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RE INTRODUCTION TO PROGRAMMING Where we hope to teach the fundamentals of programming and create connecti ons between those elements and previous experience with Mathematica BASIC PROGRAMMING PROGRAMMING LANGUAGES Needed as human language is ambiguous Computer code composed of: Syntax – structure of code Semantics - meaning of code High level Python C++ Perl Java Ruby Low level Machine Assembly Forth C G-code M a c h in e I n s t r u c t i o n s : load the number from memory location 2001 into the CPU load the number from memory location 2002 into the CPU add the two numbers in the CPU store the results in location 2003 Python Input: c=a+b TRANSLATING HIGH LEVEL LANGUAGES Translation methods: 1. Compiler takes high-level code and translated into machine language 2. Interpreter simulates a computer that understands high-level language Main Differences Compiler Interpreter Occur s only once & may be run many times af ter Tend to run faster Used ever y time program runs Lend to more flexible programming PYTHON “A r e yo u s u g g e s t i n g c o c o n u t s m i g r a te ? ” “ N o t a t a l l . T h ey c o u l d b e c a r r i e d ” “ W h a t ? A s wa l l o w c a r r y i n g a c o c o n u t ? ” “ I t c o u l d g r i p i t by t h e h u s k ! ” “It's not a question of where he grips it! It's a simple question o f we i g h t r a t i o s ! A f i v e o u n c e b i r d c o u l d n o t c a r r y a o n e p o u n d coconut.” BASIC INFORMATION Creator: Guido Van Rossum Where: Netherlands When: late 1980s Download Options: Python 3.3.2 Python 2.7.5 IronPython—running on .Net Jython—running on Java vir tual machine PyPy—fast Python implementation with a JIT compiler Stackless Python—branch of Cpython Python(x,y)—scientific-oriented Python …and so on SNY TAX & BASIC SEMANTICS >>> # print def name(): Prompt Used to mark off the start of a comment returns a desired output to the shell Used create a new function Python 2.7.3 (default, Apr 10 2012, 23:31:26) [MSC v.1500 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information. Imported NumPy 1.6.2, SciPy 0.11.0, Matplotlib 1.1.1 + guidata 1.5.1, guiqwt 2.2.1 Type "scientific" for more details. >>> #>>> is a Python prompt indicating that it is ready for a command. >>> #A complete command is called a sentence. >>> print "Hello, World" Hello, World >>> def hello(): print “Hello” >>> hello(): Hello LOOPS Definite Executed definite no. of times For Loop: for <var> in <sequence>: <body> for i in range (10): print i Indefinite/Conditional Iterates until certain conditions are met While loop: while <condition>: <body> Danger of infinite loops Break out by pressing Ctrl+c Ctrl+Alt+Delete if nonresponsive If all else fails, restart computer manually DECISION STRUCTURES If statement: if <condition>: <body> If/else statement: if <condition>: <statement> else : <statement> If/elif/else statement if <condition>: <statement> elif <condition>: <statement> else : <statement> Python Meaning < Less than <= Less than or equal to == Equal to >= Greater than or equal to > Greater than != Not equal to EXCEPTION HANDLING try: <body> Except <ErrorType>: <handler> def quadSolver(a,b,c): try: discrim=math.sqrt(b*b-4*a*c) root1=(-b+discRoot)/(2*a) root2=(-b-discRoot)/(2*a) print "\nThe solutions are:", root1,"&", root2 except ValueError: print “\nNo real roots.” ADDITIONAL RESOURCES Python Resources: Code Academy: Python Pythonanywhere Python Programming: An Introduction to Computer Science John M. Zelle Other Coding Resources: Code Academy
