Day 16 Object-Oriented Programming 2

Nov. 10, 2020

Administrative

• Homework 4 is due Fri Nov 13
• Projects Project groups assigned (Email and D2L)
• Midterm is graded. Folks generally did well (91.5% average!).
• No final exam

Project Groups

• Tried to assign you to a group with your first/second choice
• Not possible for everybody, but tried to keep same topical area
• Groups have 3-5 people in them; based on mutual interests
• You will be asked to share the contributions of each member of your group as part of the final project

Pre-Class

• Not too much confusion, more questions of why?
• A couple questions about __str__ vs __repr__

class Point(object):
   def __init__(self,x=0,y=0):
        self.x_coord = x
        self.y_coord = y
   def translate(self,x=0,y=0):
        self.x_coord += x
        self.y_coord += y
   def print_point(self):
        print("({:d},{:d})".format(self.x_coord, self.y_coord))

my_point = Point(1,2)
my_point.print_point()

(1,2)

 class Point(object):
   def __init__(self,x=0,y=0):
        self.x_coord = x
        self.y_coord = y
   def translate(self,x=0,y=0):
        self.x_coord += x
        self.y_coord += y
   def __str__(self):
        return "({:d},{:d})".format(self.x_coord, self.y_coord)

new_point = Point(2,3)
print(new_point)

(2,3)

__str__ vs __repr__

• __str__ finds the informal (human readable) string
• __repr__ find the formal (official) string

import datetime
now = datetime.datetime.now()
str(now)

'2020-11-10 10:31:19.554885'

repr(now)

'datetime.datetime(2020, 11, 10, 10, 31, 19, 554885)'

__str__ vs __repr__

str()	repr()
Make object readable	Required code that reproduces object
Generate output for end user	Generate output for a developer

Questions, Comments, Concerns?