- Create a function that takes arguments
- Create instances of an object from a custom class
- Create a module and import functions into a file
- Explain why design patterns exist and why they're useful
A function is a group of instructions, also known as a named procedure, used by programming languages to return a single result or a set of results.
Functions are a convenient way to divide our code into useful blocks, providing us with order as well as making the code more readable and reusable.
Here is how you define a function in python:
def function_name(input1, input2...):
# 1st block of instructions
# 2nd block of instructions
# ...Let us define a function that returns the square of the input value:
def square(x):
"""Return the square of x.
"""
return x ** 2We can call this function as follows:
length = 7
squared = square(length)
print squareddef rect_area(width, height):
return width * height
width = 10
height = 15
rect = rect_area(width, height)Note: Explain that the mathematical constant
Piis included in themathmodule.
# We are importing the value of pi from
# that module - Easy to read, right?
from math import pi
def circle_area(r):
return pi * r**2
r = 3
area = circle_area(r)
print area10 min
https://gist.github.com/mdang/ba9f9f395a4e6c262f29d94ae37aed18
Pair Exercise 20 min
Starter: https://gist.github.com/mdang/d82ab16ae5129c47a1ea9457b79ebf09
Solution: https://gist.github.com/mdang/fed8c53303dbd479fee4d40dda5a80bf
http://stackoverflow.com/questions/4015417/python-class-inherits-object
@staticmethod keyword
"""Question:
Define a class, which have a class parameter and have a same instance parameter.
Hints:
Define a instance parameter, need add it in __init__ method
You can init a object with construct parameter or set the value later
Solution:
"""
class Person:
# Define the class parameter "name"
name = "Person"
def __init__(self, name = None):
# self.name is the instance parameter
self.name = name
jeffrey = Person("Jeffrey")
print "%s name is %s" % (Person.name, jeffrey.name)
nico = Person()
nico.name = "Nico"
print "%s name is %s" % (Person.name, nico.name)- Polymorphism - Common interface
- Inheritance
- Encapsulation - private, protected, public - hiding implementation details
- Abstraction - Only showing and implementing what is neccessary
- Multiple Inheritance
- Get with the person next to you, discuss why design patterns are useful and some of the different types out there
20 min
"""Define a class named Shape and its subclass Square. The Square class has an init function which takes a length as argument. Both classes have a area function which can print the area of the shape where Shape's area is 0 by default.
Hints:
To override a method in super class, we can define a method with the same name in the super class.
Solution:
"""
class Shape(object):
def __init__(self):
pass
def area(self):
return 0
class Square(Shape):
def __init__(self, l):
Shape.__init__(self)
self.length = l
def area(self):
return self.length*self.length
aSquare= Square(3)
print aSquare.area()"""Define a class named Rectangle which can be constructed by a length and width. The Rectangle class has a method which can compute the area.
Hints:
Use def methodName(self) to define a method.
Solution:
"""
class Rectangle(object):
def __init__(self, l, w):
self.length = l
self.width = w
def area(self):
return self.length*self.width
aRectangle = Rectangle(2,10)
print aRectangle.area()Ref: https://docs.python.org/2/tutorial/modules.html
- the pythonic way for constants is to not grow a class for constants. Just have some const.py with PI = 3.14 and you can import it everywhere. from const import PI
- Create a module with user defined functions. Import them into another file