operating system services hereyou will notice that the newly loaded configuration selectively replaces the parameters that were already defined moreoverif you change one of the configuration parameters that' used in variable substitutions of other configuration parametersthe changes correctly propagate for examplethe new setting of basedir in the input section affects previously defined configuration parameters in that section such as infile this behavior is an important but subtle difference between using config file and simply defining set of program parameters in python script notes two other classes can be used in place of configparser the class rawconfigparser provides all of the functionality of configparser but doesn' perform any variable interpolation the safeconfigparser class provides the same functionality as configparserbut it addresses some subtle problems that arise if configuration values themselves literally include special formatting characters used by the interpolation feature ( '%'datetime the datetime module provides variety of classes for representing and manipulating dates and times large parts of this module are simply related to different ways of creating and outputting date and time information other major features include mathematical operations such as comparisons and calculations of time deltas date manipulation is complex subjectand readers would be strongly advised to consult python' online documentation for an introductory background concerning the design of this module date objects date object represents simple date consisting of yearmonthand day the following four functions are used to create datesdate(yearmonthdaycreates new date object year is an integer in the range datetime minyear to datetime maxyear month is an integer in the range to and day is an integer in the range to the number of days in the given month the returned date object is immutable and has the attributes yearmonthand day corresponding to the values of the supplied arguments date today( class method that returns date object corresponding to the current date date fromtimestamp(timestampa class method that returns date object corresponding to the timestamp timestamp timestamp is value returned by the time time(function date fromordinal(ordinala class method that returns date object corresponding to an ordinal number of days from the minimum allowable date (january of year has ordinal value and january has ordinal value lib fl ff