[英]Python 3 efficiently iterating over a dictionary of list
I have working code that classifies data based on rules inside a dictionary of list. 我有工作代码,根据列表字典中的规则对数据进行分类。 I want to know if it is possible to make the code more efficient by getting rid of the nested for loops using list/dictionary comprehensions or .values().
我想知道是否可以通过使用list / dictionary comprehensions或.values()删除嵌套的for循环来提高代码的效率。
import pandas as pd
df=pd.DataFrame({'Animals': [ 'Python', 'Anaconda', 'Viper', 'Cardinal',
'Trout', 'Robin', 'Bass', 'Salmon', 'Turkey', 'Chicken'],
'Noise': ['Hiss','SSS','Hisss','Chirp','Splash','Chirp',
'Gulp','Splash','Gobble','Cluck'],
})
snakenoise =['Hiss','SSS','Hisss', 'Wissss', 'tseee']
birdnoise =['Chirp', 'squeak', 'Cluck', 'Gobble']
fishnoise =['Splash', 'Gulp', 'Swim']
AnimalDex = {'Snake':['0', 'slither',snakenoise],
'Bird':['2','fly', birdnoise],
'Fish':['0','swim',fishnoise],
}
df['movement'] = ''
for key, value in AnimalDex.items():
for i in range(len(AnimalDex[key][2])):
df.loc[df.Noise.str.contains(AnimalDex[key][2][i]),'movement'] = AnimalDex[key][1]
print (df)
Here is the output 这是输出
Animals Noise movement
0 Python Hiss slither
1 Anaconda SSS slither
2 Viper Hisss slither
3 Cardinal Chirp fly
4 Trout Splash swim
5 Robin Chirp fly
6 Bass Gulp swim
7 Salmon Splash swim
8 Turkey Gobble fly
9 Chicken Cluck fly
If you just use the values instead of the keys and indexes, you can really simplify your loop. 如果您只使用值而不是键和索引,则可以真正简化循环。
for animal in AnimalDex.values():
for value in animal[2]:
df.loc[df.Noise.str.contains(value),'movement'] = animal[1]
Efficiency does not come from rewriting loops as comprehensions, since comprehensions mainly provide a nicer syntax for loops. 效率不是来自重写循环作为理解,因为理解主要为循环提供更好的语法。 Rather, it's the efficiency of the data structure lookups that is important.
相反,重要的是数据结构查找的效率。 The problem is that
df.Noise.str.contains(AnimalDex[key][2][i])
performs brute-force matching. 问题是
df.Noise.str.contains(AnimalDex[key][2][i])
执行强力匹配。
If your goal is to merge the movements defined in AnimalDex
into the df
, joining according to the noise, then it pays to build a dictionary that maps noises to movements: 如果您的目标是将
AnimalDex
定义的移动合并到df
,根据噪声加入,那么构建将噪声映射到移动的字典是值得的:
noise_to_movement = {}
for order in AnimalDex.values():
for noise in order[2]:
noise_to_movement[noise] = order[1]
For comparison, here is another way to construct noise_to_movement
, using incomprehensible comprehensions: 为了比较,这是使用难以理解的理解来构造
noise_to_movement
另一种方法:
import itertools
noise_to_movement = dict(itertools.chain(*[list(
itertools.product(order[2], [order[1]])) for order in AnimalDex.values()
]))
Either way, once the dictionary is built, setting the 'movement'
column becomes a trivial lookup: 无论哪种方式,一旦构建了字典,设置
'movement'
列就变成了一个简单的查找:
df['movement'] = list(noise_to_movement[n] for n in df.Noise)
To really improve performance you shouldn't be iterating through a dictionary at all. 要真正提高性能,你根本不应该遍历字典。 Instead make a
pandas.DataFrame
out of that data, and join the two DataFrames. 而是从该数据中创建一个
pandas.DataFrame
,并加入两个DataFrame。
import pandas as pd
df = pd.DataFrame({'Animals': [ 'Python', 'Anaconda', 'Viper', 'Cardinal',
'Trout', 'Robin', 'Bass', 'Salmon', 'Turkey', 'Chicken'],
'Noise': ['Hiss','SSS','Hisss','Chirp','Splash','Chirp',
'Gulp','Splash','Gobble','Cluck']})
snakenoise =['Hiss','SSS','Hisss', 'Wissss', 'tseee']
birdnoise =['Chirp', 'squeak', 'Cluck', 'Gobble']
fishnoise =['Splash', 'Gulp', 'Swim']
noises = [(snakenoise, 'Snake', '0', 'slither'),
(birdnoise, 'Bird', '2', 'fly'),
(fishnoise, 'Fish', '0', 'swim')]
animal_dex = {'Animal Type': [],
'Whatever': [],
'Movement': [],
'Noise': []}
for noise in noises:
animal_dex['Noise'] += noise[0]
animal_dex['Animal Type'] += map(lambda x: noise[1], noise[0])
animal_dex['Whatever'] += map(lambda x: noise[2], noise[0])
animal_dex['Movement'] += map(lambda x: noise[3], noise[0])
df1 = pd.DataFrame(animal_dex)
df = df.merge(df1, on='Noise')
df
Animals Noise Animal Type Movement Whatever
0 Python Hiss Snake slither 0
1 Anaconda SSS Snake slither 0
2 Viper Hisss Snake slither 0
3 Cardinal Chirp Bird fly 2
4 Robin Chirp Bird fly 2
5 Trout Splash Fish swim 0
6 Salmon Splash Fish swim 0
7 Bass Gulp Fish swim 0
8 Turkey Gobble Bird fly 2
9 Chicken Cluck Bird fly 2
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