ii iii iv sscasc@tumkur only alphabetsdigits and underscores are permitted distinguish between uppercase and lowercase alphabets keywords should not be used as identifiers no blank space between the identifiers valid identifiers area area_tri num keywordsthe keywords have predefined meaning assigned by the python complier the keywords are also called as reserved word all keywords are written in lower case alphabets the python keywords areand del for lambda true as elif from not try assert else global or while break except if pass with class exec import print yield continue false in raise def finally is return variableis program elementwhose value changes during the execution of the program unlike other programming languagespython has no command for declaring variable variable is created the moment you first assign value to it eg = ="kvnvariables do not need to be declared with any particular type and can even change type after they have been set constantsconstant is program elementwhile execution of program the value does not change constant gets stored in memory location but the address of the location is not accessible to the programmer assigning value to constant in python in pythonconstants are usually declared and assigned on module herethe module means new file containing variablesfunctions etc which is imported to main file sp_python programming