Python 2.X Command Options
Python 2.X supports the same command-line format, but does not support the -b option, which is related to Python 3.X’s string type changes, nor the recent –q and –X additions in 3.X. It supports additional options in 2.6 and 2.7 (some may be present earlier):
-t and -tt
Issues warnings for inconsistent mixtures of tabs and spaces in indentation. Option -tt issues errors instead. Python 3.X always treats such mixtures as syntax errors (see also Syntax Rules).
-Q
Division-related options: -Qold (the default), -Qwarn, -Qwarnall, and –Qnew. These are subsumed by the new true division behavior of Python 3.X (see also Operator Usage Notes).
-3
Issues warnings about any Python 3.X incompatibilities in code that the Python standard installation’s 2to3 tool cannot trivially fix.
-R
Enables a pseudorandom salt to make hash values of various types be unpredictable between separate invocations of the interpreter, as a defense against denial-of-service attacks. New in Python 2.6.8. This switch is also present in 3.X as of 3.2.3 for compatibility, but this hash randomization is enabled by default as of 3.3.