Manav Goyal

Oops - Python

  • Methods
    • Procedural programming
    • Object-oriented programming
  • Class
    • Syntax
          class ClassName:
        # Constructor
        def __init__(self, value):
            self.varName = value
        def functionName(self):
            print(self.varName)
    • Constructor
          class ClassName:
        # Constructor
        def __init__(self, value):
            self.varName = value
        # Alternative Constructor
        @classmethod
        def functionName(cls, varS):
            return cls(varS.split("")[N])
    varName = ClassName("value")
    varName = ClassName.functionName("value")
  • Object
    • Syntax
          varName1 = ClassName(parameters)
    varName1.functionName()
    ClassName.functionName(varName1) # Converted to this above line
    print(varName1.varName)
    print(varName1.__dir__()) # Returns list of all methods that can be used
    print(varName1.__dict__) # Returns dictionary representation of object attributes
    print(help(varName1)) # Returns documentation for an object
    • Instance & Class Variables
          class ClassName:
        varName2 = value2 # Class Variable, Associated with Class
        def __init__(self, value):
            self.varName = value
            self.varName1 = value1 # Instance Variable, Associated with Object
        @classmethod
        def functionName(cls, value):
            cls.varName2 = value # Changes class variable, First argument is instance of Class instead of Object
    varName = ClassName()
    varName.varName1 = value # Changing Instance variable
    varName.varName2 = value # Changing Class variable, Creates a instance variable
    varName.functionName(value) # Changing Class variable
    print(varName.varName2) # First searched for Instance Variable then Class Variable
  • Encapsulation
        class ClassName:
        # Getter
        @property
        def value(self):
            return self._value
        # Setter
        @value.setter
        def __init__(self, value):
            self._value = value
    varName = ClassName(parameters)
    print(varName.value)
  • Inheritance
    • Syntax
          class ClassName:
        # Parent Class
    class ClassName1(ClassName):
        # Child Class
    varName1 = ClassName1()
    • Types
      • Single
      • Multiple
      • Multi-level
      • Hierarchical
      • Hybrid
  • Polymorphism
  • Abstraction
    • Access Modifiers => Just a convention, not actually implemented
          # Public
    class ClassName:
        def __init__(self):
            self.varName = value
        # Private
        def __init__(self):
            self.__varName = value
        # Protected
        def __init__(self):
            self._varName = value
    varName1 = ClassName()
    print(varName1.varName) # Access Public Variable
    print(varName1._ClassName__varName) # Access Private Variable, Name Mangling
    print(varName1._varName) # Access Protected Variable
    • Name Mangling
      • Technique used to protect class private and superclasses private attributes from being accidentally overwritten by subclass
  • Static Method
        # Public
    class ClassName:
        @staticmethod
        def functionName():
            # Statements
    ClassName.functionName(parameters)
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