将对象放入列表到字典中

Question

I'm trying to create a Google Ngram-esque program in Python (CS-I project). I have a CSV file that looks like this:

aardvark, 2007, 123948
aardvark, 2008, 120423
aardvark, 2004, 96323
gorilla, 2010, 120302
gorilla, 2008, 89323
raptorjesus, 1996, 214

The first value represents the word, the second the year we're counting the number of occurrences in, and the third the number of occurrences.

I have a class CountByYear that takes in word, year, and frequency and returns a CountByYear object.

I need to read through the CSV file and print a dictionary containing the words as keys with lists of CountByYear objects as values (without the words). For example:

{'aardvark': [CountByYear(year=2007, count=123948), CountByYear(year=2008...etc.], 'gorilla: [CountByYear(year=2010, count=120302), etc...)]

I'm stuck on how I'm actually supposed to get the year and count for each object. Right now I'm doing:

for line in f:
    splitLine = line.strip().split(',')
    words[splitLine[0]] = countList
print(words)

which prints {aardvark': [], 'gorilla': [], 'raptorjesus': [] and this is good because at least I know I'm doing the dictionary part properly. But how do I fill those empty lists with the data I want?

Answer 1

You don't include the example of the CountByYear class but you specify it has a constructor that takes "word", "year", and "frequency".

Assuming a definition like this:

class CountByYear(object):
    def __init__(self, word, year, frequency):
        self.word = word
        self.year = year
        self.frequency = frequency

    def __repr__(self):
        return "CountByYear(year=%s, count=%s)" % (self.year, self.frequency)

You can do something like this:

words = {}
for line in f:
    word,year,freq = [i.strip() for i in line.split(',')]
    #create a new list if one does not already exist for this word
    if not words.get(word):
        words[word] = []
    #add this CountByYear object to corresponding list in the dictionary
    words[word].append(CountByYear(word,year,freq))
print(words)

The output from the above code on your example input file would be:

{'gorilla': [CountByYear(year=2010, count=120302), CountByYear(year=2008, count=89323)], 'aardvark': [CountByYear(year=2007, count=123948), CountByYear(year=2008, count=120423), CountByYear(year=2004, count=96323)], 'raptorjesus': [CountByYear(year=1996, count=214)]}

Answer 2

One way would be using defaultdict . For example,

from collections import defaultdict

words = defaultdict(list)

with open("data.csv", "r") as f:
    for line in f.readlines():
        key_name, year, count = line.rstrip().split(',')
        words[key_name] += [year, count]
        # or  words[key_name] += CountByYear(year, count) or similar

print(words)   

Answer 3

Try the csv module ( https://docs.python.org/3.4/library/csv.html ) and something like

import csv

words = {}
with open('eggs.csv', newline='') as csvfile:
    reader = csv.reader(csvfile, delimiter=' ', quotechar='|')

    for word, year, count in reader:
        words[word] = words.get(word, []) + [CountByYear(word, year, count)]

print(words)