Python 条件句和itertools.groupby问题

我使用groupby解析单词列表，并根据单词的长度将它们组织到列表中。例如：

from itertools import groupby

words = ['this', 'that', 'them', 'who', 'what', 'where', 'whyfore']

for key, group in groupby(sorted(words, key = len), len):
    print key, list(group)

3 ['who']
4 ['this', 'that', 'them', 'what']
5 ['where']
7 ['whyfore']

获取列表的长度也很有效：

for key, group in groupby(sorted(words, key = len), len):
    print len(list(group))

1
4
1
1

问题是，如果我事先像这样放置一个条件，这就是结果：

for key, group in groupby(sorted(words, key = len), len):
    if len(list(group)) > 1:
        print list(group)

输出：

[]

为什么会这样

每个组都是一个iterable，把它变成一个列表会耗尽它。不能将iterable转换为列表两次

将列表存储为新变量：

for key, group in groupby(sorted(words, key = len), len):
    grouplist = list(group)
    if len(grouplist) > 1:
        print grouplist

现在，您只需使用iterable一次：

>>> for key, group in groupby(sorted(words, key = len), len):
...     grouplist = list(group)
...     if len(grouplist) > 1:
...         print grouplist
... 
['this', 'that', 'them', 'what']

每个组都是一个iterable，把它变成一个列表会让它筋疲力尽。不能将iterable转换为列表两次

将列表存储为新变量：

for key, group in groupby(sorted(words, key = len), len):
    grouplist = list(group)
    if len(grouplist) > 1:
        print grouplist

现在，您只需使用iterable一次：

>>> for key, group in groupby(sorted(words, key = len), len):
...     grouplist = list(group)
...     if len(grouplist) > 1:
...         print grouplist
... 
['this', 'that', 'them', 'what']

---

@JumBopap：仍然只迭代一次，存储结果，对其进行测试。@JumBopap：仍然只迭代一次，存储结果，对其进行测试。