Python，避免丑陋的嵌套for循环

Question

我是 python 编程新手。我已经尝试了很多方法来避免这些嵌套的 for 循环，但没有成功。

我的数据输入如下：

[
  {
    "province_id": "1",
    "name": "HCM",
    "districts": [
      {
        "district_id": "1",
        "name": "Thu Duc",
        "wards": [
          {
            "ward_id": "1",
            "name": "Linh Trung"
          },
          {
            "ward_id": "2",
            "name": "Linh Chieu"
          }
        ]
      },
      {
        "district_id": "2",
        "name": "Quan 9",
        "wards": [
          {
            "ward_id": "3",
            "name": "Hiep Phu"
          },
          {
            "ward_id": "4",
            "name": "Long Binh"
          }
        ]
      }
    ]
  },
  {
    "province_id": "2",
    "name": "Binh Duong",
    "districts": [
      {
        "district_id": "3",
        "name": "Di An",
        "wards": [
          {
            "ward_id": "5",
            "name": "Dong Hoa"
          },
          {
            "ward_id": "6",
            "name": "Di An"
          }
        ]
      },
      {
        "district_id": "4",
        "name": "Thu Dau Mot",
        "wards": [
          {
            "ward_id": "7",
            "name": "Hiep Thanh"
          },
          {
            "ward_id": "8",
            "name": "Hiep An"
          }
        ]
      }
    ]
  }
]

我的代码是：

for province in data:
    for district in province['districts']:
        for ward in district['wards']:
            # Excute my function
            print('{}, {}, {}'.format(ward['name'], district['name'], province['name']))

输出

Linh Trung, Thu Duc, HCM
Linh Chieu, Thu Duc, HCM
Hiep Phu, Quan 9, HCM
...

尽管我的代码可以正常工作，但它看起来很丑陋。
如何避免这些嵌套的 for 循环？

Answer 1

这里是单行本

[
    print("{}, {}, {}".format(ward["name"], district["name"], province["name"]))
    for province in data
    for district in province["districts"]
    for ward in district["wards"]
]

Answer 2

您的数据结构自然是嵌套的，但是您可以通过编写一个生成器函数来整理代码来迭代它：

def all_wards(data):
    for province in data:
        for district in province['districts']:
            for ward in district['wards']:
                yield province, district, ward

此函数中有与当前相同的三重嵌套循环，但在代码的其他任何地方，您现在都可以使用单个非嵌套循环迭代数据结构：

for province, district, ward in all_wards(data):
    print('{}, {}, {}'.format(ward['name'], district['name'], province['name']))

如果您希望避免缩进太多，这里有一种等效的方法来编写函数，类似于@adarian 的回答，但没有创建临时列表：

def all_wards(data):
    return (
        province, district, ward
        for province in data
        for district in province['districts']
        for ward in district['wards']
    )

Answer 3

你可以这样做：

def print_district(district, province):
    for ward in district['wards']:
        print('{}, {}, {}'.format(ward['name'], district['name'], province['name']))

def print_province(province):
    for district in province['districts']:
        print_district(district, province)

for province in data:   
    print_province(province)

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