Python Setup and Usage, Release 3.9.5 9 1.2. Environment variables PYTHONPLATLIBDIR PYTHONSTARTUP PYTHONOPTIMIZE PYTHONBREAKPOINT PYTHONDEBUG PYTHONOLDPARSER PYTHONINSPECT PYTHONUNBUFFERED PYTHONVERBOSE PYTHONCASEOK PYTHONPYCACHEPREFIX PYTHONDONTWRITEBYTECODE PYTHONHASHSEED If this variable is not set or set to$_{random}$, a random value is used to seed the hashes of str and bytes objects. New in version 3.8. If this is set, Python will write$_{.pyc}$ files in a mirror directory tree at this path, instead of in$_{__pycache__}$ directories within the source tree. This is equivalent to specifying the$_{-X}$$_{pycache_prefix=PATH}$option. If this is set to a non-empty string, Python won’t try to write$_{.pyc}$ files on the import of source modules. This is equivalent to specifying the$_{-B}$option. If this is set, Python ignores case in$_{import}$ statements. This only works on Windows and OS X. If this is set to a non-empty string it is equivalent to specifying the$_{-v}$ option. If set to an integer, it is equivalent to specifying$_{-v}$ multiple times. If this is set to a non-empty string it is equivalent to specifying the$_{-u}$option. This variable can also be modified by Python code using$_{os.environ}$ to force inspect mode on program termination. If this is set to a non-empty string it is equivalent to specifying the$_{-i}$option. Deprecated since version 3.9, will be removed in version 3.10. See also the$_{-X}$$_{oldparser}$option and PEP 617 . If this is set to a non-empty string, enable the traditional LL(1) parser. If this is set to a non-empty string it is equivalent to specifying the$_{-d}$option. If set to an integer, it is equivalent to specifying$_{-d}$multiple times. New in version 3.7. If this is set, it names a callable using dotted-path notation. The module containing the callable will be imported and then the callable will be run by the default implementation of sys.breakpointhook() which itself is called by built-in breakpoint() . If not set, or set to the empty string, it is equiva- lent to the value “pdb.set_trace”. Setting this to the string “0” causes the default implementation of$_{sys.}$ breakpointhook() to do nothing but return immediately. If this is set to a non-empty string it is equivalent to specifying the$_{-O}$option. If set to an integer, it is equivalent to specifying -O multiple times. Raises an auditing event$_{cpython.run_startup}$ with the filename as the argument when called on startup. If this is the name of a readable file, the Python commands in that file are executed before the first prompt is displayed in interactive mode. The file is executed in the same namespace where interactive commands are executed so that objects defined or imported in it can be used without qualification in the interactive session. You can also change the prompts$_{sys.ps1}$ and$_{sys.ps2}$ and the hook$_{sys.__interactivehook__}$ in this file. New in version 3.9. If this is set to a non-empty string, it overrides the sys.platlibdir value.