Page - 39 - in Programming for Computations – Python - A Gentle Introduction to Numerical Simulations with Python 3.6, Volume Second Edition

2AFewMoreSteps 2.1 UsingPythonInteractively 2.1.1 TheIPythonShell Pythoncanalsobeusedinteractively, inwhichcasewedonotfirstwriteaprogram, store it in a file and then execute it. Rather, we give statements and expressions directly to what is knownas a Python shell. Thismeans that we communicatewith the Python interpretervia a particular interface. Interactiveuse of Python is a great waytoquicklydemonstratedifferentaspectsofPythonandwewilluse it repeatedly for this purpose. It is also very useful for testing out things like function behavior, syntax issues, etc., beforefinalizingrelatedcode in aprogramyouarewriting. We recommend to use IPython as shell (because it is superior to alternative Pythonshells).WithSpyder,Ipython isavailableatstartup,appearinginthelower right pane (the console).An interactive session appearsas a succession of pairwise corresponding input (to Python) and output (from Python). The user writes input commands after the IPython prompt1 In [p]:, wherep = 1,2,.. ., and gets the responseback (if any)afterOut [p]:. Thus,p serves as a counter for each pair of input and output (when there is no output, this “pair” will consist of only input). Toexemplify,we maywrite: In [1]: 2+2 Out[1]: 4 In [2]: 2*3 Out[2]: 6 In [3]: 10/2 # note: gives float Out[3]: 5.0 In [4]: 2**3 Out[4]: 8 1 A prompt means a “ready sign”, i.e. the program allows you to enter a command, and different programs often have different looking prompts. ©The Author(s) 2020 S.Linge, H.P. Langtangen, Programming forComputations -Python, Texts in Computational Science and Engineering 15, https://doi.org/10.1007/978-3-030-16877-3_2 39