part igetting started with python -xskip the first line of source code filewhich allows the use of nonunix forms of #!cmd - optset an implementation-specific option (the documentation for your version of python discusses these optionsif there are any using python environment variables to your advantage environment variables are special settings that are part of the command line or terminal environment for your operating system they serve to configure python in consistent manner environment variables perform many of the same tasks as do the options that you supply when you start pythonbut you can make environment variables permanent so that you can configure python the same way every time you start it without having to manually supply the option as with optionsmost of these environment variables won' make any sense right now you can read through them to see what is available you find some of the environment variables used later in the book feel free to skip the rest of this section and come back to it later when you need it most operating systems provide the means to set environment variables temporarilyby configuring them during particular sessionor permanentlyby configuring them as part of the operating system setup precisely how you perform this task depends on the operating system for examplewhen working with windowsyou can use the set command (see my blog post at johnmuellerbooks com//using-the-set-command-toyour-advantagefor detailsor rely on special windows configuration feature (see my post at adding- -location-to-the-windows-pathfor setting the path environment variable as an exampleusing environment variables makes sense when you need to configure python the same way on regular basis the following list describes the python environment variablespythoncaseok=xforces python to ignore case when parsing import statements this is windows-only environment variable pythondebug=xperforms the same task as the - option pythondontwritebytecode=xperforms the same task as the - option