Simple introduction to Python from R

An introduction to objects and object oriented programming in python for users familiar with R.

S3, S4, Reference Classes

class1 = structure(list(string = "ARDKFJSLD"), class = "test")

print.test = function(x) {
  x$string
}

mean.test = function(x) {
  "testtesttest"
}

print(class1)
mean(class1)

S3 and S4 objects have the property that the object itself and the methods for that object are separate.

class2 = setRefClass("test2", 
                      fields = c("string", "number"),
                      methods = list(
                        print = function() {
                          string
                        },
                        
                        getNumber = function() {
                          number
                        }
                      ))
                      
example = class2$new(string = "test", number = 5)
example$print()
example$getNumber()

Classes and Modules in Python

Modules are files which contain python statements. This can contain classes, functions and global variables. Packages are a collection of modules.

#stuff.py
#function:
def cheeseburger():
  print("delicious")
  
#variables:
rabbits = "delicious!"

#classes
class Point:
  """A simple class for a point in 2d space"
  def __init__(self, x, y):
    self.x = x
    self.y = y

Classes have special functions denoted surrounded by __. One such example is the constructor ___init___(). This function will run when the class is initialized.

#example class
class Drugs:
  status = "unknown"
  
  def __init__(self, name, price):
    self.name = name
    self.price = price
  
  def changePrice(self, price):
    self.price = price

This is an example class. Below are two classes that inherit from this class.

class PCP(Drugs):
  status = "illegal"

class Aspirin(Drugs):
  status = "legal"
  
  def isPatented(self):
    return(false)

Alex Shum

Simple introduction to Python from R

S3, S4, Reference Classes

Classes and Modules in Python