from abc import abstractmethod

class IExporter:
    @abstractmethod
    def setData(self, data):
        pass
    
    @abstractmethod
    def prepareAuthorsList(self):
        pass
    
    @abstractmethod
    def prepareAbstractsList(self):
        pass
    
    @abstractmethod
    def getDatabaseForExport(self):
        pass

class ExportXML(IExporter):
    def __init__(self):
        self.__result = ''
        print('XML exporter works')
    
    def setData(self, data):
        self.__data = data
    
    def prepareAuthorsList(self):
        self.__result += '<authors>\n'
        for author in self.__data[0]:
            self.__result += '\t<author>' + author + '</author>\n'
        self.__result += '</authors>\n'
    
    def prepareAbstractsList(self):
        self.__result += '<abstracts>\n'
        for abstract in self.__data[1]:
            self.__result += '\t<abstract>' + abstract + '</abstract>\n'
        self.__result += '</abstracts>\n'
    
    def getDatabaseForExport(self):
        return '<xml>\n' + self.__result + '</xml>\n'

class ExportJSON(IExporter):
    def __init__(self):
        self.__result = ''
        print('JSON exporter works')
    
    def setData(self, data):
        self.__data = data
    
    def prepareAuthorsList(self):
        self.__result += '{"authors": \n'
        for author in self.__data[0]:
            self.__result += '\t{"author": ' + author + '}\n'
        self.__result += '},\n'
    
    def prepareAbstractsList(self):
        self.__result += '{"abstracts":\n'
        for abstract in self.__data[1]:
            self.__result += '\t{"abstract:"' + abstract + '}\n'
        self.__result += '},\n'
    
    def getDatabaseForExport(self):
        return '{"Book of abstracts":\n' + self.__result + '}\n'

class DatabaseExporter:
    def __init__(self, concreteBuilder):
        self._builder = concreteBuilder
    
    def getDatabase(self, data):
        self._builder.setData(data)
        self._builder.prepareAuthorsList()
        self._builder.prepareAbstractsList()
        return self._builder.getDatabaseForExport()

data = [
    ['Alice', 'Bob', 'Candy', 'Denis'],
    ['Lorem ipsum 01', 'Lorem ipsum 02', 'Lorem ipsum 03', 'Lorem ipsum 04', 'Lorem ipsum 05', 'Lorem ipsum 06']
]

class Numeric:
    @abstractmethod
    def evaluate(self):
        pass

class NumericOperand(Numeric):
    def __init__(self, number):
        self.__value = number
    
    def evaluate(self):
        return self.__value

class CompositeOperand(Numeric):
    def __init__(self, lhs, rhs, operation):
        self.__lhs = lhs
        self.__rhs = rhs
        self.__operation = operation
    
    def evaluate(self):
        lft = self.__lhs.evaluate()
        rht = self.__rhs.evaluate()
        
        if self.__operation == '+':
            return lft + rht
        elif self.__operation == '-':
            return lft - rht
        elif self.__operation == '*':
            return lft * rht
        elif self.__operation == '/':
            return lft / rht