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Python辅导 | CS1026: Assignment 4: Country Classes

这个Assignment是使用python列表,面向对象等完成一个有关国家的小练习
CS1026: Assignment 4: Country Classes
Due: Thursday, December 5th 2019 at 9:00pm
Weight: 12%

Learning Outcomes:
By completing this assignment, you will gain skills relating to
 Strings and text files
 Writing and using your own classes
 Testing code
 Using complex data structures (i.e., lists, sets and dictionaries)
Data files are very common in many disciplines. They form the input for a variety of different kinds of
processing, analysis, summaries, etc. An associated problem is to maintain these data files – to add
information, update or correct information. Manually updating data files can be tedious and can lead
to errors. A common approach is to use a program – an “update” program that takes a data file and a
file of “updates” and then creates a new version of the data file with the updates applied.
In this assignment you will create a complete program that will update an existing data file containing
information about countries. The tasks are outlined below.
Tasks
TASK 1
Implement a class Country that holds the information about a single country; name the file
country.py.
Instance Variables
1) name: The name of the country (string)
2) population: The population in the country (integer)
3) area: The area of the country (integer)
4) continent: The name of the continent to which the country belongs (string)
Methods
1) Constructor, __init__(self, name, pop, area, continent)
2) Getter Methods: getName, getPopulation, getArea, getContinent
3) Setter Methods: setPopulation, setArea, setContinent
4) def __repr__(self): generates a string representation for class objects.
Example of output from __repr__
Name (pop: population value, size: area value) in Continent
e.g., Nigeria (pop: 11723456, size: 324935) in Africa
Test all your classes and methods before moving to the next section. Feel free to
create other helper methods if necessary.
TASK 2
Implement a class called CountryCatalogue; name the file catalogue.py .
This class will use a file to build the data structures to hold the information about countries. The file
data.txt contains information about a number of countries. An example of the data file is:
Country|Continent|Population|Area
Brazil|South America|193,364,000|8,511,965
Canada|North America|34,207,000|9,976,140
China|Asia|1,339,190,000|9,596,960
Colombia||48,654,392|1,090,909
Egypt|Africa|93,383,574|
Notice that:
 There is a header line: “Country|Continent|Population|Area”. This is really for
information purpose for the data file; it is a reminder of the format of the data in the file.
 The file consists of “records” for each country – one per line with the information as described
in the header line.
 The different “fields” of each “record” are separated by vertical bars, “|”.
 A field (except for country name) may be missing (see Colombia and Egypt) but the record
should still have the three vertical bars.
The class CountryCatalogue should have the following instance variable:
1. countryCat: This is a collection of countries, i.e., each member is an object of the class Country.
The collection could be a set, dictionary or list. It is important that the collection store objects of
type Country.
You may add other instance variables as you see fit.
Methods
1) Constructor, __init__(self, countryFile)
The constructor method will take a single parameter (besides “self”) that is the name of the file
that contains the information about each country. The constructor will use the data in the file to
construct the data structure countryCat. Sample data files has been provided: data.txt and
data2.txt. [Note: Both files have headers and these files are meant for you to test your program;
they may NOT be the same used to evaluate your solution.]
2) Setter Methods: setPopulationOfCountry, setAreaOfCountry, setContinentOfCountry
3) findCountry(self,country)
Given a country object (that is, an object of the Country class), this methods checks to see if that
country object is in countryCat . If it is, it just returns the country object, but if it is not, it returns
the null object NONE.
4) addCountry(self,countryName,pop,area,cont)
Given the name, population, area and continent of a country, this method adds a new country to
countryCat; it should only be added if the country does not exist in countryCat . The method
should return True if the operation is successful (country successfully added), or False if it is not,
e.g. the country they entered already exists.
5) printCountryCatalogue(self)
This method prints a list of the countries and their information to the screen; it should make use
of the repr method of the Country class.
6) saveCountryCatalogue(self,fname)
This method will enable all the country information in the catalogue to be saved to a file. The
method takes as a parameter the name of the file. All the countries should be sorted
alphabetically by name (A – Z) prior to saving. If the operation is successful, the method should
return the number of items written, otherwise it should return a value of ‐1. The file should
appear in the exact same format as the original file, namely:
Country|Continent|Population|Area
Brazil|South America|193,364,000|8,511,965
Canada|North America|34,207,000|9,976,140
China|Asia|1,339,190,000|9,596,960
Egypt||93,384,001|1,000,000
Indonesia||260,581,345|
Notice that:
 There should be no spaces between the fields and vertical bars.
 If a field has no value, then nothing should be printed, e.g. see Egypt and Indonesia with no
continent value and Indonesia with no area given.
You may add other methods as you see fit.
Test all your classes and methods before moving to the next section. Feel free to
create other helper methods if necessary.
TASK 3
Implement a Python module, called processUpdates.py, that has a function
processUpdates(cntryFileName,updateFileName). This function takes two parameters: the first
parameter will be the name of a file containing country data (e.g. data.txt). The second file will
contain the name of a file containing updates. Each record in the update file specifies updates for a
single country. The format of a record is as follows:
Country;update1;update2;update3
Where an “update” is of the form “L=value” and L can be P, for population, A for area and C for
continent. Updates are separated by semicolons and a line can have 0, 1, 2 or 3 updates; any updates
beyond 3 are simply ignored.
An example of an update file is:
Brazil;P=193,364,111;A=8,511,966
Indonesia;P=260,581,345
Japan;P=127,380,555;A=377,800
Sweden;P=9,995,345;A=450,295;C=Europe
Italy; P=59,801,999
Canada;C=North America
Egypt;A=1,000,000 ; P=93,384,001
Notice that:
 The updates can be in different orders, e.g. the updates for Egypt are area first, then
population.
 If a country is specified and that country is NOT already in the catalogue then that country
and its attributes (at least the ones specified; not all have to be specified) should be
added to the catalogue.
 There can be spaces around the semicolons; spaces in other places may cause errors and
should be handled as exceptions (see below).
The function processUpdates gets two files as parameters. The first parameter is the name of the file
with the country data and the second parameter is the name of file with the update data.
The country file should be processed first. The function processUpdates should ensure that it exists.
If it does exist, it should then proceed to process the data file using the class CountryCatalogue. If the
country file does not exist, then processUpdates should give the user the option to quit or not
(prompts for “Y” (yes) or “N” (no)). If the user does not wish to quite (responds with “N”), then the
function should prompt the user for the name of a new file. If the user wishes to quit (responds with
a “Y” or anything other than a “N”, then the method should exit and return False. The method should
continue to prompt for file names until a valid file is found or the user quits.
If the user chooses to quit, i.e. no country file is processed, then the function processUpdates should
NOT try to process the updates file, write to the file “output.txt” the message “Update
Unsuccessful\n” – just the single line. It should then exit (i.e.,) and return False.
If the function processUpdates has successfully processed the country file, then it should proceed to
process the file of updates. It should prompt the user in a similar manner to how the country file was
input, i.e., using a loop to continuously prompt the user until a file was found that existed or until the
user quits.
If the user quits without an update file being selected, then the function processUpdates should write
to the file “output.txt” the message “Update Unsuccessful\n” – just the single line. It should then
exit (i.e.,) and return False.
If an update file is found, then the function processUpdates should process the updates, i.e., update
the information about the countries and then output the new updated list of countries in alphabetical
order to the file “output.txt”. The output should use the method saveCountryCatalogue(self,fname)
from the class CountryCatalogue (see Task 2). It should then exit and return True.
In processing the updates from the update file, the lines may have extra spaces, forgotten semicolons,
etc. Some of these MAY cause exceptions when processing the line – you program should be design
to catch any of these as exception. , e.g. bad values, incorrect format, etc.
The main.py file is provided as the interface to your program. It has been designed to prompt for the
names of a country file and a file of updates and then call the function processUpdates; make sure
that you use these names of functions and methods as described above. You may use the main.py
to test your program in other ways. Two additional data sets of countries have been provided,
data2.txt and data3.txt, as well as two different files of updates, upd2.txt and upd3.txt. You may use
these to test your program. NOTE: while main.py will test some aspects of your program it does not
do a complete and thorough testing – this is left up to you. The TA will use a program similar to,
but different than, main.py to grade your assignment ‐ it will include other tests.
The following may be helpful in sorting data structures
http://pythoncentral.io/how‐to‐sort‐a‐list‐tuple‐or‐object‐with‐sorted‐in‐python/
http://pythoncentral.io/how‐to‐sort‐python‐dictionaries‐by‐key‐or‐value/
Non‐functional Specifications:
1. Include brief comments in your code identifying yourself, describing the program, and describing
key portions of the code.
2. Assignments are to be done individually and must be your own work. Software may be used to
detect cheating.
3. Use Python coding conventions and good programming techniques, for example:
i. Meaningful variable names
ii. Conventions for naming variables and constants
iii. Readability: indentation, white space, consistency
Submit the files in which your classes and functions are defined:
 country.py containing the class Country;
 catalogue.py containing the class CountryCatalogue;
 processUpdates.py contain the function processUpdates.
Make sure you attach your python file to your assignment; DO NOT put the code inline in the textbox.
What You Will Be Marked On:
1. Functional specifications:
 Does the program behave according to specifications? Are classes, methods and functions
named as per the instructions?
 Are the order of parameters in the methods and functions defined as per the instructions?
 Does it run when tested with a program similar to the main program provided?
 Are your classes created properly?
 Are you using appropriate data structures?
 Is the output according to specifications?
2. Non‐functional specifications: as described above
3. Assignment submission: via OWL assignment submission


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