3 CHAPTER ONE COMMAND LINE AND ENVIRONMENT The CPython interpreter scans the command line and the environment for various settings. CPython implementation detail: Other implementations’ command line schemes may differ. See implementations for further resources. When invoking Python, you may specify any of these options: python [-bBdEhiIOqsSuvVWx?] [-ccommand| -m module-name | script | - ] [args] The most common use case is, of course, a simple invocation of a script: python myscript.py The interpreter interface resembles that of the UNIX shell, but provides some additional methods of invocation: In non-interactive mode, the entire input is parsed before it is executed. An interface option terminates the list of options consumed by the interpreter, all consecutive arguments will end up in$_{sys.argv}$ – note that the first element, subscript zero ($_{sys.argv[0]}$ ), is a string reflecting the program’s source. Execute the Python code in command . command can be one or more statements separated by newlines, with significant leading whitespace as in normal module code. If this option is given, the first element of$_{sys.argv}$ will be$_{"-c"}$ and the current directory will be added to the start of$_{sys.path}$(allowing modules in that directory to be imported as top level modules). -c <command> 1.1.1 Interface options 1.1 Command line • When called with$_{-m module-name}$ , the given module is located on the Python module path and executed as a script. • When called with$_{-c command}$ , it executes the Python statement(s) given as command . Here command may contain multiple statements separated by newlines. Leading whitespace is significant in Python statements! • When called with a directory name argument, it reads and executes an appropriately named script from that directory. • When called with a file name argument or with a file as standard input, it reads and executes a script from that file. • When called with standard input connected to a tty device, it prompts for commands and executes them until an EOF (an end-of-file character, you can produce that with$_{Ctrl-D}$ on UNIX or$_{Ctrl-Z, Enter}$ on Windows) is read.