to find its own libraries and the site-packages directory where extensions are normally installed if single directory such as /usr/local is giventhe interpreter expects to find all files in that location if two directories are givensuch as /usr/local:/usrlocal/sparc-solaris- the interpreter searches for platform-independent files in the first directory and platform-dependent files in the second pythonhome has no effect if no valid python installation exists at the specified location the pythonioencoding environment setting might be of interest to users of python because it sets both the encoding and error handling of the standard / streams this might be important because python directly outputs unicode while running the interactive interpreter prompt thisin turncan cause unexpected exceptions merely while inspecting data for examplea 'jalape\xf oa traceback (most recent call last)file ""line in file "/tmp/lib/python /io py"line in write encoder encode(sfile "/tmp/lib/python /encodings/ascii py"line in encode return codecs ascii_encode(inputself errors)[ unicodeencodeerror'asciicodec can' encode character '\xf in position ordinal not in range( to fix thisyou can set the environment variable pythonioencoding to something such as 'ascii:backslashreplaceor 'utf- nowyou will get thisa 'jalape\xf oa 'jalape\xf oon windowssome of the environment variables such as pythonpath are additionally read from registry entries found in hkey_local_machine/software/python interactive sessions if no program name is given and the standard input to the interpreter is an interactive terminalpython starts in interactive mode in this modea banner message is printed and the user is presented with prompt in additionthe interpreter evaluates the script contained in the pythonstartup environment variable (if setthis script is evaluated as if it' part of the input program (that isit isn' loaded using an import statementone application of this script might be to read user configuration file such as pythonrc when interactive input is being acceptedtwo user prompts appear the prompt appears at the beginning of new statementthe prompt indicates statement continuation here' an examplefor in range( , )print lib fl ff