Modular Programming

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Modular Programming

• HI5100 Data Structures for BioInformatics
• Lesson 8

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OBJECTIVES

• In this lesson you will learn
• What is a module?
• Why are programs developed using modules?

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Modern Programming

• Complex environments
• Most systems are built using an object-oriented
  (OO) approach
• Before OO programming there was modular
  programming

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Modules

• Code modules organize large amounts of code into
  logical collections of parts that are designed to
  interact in specific ways
• They help programmers reuse code instead of
  rewriting functionality into every program
• Similar in concept to subroutines
• A named section of code designed to complete a
  specific task
• Subroutine is called by name from the main
  program to complete its specific processing task

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Structured Programming

• Before there was modular programming there was
  structured programming
• Eliminate spaghetti code
• Eliminate goto transfer of control
• Main body of code is placed in a subroutine
  called main
• Code to complete specific tasks is placed in the
  program as subroutines with names
• e.g., compute_interest
• Inside main the primary task is handled by
  sequential calls to subroutines with specific
  functionality

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Subroutines

• All modern programming languages provide the
  capability of creating and using subroutines
• Synonyms
• Macros
• Functions
• Lets you write a piece of code that performs a
  specific task
• Can be called frequently from the main program as
  needed

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Advantages of Subroutines

• Code is written once then reused within the
  program
• Main program is more bug-free from the beginning
• Debugging is easier
• Can be used by other programs as well

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Encapsulation

• As long as the inputs and outputs to a subroutine
  remain the same, you can change the internal
  workings of the subroutine all you need to in
  order to make improvements

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Object-Oriented Programming

• Depends on the principle of encapsulation
• And reuse
• And some other principles
• Abstraction
• Polymorphism
• inheritance

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Modular Programming

• Depends on the principle of encapsulation
• And reuse
• And some other principles
• Abstraction

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Modular Programming

• Part of an evolutionary progression for program
  design

Spaghetti Code
Programming
Structured Programming
Modular Programming
Object-Oriented Programming
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Abstraction

• Writing code that is reusable in lots of
  situations
• As opposed to code that is useful in only a
  narrowly defined situation

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Append AAAAAAA
appendAAAAAAA.py def appendAAAAAAA() DNAseq
raw_input(Enter the DNA sequence
to which you want to append AAAAAAA) newDNA
DNAseq AAAAAAA print newDNA

• This program, named appendAAAAAAA.py, gets a DNA
  sequence as input and appends the sequence
  AAAAAAA to it

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Append TTTTT
appendTTTTT.py def appendTTTTT() DNAseq
raw_input(Enter the DNA sequence to
which you want to append TTTTT) newDNA
DNAseq TTTTTT print newDNA

• This program, named appendTTTTT.py, gets a DNA
  sequence as input and appends the sequence TTTTT
  to it

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Append Nucleic Acids
append7.py def append7() DNAseq
raw_input(Enter the DNA sequence to
which you want to append n nucleic
acids of the same type) NAcid
raw_input(Enter the nucleic acid you want to
append by providing its single letter
represenation (A, C, G or T)) howMany
input(Enter the number of nucleic acids of that
type you want to append) newDNA DNAseq
NAcidhowMany print newDNA
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Abstraction

• The task defined as append n nucleic acids of
  the same type
• Usable in several situations
• Is more abstractly defined than the task append
  5 Thymines
• Usable in one narrow situation
• Is more abstractly defined than the task append
  7 Adenines
• Usable in one narrow situation

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Modules and Libraries

• Synonyms
• A module or library collects subroutine
  definitions for use in other programs
• Instead of copying code into each program, just
  point to the file that contains it

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graphics.py Module

• We will gain some experience with Python modules
  by using one that lets us build some GUI elements
  into programs

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graphics.py

• Download graphics.py from our Moodle course site
  or copy and paste the code into a text editor and
  save it as graphics.py in the proper folder
• The proper folder depends on how you did the
  Python install
• It will be something like c\python24\Lib\site-pac
  kages

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Using graphics.py

• GraphWin is a method in the graphics library
• It opens a 200 pixel X 200 pixel window that can
  display graphics
• Try the code below in Pythons interactive mode
• The window created may lie underneath other
  windows you have open
• So you may have to minimize other windows to see
  it

gtgtgtimport graphics gtgtgtwin graphics.GraphWin()
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Window for Graphics
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from import command

• After import graphics we used the GraphWin
  subroutine
• It was called with graphics.GraphWin()
• You can issue a command to import all the
  functions in graphics so that you can call any
  subroutine or function without prefacing the
  function name with graphics.

gtgtgtfrom graphics import gtgtgt win GraphWin()
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Try Out Some Drawing Code

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Sample Drawing Code pg. 1
sampleDraw.py from graphics import def
sampledraw() newwin GraphWin(Plane
Figures) center Point(100,100)
circle1Circle(center,50) circle1.setFill(Green
) circle1.draw(newwin) Label1
Text(center,Hello there!) Label.draw(newwin)
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Sample Drawing Code pg. 2
label1.draw(newwin) for ival in 0,2,4,6
square1 Rectangle(Point(40ival10,20),
Point(100ival10,80))
square1.setFill('Blue')
square1.draw(newwin)
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Sample Drawing Code pg. 3
for ival in 0,2,4,6 square2
Rectangle(Point(140,20ival10),
Point(200,80ival10))
square2.setFill('Red') square2.draw(newwin
)
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sampledraw.py
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Assignment 3

• Search on the World Wide Web for a Python module
  to demo
• Write a short program that demos at least one
  subroutine from the module for me and your fellow
  students
• Provide the program, the module, and whatever
  documentation we need to install the module and
  run your program

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End of Lesson 8