Identify The Program (-c, -m, -, file ). The -c option provides the Python program on the command line as a quoted string. This isn't terribly useful. However, we can use it for things like the following.

python -c 'import sys; print sys.version'

Note the rarely-used ; to terminate a statement.

The -m option will locate a module on the PYTHONPATH and execute that module. This allows you to install a complete application in the Python library and execute the top-level "main program" script.

As we noted in the section called “Script Mode”, the command-line argument to the Python interpreter is expected to be a Python program file. Additionally, we can provide a Python program on standard input and use python - to read and process that program.

Select the Division Operator Semantics (-Q). As we noted in the section called “Division Operators”, there are two senses for division. You can control the meaning of / using -Qnew and -Qold. You can also debug problems with -Qwarn or -Qwarnall. Rather than rely on -Qnew, you should include from __future__ import division in every program that uses the new // operator and the new sense of the / operator.

Optimization (-O). We can use -O and -OO to permit some optimization of the Python bytecode. This may lead to small performance improvements.

Generally, there are two sources for performance improvements that are far more important than optimization. First, and most fundamentally, correct choices of data structures and algorithms have the most profound influence on performance. Second, modules can be written in C and use the Python API's. These C-language modules can dramatically improve performance, also.

Startup and Loading (-S, -E). There are several ways to control the way Python starts and which modules it loads.

The -E option ignores all environment variables (PYTHONPATH is the most commonly used environment variable.)

Ordinarily Python executes an implicit import site when it starts executing. The site module populates sys.path with standard locations for packages and modules. The -S option will suppress this behavior.

Debugging (-d, -i, -v, -u). Python has some additional debugging information that you can access with the -d option. The -i option will allow you to execute a script and then interact with the Python intrpreter. The -v option will display verbose information on the import processing.

Sometimes it will help to remove the automatic buffering of standard output. If you use the -u option, mixed stderr and stdout streams may be easier to read.

Indentation Problem-Solving (-t, the TabNanny, and -x). The -t option gives warning on inconsistent use of tabs and spaces. The -tt option makes these warnings into errors, stopping your program from running.

The -x option skips the first line of a file. This can be used for situations where the first line of a Python file can't be a simple #! line. If the first line can't be a comment to Python, this will skip that line.