🐍 Variables and Objects

Variables, or Data Objects, are named memory spaces holding values.

a = 0
b = 1
type(a)  # int

a, b = b, a  #  Swap
print (a)
print (a,b)
x, y ,z = "Axis-x",  "Axis-y",  "Axis-z"
x = y = z = "Axis"
del a  #  Deletes variables

speed_of_light = 299792458
billionth = 1.0 / 100000000
print(speed_of_light)
nanostick_cm= speed_of_light * billionth * 100
cycles_per_second = 2700000000 #2.7GHz
distance_light_in_cycle= speed_of_light / cycles_per_second
print(distance_light_in_cycle)

message = 'And now for something completely different'

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🦕 Types

A data type is a set of values and a set of operations defined on those values.

type      Set of                    Operators        sample literals
int       Integers                  + - * // % **    99  12  1000
float     Floating Point Numbers    + - * / **       3.14  2.5  1000.00
bool      Boolean Values            and or not       True False
str       Sequences of characters   +                'AB0' "Hello"

🐉 Class

Self-made new types of data. They can contain variables (Properties) and processes (methods).

In Python, all inner values (properties) and processes (methods) are public. Should-be-Restricted elements start with underscore [_]

class class_name:
    #Constructor
def __init__(self, parameters):
        #Code 
    #Properties
    #Methods

---

fname.__doc__ 
>>> doc string

---

class triangle:
  def __init__(self, base, height):
    self.area = area(base,height)
  def area(self, base, height):        
    a= 0.5 * base * hight 
    return a
  def get_area(self, base, height):        
    return self.area

---

class dummy:
    variable = "blah"
    def function(self):        
        print("A message in the class")

---

🦖 Properties & Methods

"Properties" are objects (variables) inside the object. They exist when initialized. Methods are actions subjected to an object.

class MyClass:
    x = 5
    _x = 4  #   "private" 
    def Put(my):
        print(my.x)
#---------
obj = MyClass()  # constructor
print(obj.x)
print(obj._x)   #   it does work 
obj.Put()
del obj.x
del obj

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🐢 Constructor

the constructor init (with two underlines each side)

class User:
  def __init__(self, name, ID, access_level):
    self.name = name
    self.ID = ID
    self.access_level = access_level
  #Method
  def Present(self):
     print(self.name + " reporting for duty.")

User_1 = User("Jane Doe", "007", "Agent")
User_1.Present()

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🐊 Self referencing

The first parameter of a method is the alias to the object itself. The User class can be rewritten as:

class User:
  def __init__(stupid, name, ID, access_level):
    stupid.name = name
    stupid.ID = ID
    stupid.access_level = access_level
  #Method
  def Present(dumb):
     print(dumb.name + " reporting for duty.")

User_1 = User("Jane Doe", "007", "Agent")
User_1.Present()

---

🦎 Inheritance

class Shape:
    def __init__(shape, Sides, Area):
     shape.Sides = Sides
    shape.Area= Area

class Square(Shape):
def __init__(square, l):
 Shape.__init__(    square, 4, l*l)

sq = Square(12)
print (sq.Sides)
print (sq.Area)

🐕‍🦺 IS

The keyword is simply checks whether both variables refer to the same object in memory.

y = x = 3

print(x is y)
# True