假设我们有如下代码片段:
from collections import namedtuple, Counter
Experiment = namedtuple('Experiment', ['day', 'distribution'])
LabResults = namedtuple('LabResults', ['lab_name', 'experiments_data'])
lab_results_list_good = [
LabResults(
'Lab A',
[
Experiment('first_day', Counter('abc')),
Experiment('second_day', Counter(''))
],
),
LabResults(
'Lab B',
[
Experiment('first_day', Counter('')),
Experiment('second_day', Counter('a')),
]
)
]
lab_results_list_bad = [
LabResults(
'Lab A',
[
Experiment('first_day', Counter('abc')),
Experiment('second_day', Counter('def'))
],
),
LabResults(
'Lab B',
[
Experiment('first_day', Counter('ghi')),
]
)
]
def merge_distributions(lab_results_list):
day_to_distribution_report = Counter()
for lab_result in lab_results_list:
curr_day_to_dist = Counter({exp.day: exp.distribution for exp in lab_result.experiments_data})
day_to_distribution_report += curr_day_to_dist
return day_to_distribution_report
第一种情况很好,第二种情况不起作用:
In [2]: print merge_distributions(lab_results_list_good)
Counter({'first_day': Counter({'a': 1, 'c': 1, 'b': 1}), 'second_day': Counter({'a': 1})})
In [3]: print merge_distributions(lab_results_list_bad)
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-3-969bd085f2e5> in <module>()
----> 1 print merge_distributions(lab_results_list_bad)
<ipython-input-1-0bdc39e8c846> in merge_distributions(lab_results_list)
42
43 curr_day_to_dist = Counter({exp.day: exp.distribution for exp in lab_result.experiments_data})
---> 44 day_to_distribution_report += curr_day_to_dist
45 return day_to_distribution_report
/usr/local/Cellar/python/2.7.13/Frameworks/Python.framework/Versions/2.7/lib/python2.7/collections.pyc in __add__(self, other)
642 result = Counter()
643 for elem, count in self.items():
--> 644 newcount = count + other[elem]
645 if newcount > 0:
646 result[elem] = newcount
TypeError: unsupported operand type(s) for +: 'Counter' and 'int'
在Python2中,这不只是第二种情况,在Python3中,这两种情况都不起作用。你知道吗
所以我的问题是,当python3无法运行这两种情况时,合并计数器计数器是一个非常糟糕的主意?这看起来像是一个错误,因为计数器对象支持添加。你知道吗
编辑我找到合并分布函数的快速修复方法:
def merge_distributions(lab_results_list):
day_range = {exp.day for lab_result in lab_results_list for exp in lab_result.experiments_data}
day_to_distribution_report = Counter()
for lab_result in lab_results_list:
curr_day_to_dist = Counter({exp.day: exp.distribution for exp in lab_result.experiments_data})
map(lambda day: curr_day_to_dist.setdefault(day, Counter()), day_range)
day_to_distribution_report += curr_day_to_dist
return day_to_distribution_report
为什么python源代码在默认情况下不这样做?你知道吗
如果计数器没有属性,则默认为
0
,而不是Counter()
下面是一个
DefaultCounter
实现:相关问题 更多 >
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