Python - 字典，泡菜

Question

I'm taking an intro to Python class and I can't get my program to work. Here is the project explanation:

• Create a class named "Nation" with four instance variables to hold the data for a country and a method named popDensity that calculates the population density of the country. Write a program that uses the class to create a dictionary of 193 items, where each item of the dictionary has the form: name of a country: Nation object for that country
  Use the file "UN.txt" to create the dictionary, and save the dictionary in a pickled binary file named nationsDict.dat.

The "UN.txt" file basically contains a listing of country, continent, population, area (Example: Albania,Europe,3.0,11100)

Here is the program I created (using pythonanywhere.com):

import pickle

def main():
    createDictionaryofNations()

def createDictionaryofNations():
    nationdict = {}
    for line in open("UN.txt", 'r'):
        data = line.split(',')
        country = Nation()
        country.setName(data[0])
        country.setContinent(data[1])
        country.setPopulation (float(data[2]))
        country.setArea (float(data[3].rstrip()))
        nationdict[country.getName()] = country

    pickle.dump(nationdict, open("nationdict.dat", 'wb'))
    return nationdict

class Nation:
    def __init__(self):
        self._name = ""
        self._continent = ""
        self._population = 0.0
        self._area = 0

    def setName(self, name):
        self._name = name

    def getName(self):
        return self._name

    def setContinent(self, continent):
        self._continent = continent

    def getContinent(self):
        return self._continent

    def setPopulation(self, population):
        self._population = population

    def getPopulation(self):
        return self._population

    def setArea(self,area):
        self._area = area

    def getArea(self):
        return self._area

    def popDensity(self):
        return self._population / self._area

main()

It creates the Nationdict.dat file but it just contains these 5 characters €}”.

Can you please tell me what am I doing wrong? I've been over this so many times and looked through tons of articles, help sites, etc, and can't figure out what I'm missing.

Appreciate it!

Jes

Answer 1

You are not doing anything wrong, pickle generates a file that is not human readable. To check if it works run another program

import pickle
import so # so.py is my name of the file with your code from the question
print(pickle.load(open( "nationdict.dat", "rb")))