import csv

# CSV
with open("input.csv", mode="r", encoding="utf-8") as f:
    for row in csv.reader(f):
        print(row)

"""
['pref', 'population', 'area']
['aomori', '1184531', '9645.10']
['akita', '913556', '11637.52']
['iwate', '1163024', '15275.04']
['yamagata', '1026228', '9323.15']
['miyagi', '2263552', '7282.29']
['fukushima', '1766358', '13784.39']
"""

# DictReader
with open("input.csv", mode="r", encoding="utf-8") as f:
    for row in csv.DictReader(f):
        print(row)

"""
{'pref': 'aomori', 'population': '1184531', 'area': '9645.10'}
{'pref': 'akita', 'population': '913556', 'area': '11637.52'}
{'pref': 'iwate', 'population': '1163024', 'area': '15275.04'}
{'pref': 'yamagata', 'population': '1026228', 'area': '9323.15'}
{'pref': 'miyagi', 'population': '2263552', 'area': '7282.29'}
{'pref': 'fukushima', 'population': '1766358', 'area': '13784.39'}
"""

# DictWriter
data = [
    {"pref": "Aichi", "population": 7480897, "area": 5173.19},
    {"pref": "Mie", "population": 1727503, "area": 5774.48},
    {"pref": "Gifu", "population": 1929669, "area": 10621.29}
]

with open("output.csv", newline="", mode="w", encoding="utf-8") as f:
    names = ["pref", "population", "area"]
    writer = csv.DictWriter(f, fieldnames=names)
    writer.writeheader()
    writer.writerows(data)

import json

# Encode
data_dic = {
    "tokai": [
        {"pref": "aichi", "population": 100, "area": 100},
        {"pref": "mie", "population": 200, "area": 100},
        {"pref": "gifu", "population": 300, "area": 100}
    ],
    "tohoku": [
        {"pref": "aomori", "population": 100, "area": 100},
        {"pref": "akita", "population": 200, "area": 100},
        {"pref": "iwate", "population": 300, "area": 100},
        {"pref": "yamagata", "population": 400, "area": 100},
        {"pref": "miyagi", "population": 500, "area": 100},
        {"pref": "fukushima", "population": 600, "area": 100}
    ]
}
print(json.dumps(data_dic, indent=2))

"""
{
  "tokai": [
    {
      "pref": "aichi",
      "population": 100,
      "area": 100
    },
    ...
  ],
  "tohoku": [
    {
      "pref": "aomori",
      "population": 100,
      "area": 100
    },
    ...
  ]
}
"""

# Decode
data_str = ('{'
'"tokai":[{"pref":"aichi", "population":100, "area":100}],'
'"tohoku":[{"pref":"aomori", "population":100, "area":100}]'
'}')
print(json.loads(data_str))

# Read file -> Write file
with open("./input.json", mode="r") as i:
    data_str = json.load(i)
    with open("./output.json", mode="w") as o:
        json.dump(data_str, o, indent=4)