giving just its filename in command linethe #line at the top then directs the unix shell to program that will run the rest of the file' code depending on the platform' install structurethe python that these #lines name might be real executableor symbolic link to version-specific executable located elsewhere these lines might also name more specific executable explicitlysuch as python either wayby changing #linessymbolic linksor path settingsunix developers can route script to the appropriate installed python none of this applies to windows itselfof coursewhere #lines have no inherent meaning python itself has historically ignored such lines as comments if present on windows ("#starts comment in the languagestillthe idea of selecting python executables on per-file basis is compelling feature in world where python and often coexist on the same machine given that many programmers coded #lines for portability to unix anyhowthe idea seemed ripe for emulating the windows legacy the install model has been very different on the other side of the fence in the past (wellin every python until )the windows installer updated the global windows registry such that the latest python version installed on your computer was the version that opened python files when they were clicked or run by direct filename in command lines some windows users may know this registry as filename associationsconfigurable in control panel' default programs dialog you do not need to give files executable privileges for this to workas you do for unix scripts in factthere' no such concept on windows--filename associations and commands suffice to launch files as programs under this install modelif you wished to open file with different version than the latest installyou had to run command line giving the full path to the python you wantedor update your filename associations manually to use the desired version you could also point generic python command lines to specific python by setting or changing your path settingbut python didn' set this for youand this wouldn' apply to scripts launched by icon clicks and other contexts this reflects the natural order on windows (when you click on doc filewindows usually opens it in the latest word installed)and has been the state of things ever since there was python on windows it' less ideal if you have python scripts that require different versions on the same machinethough-- situation that has become increasingly commonand perhaps even normal in the dual python / era running multiple pythons on windows prior to can be tedious for developersand discouraging for newcomers appendix bthe python windows launcher