Chapter 2. Using the Python Interpreter 6 Python Tutorial, Release 3.9.5 2.1.1 Argument Passing When known to the interpreter, the script name and additional arguments thereafter are turned into a list of strings and assigned to the$_{argv}$variable in the$_{sys}$ module. You can access this list by executing$_{import sys}$. The length of the list is at least one; when no script and no arguments are given, sys.argv[0] is an empty string. When the script name is given as '-' (meaning standard input), sys.argv[0] is set to '-' . When -c command is used, sys.argv[0] is set to '-c' . When -m module is used, sys.argv[0] is set to the full name of the located module. Options found after$_{-c}$ command or$_{-m}$ module are not consumed by the Python interpreter’s option processing but left in$_{sys.argv}$ for the command or module to handle. When commands are read from a tty, the interpreter is said to be in interactive mode . In this mode it prompts for the next command with the primary prompt , usually three greater-than signs ( >>> ); for continuation lines it prompts with the secondary prompt , by default three dots ( ... ). The interpreter prints a welcome message stating its version number and a copyright notice before printing the first prompt: 2.1.2 Interactive Mode $ python3.9 Python 3.9 (default, June 4 2019, 09:25:04) [GCC 4.8.2] on linux Type "help", "copyright", "credits" or "license" for more information. > >> >>> the_world_is_flat = True >>>if the_world_is_flat: ... print("Be careful not to fall off! ") ... Be careful not to fall off! Continuation lines are needed when entering a multi-line construct. As an example, take a look at this$_{if}$ statement: For more on interactive mode, see Interactive Mode . By default, Python source files are treated as encoded in UTF-8. In that encoding, characters of most languages in the world can be used simultaneously in string literals, identifiers and comments — although the standard library only uses ASCII characters for identifiers, a convention that any portable code should follow. To display all these characters properly, your editor must recognize that the file is UTF-8, and it must use a font that supports all the characters in the file. To declare an encoding other than the default one, a special comment line should be added as the first line of the file. The syntax is as follows: where encoding is one of the valid$_{codecs}$supported by Python. For example, to declare that Windows-1252 encoding is to be used, the first line of your source code file should be: One exception to the first line rule is when the source code starts with a UNIX “shebang” line . In this case, the encoding declaration should be added as the second line of the file. For example: # -*- coding: cp1252 -*- # -*- coding: encoding -*- 2.2 The Interpreter and Its Environment 2.2.1 Source Code Encoding