>>> bill = 100 >>> bill *= 1.08 >>> bill 108.0 >>>
On Saturday, November 21, 2015 at 9:47:29 PM UTC+8, Frank Millman wrote: > "Cai Gengyang" wrote in message > news:a76b1b5b-4321-41bb-aeca-0dac78775...@googlegroups.com... > > > This is a piece of code that calculates tax and tip : > > > > def tax(bill): > > """Adds 8% tax to a restaurant bill.""" > > bill *= 1.08 > > print "With tax: %f" % bill > > return bill > > > > def tip(bill): > > """Adds 15% tip to a restaurant bill.""" > > bill *= 1.15 > > print "With tip: %f" % bill > > return bill > > > > meal_cost = 100 > > meal_with_tax = tax(meal_cost) > > meal_with_tip = tip(meal_with_tax) > > > > Does bill *= 1.08 mean bill = bill * 1.15 ? > > Firstly, I assume that you actually meant 'bill = bill * 1.08' at the end of > the last line. > > Secondly, how can I help you to answer this kind of question yourself. > > Here are two ways. > > 1. Try it out at the interpreter - > > c:\> > Python 3.4.3 (v3.4.3:9b73f1c3e601, Feb 24 2015, 22:44:40) [MSC v.1600 64 bit > (AMD64)] on win32 > Type "help", "copyright", "credits" or "license" for more information. > >>> bill = 100 > >>> bill *= 1.08 > >>> bill > > I deliberately omitted the last line. Try it yourself and see what you get. > > 2. Read the fine manual. > > The Index has a section headed 'Symbols'. From there you will find '*=', > with a link to 'augmented assignment'. > > If you follow the link, you will find a detailed explanation. Here is an > excerpt - > > "An augmented assignment expression like x += 1 can be rewritten as x = x + > 1 to achieve a similar, but not exactly equal effect. In the augmented > version, x is only evaluated once. Also, when possible, the actual operation > is performed in-place, meaning that rather than creating a new object and > assigning that to the target, the old object is modified instead." > > Frank Millman -- https://mail.python.org/mailman/listinfo/python-list