1. Engineering Computing
Week 4

2. Object Oriented Programming
Types like int and bool are common and useful in almost every program
Other data types like File are useful, but its not practical for a language to include any and every data type
Programmers can devise their own data type:
Programmers devise classes
They can then create instances of that class called objects

3. Classes A class is similar to a species of animal
Every class has a name
Every class has certain attributes
Properties and values that are important to that class
Every class has methods
Certain functions and blocks of code that the class knows how to execute

4. Example Class
class Model(object): def __init__(self, NAME= ‘Zoolander): self.name = NAME def turnLeft(self): print "I cant turn left" def say(self,string): print string
Constructor-
The code executed to construct a new object
Methods
The different functions each object knows how to execute

5. How to use a class
class Model(object):
def __init__(self, NAME= ‘model’):
self.name = NAME
def turnLeft(self):
print "I cant turn left"
def say(self,string):
print string
We can instantiate objects of a particular class Every object will have the same type of attributes and will know the same functions Because each object is an instance of the class, they will have unique values for their attributes

6. String as Objects Strings are something we call an object
There are lots of things we might want to do with Strings
Capitalization
Reversal
Split
Objects have:
Attributes
Properties of the object
Methods
These are functions that the object knows how to execute that can do something or modify the object
9/18/2018
Lecture 1

7. String objects >>> ‘HITHERE’.lower() ‘hithere’
Method calls from objectives have the following syntax
>>>Object.function(arguments)
Example:
>>> example = ‘Thisisastring’
>>>example.upper()
THISISASTRING
>>> ‘HITHERE’.lower()
‘hithere’
Functions can also take arguments
>>> “This is GREAT”.replace(‘GREAT’,BAD’)
“This is BAD”
9/18/2018
Lecture 1

8. Constructor class DNA(object): def __init__(self,sequence='AT'*5):
if sequence.strip('ATCG') == '':
self.sequence = sequence.upper()
else:
self.sequence = 'ATCG'
print sequence +' is not a valid sequence‘
def __init__(self)
self.sequence = ‘GCTA’

9. Methods
Just like functions, except these functions are specific to handle information and attributes for the object.
Be sure to pass (self) as an argument
def replaceSequence(self,string):
if sequence.strip('ATCG') == '':
self.sequence = string.upper
else:
self.sequence = 'ATCG'
print string +' is not a valid sequence'

10. How to use classes >>>gene1 = DNA()
>>>gene2 = DNA(‘ATAGTA’)
>>>gene1.sequence
‘GCTA’
>>>gene2.sequence
>>>gene2.compliment()
‘TATCAT’
You need to instantiate an object before you can use it
You can access properties with the dot notation
You can access methods in the standard way and pass the appropriate arugments

11. Inheritance
class Chromosome(DNA): def printGeneName(self): print ‘X’ Chromosome inherits all of the methods and properties associated with DNA We can add and specific different methods and attributes