Seite - 18 - in Programming for Computations – Python - A Gentle Introduction to Numerical Simulations with Python 3.6, Band Second Edition

18 1 TheFirstFewSteps 1.4.3 ImportswithNameChange Whetherweimport forusewithorwithoutprefix,wemaychangenamesof the im- porteditemsbyminoradjustmentsof the importstatements. Introducingsuchname changes in our program and saving this final version ascheck_functions.py, it reads import numpy as np import math as m x = np.exp([0, 1, 2]) # do all 3 calculations print(x) # print all 3 results y = m.cos(0) print(y) Effectively, the module names in this program now become np and m (by our own choice) instead of numpy and math, respectively. We still enjoy the safety of prefixing and notice that such name changes might bring computer coded expressionscloser to mathematicalwritingand thusease humaninterpretation. When importinglibrary itemsforusewithoutprefix,namechangescanbedone, e.g., like from math import cos as c, sin as s print(c(0) + s(0)) 1.4.4 ImportingfromPackages Modules may be grouped into packages, often together with functions, variables, and more. We may import items (modules, functions, etc.) from such packages also, but the appearance of an import statement will then depend on the structure of the package in question. We leave out the details14 and just exemplify with two packagesoftenused in thisbook. Thenumpy library used above is, in fact, a packageand we saw how it could be used with different import statements, just as if it had been a module.Note that the import statement import numpy as np # standard way of importing numpy is the standard way of importingnumpy, i.e., also the “nickname”np is standard. Thiswillbe thestandardimport techniquefornumpyalso inourbook,meaningthat we will generally usenumpy items with thenpprefix. We will deviate from this at times, typically during brief interactive sessions (see Sect.2.1), in which case we will import itemsexplicitlyspecifiedbyname. Anotherpopularpackageyouwill meetoften in thisbook, is the plotting library matplotlib (Sect.1.5), used for generating and handling plots. The standard import statement, including the“nickname”, is then import matplotlib.pyplot as plt # standard way of importing pyplot 14 If you are curious, check for more details athttps://docs.python.org/3.6/tutorial/modules.html.