Transcript Professional Computing - School of Computer Science

TEACHING
PROGRAMMING BY
ITERATIVE DEEPENING
Dr. Mark Lee | [email protected]
School of Computer Science, University of
Birmingham
http://www.cs.bham.ac.uk/~mgl/python/
Some Quotes
• If debugging is the process of removing software bugs,
then programming must be the process of putting them in.
(Edsger Dijkstra)
• Debugging is twice as hard as writing the code in the first
place. Therefore if you write your code as cleverly as
possible then by definition you will be too stupid to debug
it. (Brian Kernighan)
• Logic is useless – when are we going to learn something
useful? Like programming games. (First year CS student
on my course – now departed)
Introduction
Programming is a
• Craft
• Engineering (good or bad)
• The application of Computer Science
In this talk I’ll give
• An overview of Python
• Reasons why it’s an ideal first language for kids (and adults)
But my real message is
• Writing code is about
1.
2.
3.
4.
Recognising/Abstracting a problem
Designing/Recalling a solution (the algorithm)
Implementation (programming)
Debugging & improvement
• Programming cannot be isolated from the rest of computing
New Computing Curriculum 2014
• Computational Thinking:
• Decomposition
• Pattern Recognition
• Abstraction
• Pattern Generalisation
• Algorithm Design
(from Computing in the National Curriculum, CAS 2014)
• From the new Curriculum for KS3
• Understand several key algorithms that reflect computational thinking;
use logical reasoning to compare the utility of different algorithms for
the same problem.
• “Use two or more programming languages, at least one of which is
textual, to solve a variety of computational problems; make use of
appropriate data structures; design and develop modular programmes
that use procedures or functions.”
Python
• Created by Guido Van Rossum in 1991
• General Purpose High Level Programming Language
• Emphasis on readability
• Emphasis on consistency
• Typically succinct compared to other languages (e.g. C,
Java etc.
• Python 3.4.1 (May 2014)
• Dynamic Type system
• Highly extendable
• Typically a procedural language – but support for Object Oriented,
Functional programming styles.
Code Snippets
print (“hello world”)
def shopping () :
shopping_list = ['spam', "eggs", "ham"]
count = 0
for item in shopping_list :
print (item)
count = count + 1
print ("total items is " + str(count))
http://blog.codeeval.com/codeevalblog/2014#.U0JQBedd
V5A=
Python in the real world
More realistically …
Why is Python popular?
• Python cannot compete with
• Speed of C, C++, C# (games programming)
• Specific technology friendliness of Javascript, VB.net, C#, Swift, Ruby on Rails
etc.
• Scalability and portability of Java
• Higher Education Dominance of Java in undergraduate studies
(but)
• Python is
• Fun
• Highly readable
• Quick to learn
• “Good enough” for most jobs
• Easy to debug
• Great community
• Native to Android, Raspberry PI, Linux, Apple IOS
• Good stepping stone to Java (Jython) & plays well with C (Cython)
Sorting Cards
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You have N cards which need to be sorted in ascending
order.
Write an algorithm with the following constraints:
The cards start face down on the table
The instructions must be for only one person.
The person moving the cards can only have one card in
each hand at any point (i.e. she can only look at the
values of two cards at one time)
The instructions can't require that the person remember
the value of a card once they put it down. You can
however use the space on the table however you like.
Abstraction
• Suppose you have a randomly sorted list of integers in the
range 1 – 52
[5,6,52,24,1,43]
• And you wish to sort them in ascending order
[1,2,3,4, … 52]