Python 的「groupby」方法如何有效地將物件陣列中的資料分組和聚合？

使用GroupBy 方法將數組中的物件分組

Python 強大的groupby 方法可以根據選定的屬性對物件進行高效分組。如果您需要執行此類分組操作，groupby 提供了一個方便的解決方案。

例如，考慮以下物件陣列：

[ 
    { Phase: "Phase 1", Step: "Step 1", Task: "Task 1", Value: "5" },
    { Phase: "Phase 1", Step: "Step 1", Task: "Task 2", Value: "10" },
    { Phase: "Phase 1", Step: "Step 2", Task: "Task 1", Value: "15" },
    { Phase: "Phase 1", Step: "Step 2", Task: "Task 2", Value: "20" },
    { Phase: "Phase 2", Step: "Step 1", Task: "Task 1", Value: "25" },
    { Phase: "Phase 2", Step: "Step 1", Task: "Task 2", Value: "30" },
    { Phase: "Phase 2", Step: "Step 2", Task: "Task 1", Value: "35" },
    { Phase: "Phase 2", Step: "Step 2", Task: "Task 2", Value: "40" }
]

按 Phase將物件分組並計算總和值，我們使用：

from itertools import groupby

def sum_value(objects):
    return sum(int(obj["Value"]) for obj in objects)

objects.sort(key=lambda obj: obj["Phase"])
grouped_by_phase = groupby(objects, key=lambda obj: obj["Phase"])

result = [{
    "Phase": phase,
    "Value": sum_value(objects)
} for phase, objects in grouped_by_phase]

print(result)

這會產生所需的輸出：

[{"Phase": "Phase 1", "Value": 50}, {"Phase": "Phase 2", "Value": 130}]

或者，要按階段和步驟進行分組，我們可以使用多個層級的分組：

grouped_by_phase_and_step = groupby(objects, key=lambda obj: (obj["Phase"], obj["Step"]))

result = [{
    "Phase": phase,
    "Step": step,
    "Value": sum_value(objects)
} for (phase, step), objects in grouped_by_phase_and_step]

print(result)

這將返回：

[{"Phase": "Phase 1", "Step": "Step 1", "Value": 15}, {"Phase": "Phase 1", "Step": "Step 2", "Value": 35}, {"Phase": "Phase 2", "Step": "Step 1", "Value": 55}, {"Phase": "Phase 2", "Step": "Step 2", "Value": 75}]

借助Python多功能的groupby方法，您可以輕鬆有效地對物件數組中的資料進行分組和聚合，滿足您的各種分組需求。

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