如何迭代直到最长的迭代用尽.使用zip_longest进行迭代 [英] How to iterate until longest iterable is exhausted. Using zip_longest to iterate

问题描述

我正在尝试使用 itertools.zip_longest 继续进行迭代，直到用尽最长的可迭代项(而不是像常规zip那样最短).我还需要将其传递给字典.但是，我仍然缺少价值观.我应该有大约1,300个值，但只能得到560个值.我想念什么或做错什么了?

import csv
from itertools import zip_longest

my_csv = 'my_csv_file' + '.csv'

some_list = []
another_list = []
my_dictionary = {}

with open(my_csv, newline='') as f:
    reader = csv.reader(f)
    next(reader, None)
    for row in reader:
        some_list.append(row[0])
        another_list.append(row[1:])

my_dictionary = dict(zip_longest(some_list, another_list, fillvalue=None))

for v in my_dictionary.keys():
    print(v)

count = len(my_dictionary.keys())
print(str(count) + " keys")

解决方案

听起来好像有重复值的键，它们将折叠为最新值(例如:{1: 'a', 2: 'b', 1: 'c'}将折叠为{1: 'c', 2: 'b'}). /p>

您可能想使用list作为值:

from collections import defaultdict

# Set-up...

my_dictionary = defaultdict(list)
for key, value in zip_longest(some_list, another_list, fillvalue=None)
    my_dictionary[key].append(value)

for v in my_dictionary.keys():
    print(v)

keys = len(my_dictionary)
values = sum(len(value) for value in my_dictionary.itervalues())
print(str(keys) + " keys, " + str(values) +  " values")

I'm trying to use itertools.zip_longest to continue to iterate until the longest iterable is exhausted (instead of the shortest as regular zip does). I also need to pass this into a dictionary. However, I'm still missing values. I should have about 1,300 values but only getting about 560. What am I missing or doing wrong?

import csv
from itertools import zip_longest

my_csv = 'my_csv_file' + '.csv'

some_list = []
another_list = []
my_dictionary = {}

with open(my_csv, newline='') as f:
    reader = csv.reader(f)
    next(reader, None)
    for row in reader:
        some_list.append(row[0])
        another_list.append(row[1:])

my_dictionary = dict(zip_longest(some_list, another_list, fillvalue=None))

for v in my_dictionary.keys():
    print(v)

count = len(my_dictionary.keys())
print(str(count) + " keys")

解决方案

It sounds like there are keys with duplicate values, which will collapse to the most recent value (e.g.: {1: 'a', 2: 'b', 1: 'c'} would collapse to {1: 'c', 2: 'b'}).

You might want to use list as values instead:

from collections import defaultdict

# Set-up...

my_dictionary = defaultdict(list)
for key, value in zip_longest(some_list, another_list, fillvalue=None)
    my_dictionary[key].append(value)

for v in my_dictionary.keys():
    print(v)

keys = len(my_dictionary)
values = sum(len(value) for value in my_dictionary.itervalues())
print(str(keys) + " keys, " + str(values) +  " values")

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