'spam! 'spam!spam!spam!spam!spam!spam!spam!spam!learning by trying the immediate feedback you receive at the interactive prompt is often the quickest way to deduce what piece of code does hereit' clear that it does string repetitionin python means multiply for numbersbut repeat for strings--it' like concatenating string to itself repeatedly (more on strings in chances are good that you won' break anything by experimenting this way--at leastnot yet to do real damagelike deleting files and running shell commandsyou must really tryby importing modules explicitly (you also need to know more about python' system interfaces in general before you will become that dangerous!straight python code is almost always safe to run for instancewatch what happens when you make mistake at the interactive promptx traceback (most recent call last)file ""line in nameerrorname 'xis not defined making mistakes in pythonusing variable before it has been assigned value is always an error-otherwiseif names were filled in with defaultssome errors might go undetected this means you must initial counters to zero before you can add to themmust initial lists before extending themand so onyou don' declare variablesbut they must be assigned before you can fetch their values we'll learn more about that laterthe important point here is that you don' crash python or your computer when you make mistake this way insteadyou get meaningful error message pointing out the mistake and the line of code that made itand you can continue on in your session or script in factonce you get comfortable with pythonits error messages may often provide as much debugging support as you'll need (you'll learn more about debugging options in the sidebar "debugging python codeon page testing besides serving as tool for experimenting while you're learning the languagethe interactive interpreter is also an ideal place to test code you've written in files you can import your module files interactively and run tests on the tools they define by typing calls at the interactive prompt on the fly for instancethe following tests function in precoded module that ships with python in its standard library (it prints the name of the directory you're currently working inwith doubled-up backslash that stands for just one)but you can do the same once you start writing module files of your ownimport os os getcwd(' :\\codetesting on the fly the interactive prompt