INTRO O

PROBLEM SOLVING AND

PROGRAMMING IN PYTHON

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Prof. Andrea Gallegati
tuj81353@temple.edu

Prof. Dario Abbondanza
tuk96119@temple.edu

CIS 1051 - INTRODUCTION TO CLASSES

Python types

We have already seen different python types

# an integer number
a = 30

# a floating point number
b = 10.

# a string
text = "Hello world"

# a function definition
def print_data(data):
	print(data)
    print(type(data))
    

# Let's print the data 
# we just defined
print_data(a)
print_data(b)
print_data(text)

What if we want to define our custom type (object)

Python classes!

By using

class myObject:
    # a minimal Class
    # without attributes 
    pass

Minimal definition of a class

MyObject

Still a proper class

Python classes!

By using

class Person:
    # Class attribute 
    # (shared by all instances)
    species = "Homo Sapiens"

    def __init__(self, name, age):
        # Instance attributes 
        # (specific to each instance)
        self.name = name
        self.age = age

We can add attributes and methods to a class

This class represents a custom Person object

Python classes!

More about

class Person:
    # Class attribute 
    # (shared by all instances)
    species = "Homo Sapiens"

    def __init__(self, name, age):
        # Instance attributes 
        # (specific to each instance)
        self.name = name
        self.age = age
    
    def info(self):
      	# method (function) to print
      	# info related to our object
      	print(f"{self.name} is {self.age} years old")

Functions inside classes are called methods and can use the attributes defined within the class

Indentation is fundamental!

The __init__ method initializes the object based on the arguments passed

Create a simple class in a module
Instantiate some objects of that class
Perform some operations
Methods can also take as input other objects

Hands-on

Let's do the following together

Create a new class representing something you like
Add a few attributes to be initialized in the constructor
Add a print_info method
Add a method to change an attribute of the instance
Add a method that performs some calculations on numeric attributes and displays the result
Create a main where you instantiate some objects of the newly defined class, and show the use of all the methods implemented

Assignment

python Classes

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