evaluates to the value in the dictionary dictname coming from the key obtained by evaluating keyexpression [definition and use of dictionaries (page ) type of nonethis literal value has its own special type none indicates the absence of regular object identifiers (aidentifiers are names for python objects [literals and identifiers (page )(bthey may only contain lettersdigitsand the underscoreand cannot start with digit they are case sensitive [literals and identifiers (page )(cyou cannot use reserved word as an identifiernor are you recommended to redefine an identifier predefined by python in the idle editor you are safe if your identifier names remain colored black [literals and identifiers (page )(dby conventionmulti-word identifiers either [literals and identifiers (page ) use underscores in place of blanks (since blanks are illegal is identifiers)initial_account_balance as in ii use camel-caseall lowercase except for the starting letter of the second and later wordsas in initialaccountbalance variables are identifiers used to name python data [variables and assignment (page )when variable is used in an expressionits latest value is substituted [variables and assignment (page ) statements (aassignment statement[variables and assignment (page )variable expression the expression on the right is evaluatedusing the latest values of all variablesand calculating all operations or functions specified ii the expression value is associated with the variable named on the leftremoving any earlier association with the name (bfor-statement for item in sequence consistently indented statement blockwhich may use the variable item for each element in the sequencerepeat the statement block substituting the next element in the sequence for the variable name item see programming patterns for patterns of use [basic for loops (page )(creturn statement return expression this is used only in function definitioncausing the function to immediately terminate and return the value of expression to the calling codeeffectively acting as if the function call was replaced by this returned value [returned function values (page ) function calls functionname expression expression and so on (athe number of expressions must correspond to number of parameters allowed by the function' definition [function parameters (page ) beginning with python