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In this article, you will learn the indexing vs slicing, raw string, list comprehension, 3 types of arguments,Arguments packing & unpacking, How to create constructor, What Are Getters And Setters and Access modifiers.

 

Indexing vs Slicing

What is Indexing?

It creates a reference to an element of an iterable (tuples, strings, list) by its particular position.

How does indexing work?

It searches for a given element in string, list and tuple.

Alphabet = 'abcdefghijklmnopgrstuyxyz'
print (Alphabet [0])
print (Alphabet [-1])
The_list = [1, 2, 3]
The_tuple = (1, 2, 3)
print (The_list [-1])
print (The_tuple[-1])

What is Slicing?

Slicing is a subset of all elements from an iterable (tuples, strings, list) based on their indexes.

  • Closed Ranges - from: to 

text = 'this is python course'
print (text[8:14])
  • open ranges [from:]

text = 'this is python course'
print (text[8:])
  • [to:]

text = 'this is python course'
print (text[:7])
  • [:]

text = 'this is python course'
print (text[:])
  • negative

text = 'this is python course'
print (text[-6:])
  • How do you skip an element in a list?

text = 'abcdefghijklmnopgrstuvwxyz'
print (text[0:7: 2])
  • How do you check if an element in a list ?

text = 'Lorem ipsum dolor sit amet, consectetur adipiscing elit , sed do'
the_list = [1, 2, 2, 3]
the_tuple = (4, 5)
print (text.index('do'))
print (the_list.index(2))
print (the_tuple.index(4))

Note: it takes the first element and ignores the rest.

What is Raw String? 

when you prefix a string with the letter r or R such as r'...' and R'...', that string becomes a raw string. Unlike a regular string, a raw string treats the backslashes (\) as literal characters.

str = '\t python'
file_path = r'c:\xMyfolder\xmysubfolder\xMyfile.txt'
print (file_path)

List Comprehension

It offers a shorter syntax when you want to create a new list based on the values of an existing list.

lst = [ 1, 2, 3, 4]
Multiplied_list = [num * 2 for num in lst ]
print (Multiplied_list)

lst = [ 1, 2, 3, 4, 5]
Multiplied_list = [ num*2 for num in lst if num > 3 ]
print (Multiplied_list)

What Are the Argument Types in Python

Python supports 3 types of arguments:

  1. Positional arguments/ required argument
  2. Default arguments / optional
  3. Keyword Arguments

What is positional/ required argument?

It is an argument that its position matters in a function call.

def info(name, age):
    print('my name is', name,  'and i am', age,  'years old')
info('alaa', 16)

What is Default/ optional arguments?

Python allows function arguments to have default values. If the function is called without the argument, the argument gets its default value.

def info (name = 'alaa', age=16, course='python'):
    print ('my name is ' +name+', I am' , age , 'years old and i am taking '+course+' course.')
info()

def info (name = 'alaa', age=16, course='python'):
    print ('my name is ' +name+', I am' , age , 'years old and i am taking '+course+' course.')
info('alaa salman')

What is Keyword Arguments?

The order of the arguments does not matter.

def info(name, age):

     print ('my name is' , name, 'and i am' , age, 'years old' )

info (age = 16, name = 'alaa' )

Arguments Packing & Unpacking

What is an Arguments Packing?

*args and **kwargs , it’s known as packing, which packs all the arguments in a tuple. If we don’t know the number of arguments to be passed during the function call, we can use packing.

def avg(*args):
    total = sum (args)
    leng = len(args)

    average = total / leng


    print (average)

avg(2, 6, 4)

What is an Arguments UnPacking?

  • During function call, we can unpack python list/tuple and pass it as separate arguments.
  • It  is used for unpacking positional arguments and keyword arguments.

def info (name1, name2, name3):
    print ("first Student's name:" , name1)
    print ("Seconed Student's name:" , name2)
    print ("Third Student's name:", name3)
names = ' Alaa', 'Sara ', 'Amjad '
info(*names)

What is Argument Dictionary Packing?

You can use **kwargs To apply Argument Dictionary Packing.

def info (**kwargs):
    print ('My name is', kwargs['name'])
info(name= 'Alaa', age=17)

What is Argument Dictionary Unpacking?

You can use ** To apply Argument Dictionary UnPacking.

def info (name, age):
    print ('my name is' , name, 'and I am' , age, 'years old')
d= {'name': 'ALI', 'age': 17 }
info(**d)

Creating the constructor in python

The method the __init__() simulates the constructor of the class. This method is called when the class is instantiated. It accepts the self-keyword as a first argument which allows accessing the attributes or method of the class.

class Student:
   def __init__(self, name, age, id, grades):
      self.name = name
      self.age = age
      self.id = id
      self.grades = grades

   def talk(self):
     print ('my name is:' , self.name)

std1 = Student('Alaa', 27, '1234567', 95)
print(std1.name)

What’s Encapsulation?

Encapsulation is a way to ensure security by Getters And Setters Method. Basically, it refers to the bundling of data, along with the methods that operate on that data, into a single unit.

What Are Getters And Setters

  • Getters: These are the methods used in Object-Oriented Programming (OOP) which helps to access the private attributes from a class.

  • Setters: These are the methods used in OOP feature which helps to set the value to private attributes in a class.

class MyInteger:
    def set_val(self, val):
        if (type(val) == int):
            self.val = val
        else:
            print ('the value is not an Integer')
    def get_val(self):
        return self.val
    def increment_val(self):
        self.val+= 1

i = MyInteger()
i.set_val(9)
print (i.get_val())

Access modifiers:

A Class in Python has three types of access modifiers:

  • Public Access Modifier
  • Protected Access Modifier
  • Private Access Modifier

What is public Access Modifier?

The members of a class that are declared public are easily accessible from any part of the program. All data members and member functions of a class are public by default , x=10.

What is protected Access Modifier?

The members of a class that are declared protected are only accessible to a class derived from it. Data members of a class are declared protected by adding a single underscore ‘_’ symbol before the data member of that class , _x=10.

What is private Access Modifier?

The members of a class that are declared private are accessible within the class only, private access modifier is the most secure access modifier. Data members of a class are declared private by adding a double underscore ‘__’ symbol before the data member of that class, __x= 10 .

class Employee:
    def __init__(self,name):
        self.name = name # public
        self._tel = '+966565xxxxxx' #Protected
        self.__salsry = 1700 #Private

emp1 = Employee('Alaa')

print (emp1.name)
print (emp1._tel)
print (emp1.__salary)

Note: By get method, we can access to the private modifier

class Employee:
    def __init__(self,name):
        self.name = name # public
        self._tel = '+966565xxxxxx' #Protected
        self.__salsry = 1700 #Private

    def get_salary(self):
            return self.__salsry

emp1 = Employee('Alaa')

print (emp1.get_salary())
  • How to assign new attributes?

class Student:
    def __init__(self, name, age, id, grades):
        self.name = name
        self.age = age
        self.id = id
        self.grades = grades

        def talk(self):
            print ('My name is:' , self.name)

std1 = Student('Alaa' , 21, 'xx00', [95, 98, 99])
std2 = Student('Reemaz', 19, 'xx01', 86)
std2.v_hours = 16 # assign new attributes 
print (dir(std2))
  • How to delate an attributes?

class Student:
    def __init__(self, name, age, id, grades):
        self.name = name
        self.age = age
        self.id = id
        self.grades = grades

        def talk(self):
            print ('My name is:' , self.name)

std1 = Student('Alaa' , 21, 'xx00', [95, 98, 99])
std2 = Student('Reemaz', 19, 'xx01', 86)
del std2.name
print (dir(std2))
  • How to delate an object?

class Student:
    def __init__(self, name, age, id, grades):
        self.name = name
        self.age = age
        self.id = id
        self.grades = grades

        def talk(self):
            print ('My name is:' , self.name)

std1 = Student('Alaa' , 21, 'xx00', [95, 98, 99])
std2 = Student('Reemaz', 19, 'xx01', 86)

del std2
print (dir(std2))

 

 Conclusion

In this article, It has been discussed the Indexing vs Slicing, Raw String, List comprehension, 3 types of Arguments,Arguments Packing & Unpacking, How to create Constructor, What Are Getters And Setters and Access modifiers.


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