[英]How do I sort a zipped list in Python?
What's the Pythonic way to sort a zipped list?对压缩列表进行排序的 Pythonic 方式是什么?
code :代码 :
names = list('datx')
vals = reversed(list(xrange(len(names))))
zipped = zip(names, vals)
print zipped
The code above prints [('d', 3), ('a', 2), ('t', 1), ('x', 0)]上面的代码打印[('d', 3), ('a', 2), ('t', 1), ('x', 0)]
I want to sort zipped by the values.我想作为排序依据的值压缩。 So ideally it would end up looking like this [('x', 0), ('t', 1), ('a', 2), ('d', 3)] .
所以理想情况下,它最终看起来像这样[('x', 0), ('t', 1), ('a', 2), ('d', 3)] 。
非常简单:
sorted(zipped, key=lambda x: x[1])
sorted(zipped, key = lambda t: t[1])
import operator
sorted(zipped, key=operator.itemgetter(1))
If you want it a little bit more faster, do ig = operator.itemgetter(1)
and use ig
as key function.如果您希望它更快一点,请执行
ig = operator.itemgetter(1)
并使用ig
作为关键函数。
In your case you don't need to sort at all because you just want an enumerated reversed list of your names
:在您的情况下,您根本不需要排序,因为您只需要一个枚举的倒序
names
列表:
>>> list(enumerate(names[::-1])) # reverse by slicing
[(0, 'x'), (1, 't'), (2, 'a'), (3, 'd')]
>>> list(enumerate(reversed(names))) # but reversed is also possible
[(0, 'x'), (1, 't'), (2, 'a'), (3, 'd')]
But if you need to sort it then you should use sorted
(as provided by @utdemir or @Ulrich Dangel) because it will work on Python2 ( zip
and itertools.zip
) and Python3 ( zip
) and won't fail with an AttributeError
like .sort(...)
(which only works on Python2 zip
because there zip
returns a list
):但是,如果您需要对其进行排序,那么您应该使用
sorted
(由 @utdemir 或 @Ulrich Dangel 提供),因为它可以在 Python2( zip
和itertools.zip
)和 Python3 ( zip
)上运行,并且不会因AttributeError
而失败.sort(...)
(仅适用于 Python2 zip
因为zip
返回一个list
):
>>> # Fails with Python 3's zip:
>>> zipped = zip(names, vals)
>>> zipped.sort(lambda x: x[1])
AttributeError: 'zip' object has no attribute 'sort'
>>> # Fails with Python 2's itertools izip:
>>> from itertools import izip
>>> zipped = izip(names, vals)
>>> zipped.sort(lambda x: x[1])
AttributeError: 'itertools.izip' object has no attribute 'sort'
But sorted
does work in each case:但
sorted
在每种情况下都有效:
>>> zipped = izip(names, vals)
>>> sorted(zipped, key=lambda x: x[1])
[('x', 0), ('t', 1), ('a', 2), ('d', 3)]
>>> zipped = zip(names, vals) # python 3
>>> sorted(zipped, key=lambda x: x[1])
[('x', 0), ('t', 1), ('a', 2), ('d', 3)]
It's simpler and more efficient to zip them in order in the first place (if you can).首先(如果可以)按顺序压缩它们更简单,更有效。 Given your example it's pretty easy:
鉴于您的示例,这很容易:
>>> names = 'datx'
>>> zip(reversed(names), xrange(len(names)))
<<< [('x', 0), ('t', 1), ('a', 2), ('d', 3)]
Sort feature importance in a classifier (dtc=decision_tree):在分类器中对特征重要性进行排序 (dtc=decision_tree):
for name, importance in sorted(zip(X_train.columns,
dtc.feature_importances_),key=lambda x: x[1]):
print(name, importance)
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