OOAD L8 IntroToPython.pdf - Introduction to Python CSCI...

Introduction to Python
CSCI 4448/5448: Object-Oriented Analysis & Design
Lecture 8
1

Learning Objectives
• Students will be able to…
• Understand why Python is suited to OO designs
• Find support for their own Python language exploration
• Use Python for class projects and future designs
2

Why Python?
• Python: Development Speed
• Python’s syntax emphasizes code readability – estimated that
10% of code required for a given application vs. C
• Built-in memory management
• Python has vast library support for UI and M2M/IoT
communication protocols
• Python’s interactive interpreter allows rapid test of features
while programming
• Python has a complete (?) implementation of object-oriented
design elements
• IEEE 2018 language survey places Python (#1) above C (#4)
[1]
• C++ and Java are #2 and #3
3

• When working in Python, and looking at examples, you will
see the term “Pythonic”
• Pythonic is code that is as simple and readable as possible
• Pythonic code follows the basics of Python code style [4]
• Consider using the pep8 tool to check your code for style
issues [5]
• More information on Python style is available [6]
“Pythonic” Code Style
4

• Beautiful is better than ugly.
• Explicit is better than implicit.
• Simple is better than complex.
• Complex is better than complicated.
• Flat is better than nested.
• Sparse is better than dense.
• Readability counts.
• Special cases aren't special enough to break the rules.
Although practicality beats purity.
• Errors should never pass silently.
• Unless explicitly silenced.
Zen of Python: Tim Peters [7]
5

• In the face of ambiguity, refuse the temptation to guess.
• There should be one-- and preferably only one --obvious way to do it.
• Although that way may not be obvious at first unless you're Dutch*.
• Now is better than never.
• Although never is often better than *right* now.
• If the implementation is hard to explain, it's a bad idea.
• If the implementation is easy to explain, it may be a good idea.
• Namespaces are one honking great idea -- let's do more of those!
• You can see the Zen of Python in a Python interpreter by entering:
• >>> import this
• *Dutch – refers to Guido van Rossum, Python’s creator, who is Dutch.
Zen of Python: Tim Peters [7] continued…
6

• Functional – Direct evaluation of mathematical functions (like
R or Mathematica):
>>> 1+2
3
• Procedural – Structured programs based on modules and
procedure calls (like C):
def add_me(x,y):
print(x+y)
add_me(3,4)
# Output: 7
Python: Functional, Procedural…
7

class MyMath:
input_error = “Bad input”
def error(self):
print(self.input_error)
def adder(x,y,self):
print(x+y)
m = MyMath()
print(m.input_error)
# Output: Bad input
print(m.error())
# Output: Bad input
print(m.adder(3,4))
# Output: 7
Object-oriented – Data
operations via objects with
defined methods; inheritable
classes (like Java and C++):
Python: …and Object-Oriented
8