Seite - 3 - in Programming for Computations – Python - A Gentle Introduction to Numerical Simulations with Python 3.6, Band Second Edition

1.1 What IsaProgram?AndWhat IsProgramming? 3 do? Well, you may write down the recipe in those three languages and send them over. Now, if you have been able to think correctly when writing down the recipe, andyouhavewritten theexplanationsaccordingto the rules ineach language,each ofyourfriendswillproducethesamecake.Yourrecipe is the“computerprogram”, while English, Russian and Chinese represent the “computer languages” with their own rules of how to write things. The end product, though, is still the same cake. Note that you may unintentionally introduce errors in your “recipe”. Depending on the error, this may cause “baking execution” to stop, or perhaps produce the wrong cake. In your computer program, the errors you introduce are called bugs (yes,small insects! ...forhistoricalreasons),andtheprocessoffixingthemiscalled debugging.When you try to run yourprogramthat containserrors, you usually get warningsorerrormessages.However,theresponseyougetdependsontheerrorand the programming language. You may even get no response, but simply the wrong “cake”. Note that the rules of a programming language have to be followed very strictly. This differs from languages like English etc., where the meaning might be understoodevenwith spellingerrorsand“slang” included. We Use Python 3.6 in This Book For good reasons, the programming language used in this book is Python (version 3.6). It is an excellent language for beginners (and experts!), with a simple and clear syntax. Some of Python’s other strong properties are1: It has a huge and excellent library (i.e., ready-made pieces of code that you can utilize for certain tasks in your own programs), many global functionscan be placed in onlyone file, functionsare straightforwardly transferred as arguments to other functions, there is good support for interfacing C, C++ and Fortrancode (i.e., a Pythonprogrammayuse code written in other languages),and functions explicitly written for scalar input often work fine, without modification, also with vector input.Another important thing, is that Python is available for free. It canbedownloadedatnocost fromthe Internetandwill runonmostplatforms. APrimer onScientific Programmingwith Python Readers who want to expand their scientific programming skills beyond the introductorylevelof thepresentexposition,areencouragedtostudyAPrimer on Scientific Programming with Python [11]. This comprehensive book is as suitable for beginners as for professional programmers, and teaches the art of programming through a huge collection of dedicated examples. This book is considered the primary reference, and a natural extension, of the programmingmatters in the present book. Note, however, that this reference [11]usesversion2.7ofPython,whichmeansthat, ina fewcases, instructions will differ somewhat fromwhatyoufindin thepresentbook. 1 Some of the words here will be new to you, but relax, they will all be explained as we move along.