如何在 Pandas DataFrame 中分组计数值
要按值计分组,可以使用 Pandas DataFrame 的 groupby()、size() 和 unstack() 方法。首先,创建一个带有 3 列的 DataFrame -
dataFrame = pd.DataFrame({ 'Product Category': ['Computer', 'Mobile Phone', 'Electronics', 'Electronics', 'Computer', 'Mobile Phone'],'Product Name': ['Keyboard', 'Charger', 'SmartTV', 'Camera', 'Graphic Card', 'Earphone'],'Quantity': [10, 50, 10, 20, 25, 50]})
现在,使用 groupby() 方法按值计分组。要计数,可以使用 size() 和 unstack()。unstack() 提供了一个新的列标签层 -
dataFrame = dataFrame.groupby(['Product Category', 'Product Name', 'Quantity']).size().unstack(fill_value=0)
示例
以下是完整代码 -
import pandas as pd # create a dataframe with 3 columns dataFrame = pd.DataFrame({ 'Product Category': ['Computer', 'Mobile Phone', 'Electronics', 'Electronics', 'Computer', 'Mobile Phone'],'Product Name': ['Keyboard', 'Charger', 'SmartTV', 'Camera', 'Graphic Card', 'Earphone'],'Quantity': [10, 50, 10, 20, 25, 50]}) # dataframe print"Dataframe...\n",dataFrame # count and unstack dataFrame = dataFrame.groupby(['Product Category', 'Product Name', 'Quantity']).size().unstack(fill_value=0) print"\nResultant DataFrame...\n",dataFrame
输出
这会产生以下输出 -
Dataframe... Product Category Product Name Quantity 0 Computer Keyboard 10 1 Mobile Phone Charger 50 2 Electronics SmartTV 10 3 Electronics Camera 20 4 Computer Graphic Card 25 5 Mobile Phone Earphone 50 Resultant DataFrame... Quantity 10 20 25 50 Product Category Product Name Computer Graphic Card 0 0 1 0 Keyboard 1 0 0 0 Electronics Camera 0 1 0 0 SmartTV 1 0 0 0 Mobile Phone Charger 0 0 0 1 Earphone 0 0 0 1
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