如何實現一個選擇類似功能

Question

我在python有一個數據集，它的結構是這樣

Tree Species number of trunks 
------------------------------ 
Acer rubrum   1 
Quercus bicolor  1 
Quercus bicolor  1 
aabbccdd    0 

，我有一個問題，我可以實現類似的功能，

Select sum(number of trunks) 
from trees.data['Number of Trunks'] 
where x = trees.data["Tree Species"] 
group by trees.data["Tree Species"] 

在python中？ x是一個數組包含五個要素：

x = array(['Acer rubrum', 'Acer saccharum', 'Acer saccharinum', 
'Quercus rubra', 'Quercus bicolor'], dtype='<U16') 

我想要做的是在映射每個X元素trees.data [「樹種」]和計算中繼數的總和，它應該返回一個數組的

array = (sum_num(Acer rubrum), sum_num(Acer saccharum), sum_num(Acer saccharinum), 
sum_num(Acer Quercus rubra), sum_num(Quercus bicolor)) 

Answer 1

你想看看Python熊貓。這將允許你這樣做

df.groupby('Tree Species')['Number of Trunks'].sum() 

請注意這裏df是無論你在你的數據幀中讀出的變量名。我建議你看熊貓和lambda函數。

Answer 2

你可以做這樣的事情：

import pandas as pd 
df = pd.DataFrame() 
tree_species = ["Acer rubrum", "Quercus bicolor", "Quercus bicolor", "aabbccdd"] 
no_of_trunks = [1,1,1,0] 
df["Tree Species"] = tree_species 
df["Number of Trunks"] = no_of_trunks 
df.groupby('Tree Species').sum() #This will create a pandas dataframe 
df.groupby('Tree Species')['Number of Trunks'].sum() #This will create a pandas series. 

您可以通過只使用字典也做同樣的事情：

tree_species = ["Acer rubrum", "Quercus bicolor", "Quercus bicolor", "aabbccdd"] 
no_of_trunks = [1,1,1,0]  
d = {} 
for key, trunk in zip(tree_species, no_of_trunks): 
    if not key in d.keys(): 
     d[key] = 0 
    d[key] += trunk   
print(d)