PythonでJSON形式のデータを読み取る

目的

PythonでJSON形式のデータを読み取る処理の一例を記す。

読み取るJSONデータ

.json

{
	"lunches" : [
		{
			"drink": "Green Tea",
			"dessert": "Vanilla Icecream",
			"foods": [
				{
					"name": "Rice",
					"item": []
				},
				{
					"name" : "Curry",
					"item" : ["Chiken", "Onion", "Carrot"]
				},
				{
					"name": "Omelette",
					"item": ["Egg", "Butter", "Cheese"]
				}
			]
		},
		{
			"drink": "Ice Coffee",
			"dessert": "Chocolate Cake",
			"foods": [
				{
					"name": "Bread",
					"item": []
				},
				{
					"name": "Bamburger",
					"item": ["Beef", "Onion", "Egg"]
				},
				{
					"name": "Salad",
					"item": ["Lettuce", "Cucumber", "Tomato"]
				}
			]
		}
	]
}

実行結果

-----    
Green Tea
Vanilla Icecream
Rice
Curry
  Chiken        
  Onion
  Carrot        
Omelette        
  Egg
  Butter        
  Cheese        
-----
Ice Coffee      
Chocolate Cake  
Bread
Bamburger
  Beef
  Onion
  Egg
Salad
  Lettuce
  Cucumber
  Tomato

処理するPythonソースコード

.py

import sys
import json
import collections

def main(args):
	menu_file = args[1]
	menu = getMenu(menu_file)


def getMenu(menu_file=''):
	'''
	ファイル名を受け取りJSONオブジェクトを返す
	エラー発生時はNone返す

	Parameters
	----------
	menu_file : string
		メニューファイル名
	Returns
	-------
	menu : Any
		メニュー
	'''
	try:
		with open(menu_file, 'r') as food:
			try:
				decoder = json.JSONDecoder(object_pairs_hook=collections.OrderedDict)
				menu = decoder.decode(food.read())
			except json.JSONDecodeError as e:
				print('catch error : ', e)
	except FileNotFoundError as e:
		print('catch error : ', e)
	except IOError as e:
		print('catch error : ', e)

	try:
		for lunch in menu['lunches']:
			print('-----')
			print(lunch['drink'])
			print(lunch['dessert'])
			for food in lunch['foods']:
				print(food['name'])
				for food_item in food['item']:
					print(' ', food_item)
	except KeyError as e:
		menu = None
		print('catch error : ', e)
	except TypeError as e:
		menu = None
		print('catch error : ', e)

	return menu

if __name__ == "__main__":
	main(sys.argv)