python Function

A function can be defined as the organized block of reusable code. We can divide a large program into the basic blocks called as function.

There are mainly two types of functions.

• User-define functions - The user-defined functions are those define by the user to perform the specific task.
• Built-in functions - The built-in functions are those functions that are pre-defined in abs(),all(),bin(),

Built-in functions	Description	Example
abs()	return the absolute value of a number	abs(-20)is: 20
all()	accepts an iterable object and returns true if all items are iterable.	k = [1, 3, 4, 6] all(k)is True
bin()	return the binary representation of a integer	bin(10) is: 0b1010
bool()	converts a value to boolean(True or False)	bool(1) is: True ```
bytes()	return the bytes object	bytes("test message", 'utf-8') is: b ' test message'
callable()	eturns true if the object passed appears to be callable, otherwise false.	x = 8 callable(x) is: False
exec()	execution of program (string , object code or large blocks of code	x = 8 exec('print(x==8)') is: True
sum()	to get the sum of numbers of an iterable, i.e., list.	sum([1, 2, 4], 10) is 17
any()	returns true if any item in an iterable is true. Otherwise, it returns False	any([1, 2, 4]) is True
ascii()	returns a string containing a printable representation of an object	ascii('Pythön is interesting' ) is 'Pyth\xf6n is interesting'
bytearray()	returns a bytearray object and can convert objects into bytearray objects, or create an empty bytearray object of the specified size.
eval()	runs python expression(code) within the program	x = 8 eval('x + 1') is 9
float()	returns a floating-point number from a number or string	(float(" -17.19\n") is -17.19
format()	returns a formatted representation of the given value	format(123.0, "d") is 123
frozenset()	returns an immutable frozenset object initialized with elements from the given iterable	frozenset(('m', 'r', 'o', 't', 's')) is frozenset({'o', 'm', 's', 'r', 't'})
getattr()	returns the value of a named attribute of an object
globals()	returns the dictionary of the current global symbol table
lter()	It creates an object which can be iterated one element at a time and return an iterator object	lst = [1,2,3,4,5] lstIter = iter(lst) print(next(lstIter)) is 1
len()	return the length	a = 'Python' ``` print(len(a)) is: 6
list()	creates a list	String = 'python' print(list(String)) is ['p', 'y', 't', 'h', 'o', 'n']
locals()	returns the dictionary of the current local symbol table Symbol table is defined as a data structure which contains all the necessary information about the program. It includes variable names, methods, classes, etc.
memoryview()	returns a memoryview object of the given argument	bin(10) is: 0b1010
map()	return the binary representation of a integer	def calculateAddition(n): return n+n numbers = (1, 2, 3, 4) result = map(calculateAddition, numbers) print(result) is: <map object at 0x7fb04a6bec18>
min()	return the smallest item in an iterable or the smallest of two or more arguments
max()	return the largest item in an iterable or the largest of two or more
next()	retrieve the next item from the iterator
object()	return a new featureless object. object is a base for all classes.	obj = object()
oct()	convert an integer number to an octal string.
open()	open file and return a corresponding file object.
help()	to get help related to the object	f = open("python.txt")
chr()	to get a string representing a character which points to a Unicode code integer	chr(97) is 'a'
complex()	convert numbers or string into a complex number	complex(1,2) is (1.5+2.2j)
delattr()	to delete an attribute from a class
dir()	returns the list of names in the current local scope	print ( dir())
divmod()	to get remainder and quotient of two numbers	divmod(10,2) is (5, 0)
enumerate()	returns an enumerated object	result = enumerate([1,2,3]) print(list(result)) is [(0, 1), (1, 2), (2, 3)]
dict()	creates a dictionary	result = dict(a=1,b=2) `` <br /> print(result) is {'a': 1, 'b': 2}```
filter()	to get filtered elements
hash()	to get the hash value of an object
set()	to create a new set using elements passed	set('12') is {'1', '2'}
hex()	to generate hex value of an integer argument.	hex(1) is 0x1
id()	returns the identity of an object	id("Javatpoint")
setattr()	to set a value to the object's attribute
slice()	to get a slice of elements from the collection of elements	slice(0,5,3) is slice(0, 5, 3)
sorted()	to sort elements	sorted('Python') is ['P', 'y', 't', 'h', 'o', 'n']
input()	to get an input from the user
int()	to get an integer value
isinstance()	to check whether the given object is an instance of that class
ord()	returns an integer representing Unicode code point for the given Unicode character	ord('8')
pow()	to compute the power of a number	pow(4, -2) is 0.0625
print()	prints the given object to the screen or other standard output devices.
range()	returns an immutable sequence of numbers starting from 0 by default, increments by 1 (by default) and ends at a specified number.
reversed()	returns the reversed iterator of the given sequence
round()	rounds off the digits of a number and returns the floating point number	round(6.6) is 7
issubclass()	returns true if object argument(first argument) is a subclass of second class(second argument)
str()	converts a specified value into a string
tuple()	to create a tuple object
type()	returns the type of the specified object if a single argument is passed to the type() built in function

Lambda Functions

A lambda function is a small anonymous function. A lambda function can take any number of arguments.

x = lambda a, b : a * b
print(x(5, 6)) 

Generators

Generators are a special class of functions that simplify the task of writing iterators. Regular functions compute a value and return it, but generators return an iterator that returns a stream of values. Any function containing a yield keyword is a generator function. When you call a generator function, it doesn’t return a single value; instead it returns a generator object that supports the iterator. On executing the yield expression, the generator outputs the value of i, similar to a return statement. The big difference between yield and a return statement is that on reaching a yield the generator’s state of execution is suspended and local variables are preserved. On the next call to the generator’s next() method, the function will resume executing.

def generate_ints(N):
  for i in range(N):
    yield i
 
 gen = generate_ints(3)
 print(next(gen))
 print(next(gen))
 print(next(gen))

0
1
2

Passing values into a generator

simple way to pass values into a generator. yield became an expression, returning a value that can be assigned to a variable or otherwise operated on:

val = (yield i) 

Classes and Objects

class Person:
 def __init__(self, name, age):
   self.name = name
   self.age = age

p1 = Person("John", 36)

init() : function is called automatically every time the class is being used to create a new object self : self parameter is a reference to the current instance of the class, and is used to access variables that belong to the class del : delete the properties of the object or object itself by using the del keyword.

Class

The class can be defined as a collection of objects. It is a logical entity that has some specific attributes and methods.

Object

Everything in Python is an object, and almost everything has attributes and methods.

Method

The method is a function that is associated with an object.

Inheritance

Inheritance is the most important aspect of object-oriented programming. It specifies that the child object acquires all the properties and behaviors of the parent object.

Encapsulation

Encapsulation is also an essential aspect of object-oriented programming. It is used to restrict access to methods and variables. In encapsulation, code and data are wrapped together within a single unit from being modified by accident.

Data Abstraction

Data abstraction and encapsulation both are often used as synonyms.