寫給自己的技術筆記 - 作為程式開發者我們絕對不能忽略的JSON - Python 如何處理JSON文件
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如果覺得我的圖不清楚都可以直接在我的Github上看喔,Github連結
哈囉,由於JSON系列的第一篇(寫給自己的技術筆記 - 作為程式開發者我們絕對不能忽略的JSON - 教學和用法 - 以JavaScript為例(一))已經針對JSON做過介紹了,所以這篇就不會再詳細介紹JSON囉,這篇會把重點放在如何使用Python來處理JSON檔案
1. JSON 介紹
- JSON 全名為 JavaScript Object Notation,即 JavaScript 對象標記法
- 2001年提出
- 特性:
- 輕量型(Light-Weight): 表示產出的檔案非常小
- 基於文本的(Text-Based): 可以使用文本編譯器(ex. 記事本)開啟
- 可讀的(Human-Readable)格式: 可以輕鬆被人閱讀
- 穩定性(Stability): JSON創始人說 JSON 格式永遠不會改變,也就是說很久以前寫的 JSON 文件,很久以後也能使用,就不會有兼容性的問題
- 目前 REST API 的主流形式,可見它在數據交換格式的重要性
2. Python中的JSON套件
- json套件: Python中用來編碼和解碼JSON文件的套件
- json套件為Python中自帶的套件,所以不用額外安裝,只需要直接載入即可
JSON 和 Python 資料型態轉換表
Python 轉 JSON
JSON 轉 Python
3. Python 如何處理 JSON 套件
處理過程分成:
- Marshalling / Encoder 序列化: 代表將 Python 的物件資料轉換成為 JSON 物件,使用方法 - json.dumps 或 json.dump
- Unmarshalling / Decoder 反序列化: 代表將 JSON 物件轉換成為 Python 的資料物件,使用方法 - json.loads 或 json.load
使用方法
完整參數
- json.dumps
dumps(obj, *, skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, cls=None, indent=None, separators=None, default=None, sort_keys=False, **kw)
- json.dump
dump(obj, fp, *, skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, cls=None, indent=None, separators=None, default=None, sort_keys=False, **kw)
- json.loads
loads(s, *, encoding=None, cls=None, object_hook=None, parse_float=None, parse_int=None, parse_constant=None, object_pairs_hook=None, **kw)
- json.load
load(fp, *, cls=None, object_hook=None, parse_float=None, parse_int=None, parse_constant=None, object_pairs_hook=None, **kw)
4. 實作
JSON 檔案或字符串 轉 Python字典
1. 從JSON檔中導入
- 我們有一份JSON擋 - test.json
{ "Student 1": { "Student_id": 126, "Name": "Jack", "Score": 99, "Friends": ["Tim", "Jen", "Ken"] }, "Student 2": { "Student_id": 128, "Name": "Ken", "Score": 99, "Friends": ["Jack", "Jessy", "Cathy"] } }
- 方法一: json.load
import json ## 讀取JSON檔 with open('test.json', 'r') as f: ## 轉成Python Dict python_dict = json.load(fp = f) print("Python Dict: ", python_dict) print("Type: ", type(python_dict))
執行結果
Python Dict: {'Student 1': {'Student_id': 126, 'Name': 'Jack', 'Score': 99, 'Friends': ['Tim', 'Jen', 'Ken']}, 'Student 2': {'Student_id': 128, 'Name': 'Ken', 'Score': 99, 'Friends': ['Jack', 'Jessy', 'Cathy']}} Type: <class 'dict'>
- 方法二: json.loads
import json ## 讀取JSON檔 with open('test.json', 'r') as f: ## 將內容裝進text text = f.read() print("JSON Format: ", text) print("Type: ", type(text)) print("From JSON String Transform To Python Dict") print("Python Dict: ", json.loads(text)) print("Type: ", type(json.loads(text)))
執行結果
JSON Format: { "Student 1": { "Student_id": 126, "Name": "Jack", "Score": 99, "Friends": ["Tim", "Jen", "Ken"] }, "Student 2": { "Student_id": 128, "Name": "Ken", "Score": 99, "Friends": ["Jack", "Jessy", "Cathy"] } } Type: <class 'str'> From JSON String Transform To Python Dict Python Dict: {'Student 1': {'Student_id': 126, 'Name': 'Jack', 'Score': 99, 'Friends': ['Tim', 'Jen', 'Ken']}, 'Student 2': {'Student_id': 128, 'Name': 'Ken', 'Score': 99, 'Friends': ['Jack', 'Jessy', 'Cathy']}} Type: <class 'dict'>
2. 有一筆JSON Format的字符串 轉 Python Dict
- 只能使用json.loads
import json ## JSON Format的字符串 text = '{"Name":"Jack", "Score": 99}' print("JSON Format: ", text) print("Type:, "type(text)) print("From JSON String Transform To Python Dict") print("Python Dict: ", json.loads(text)) print("Type: ", type(json.loads(text)))
執行結果
JSON Format: {"Name":"Jack", "Score": 99} Type: <class 'str'> From JSON String Transform To Python Dict Python Dict: {'Name': 'Jack', 'Score': 99} Type: <class 'dict'>
Python 字典(Dict) 轉 JSON字符串
1. 寫入到JSON檔 - 會自動保存成JSON檔
- 方法一: json.dump
import json ## Python 字典 python_dict = { 'Name': "Jack", 'Score': 99 } ## 存成JSON File with open("python2json.json", 'w') as f: json.dump(python_dict, f)
- 方法二: JSON.dumps
import json ## Python 字典 python_dict = { 'Name': "Jack", "Score": 99, } print("Python Dict: ", python_dict) print("Type: ", type(python_dict)) print("From Python Dict Transform To JSON Format") print("JSON Format: ", json.dumps(python_dict)) print("Type: ", type(json.dumps(python_dict))) ## 存成JSON File with open('python2json1.json', 'w') as f: f.write(json.dumps(python_dict))
執行結果
Python Dict: {'Name': 'Jack', 'Score': 99} Type: <class 'dict'> From Python Dict Transform To JSON Format JSON Format: {"Name": "Jack", "Score": 99} Type: <class 'str'>
2. 轉成 JSON Format的字符串
- 只能使用函數: json.dumps
import json ## Python 字典 python_dict = { 'Name': "Jack", "Score": 99, } print("Python Dict: ", python_dict) print("Type: ", type(python_dict)) print("From Python Dict Transform To JSON Format") print("JSON Format: ", json.dumps(python_dict)) print("Type: ", type(json.dumps(python_dict)))
執行結果
Python Dict: {'Name': 'Jack', 'Score': 99} Type: <class 'dict'> From Python Dict Transform To JSON Format JSON Format: {"Name": "Jack", "Score": 99} Type: <class 'str'>
Python 字典(Dict)中包含list 轉 JSON 字符串
- 範例: 這邊是使用dumps來存進檔案
import json ## Python 字典 python_dict = { "Student A": { "Student_id": 126, "Name": "Jack", "Score": 99, "Friends": ["Tim", "Jen", "Cindy"] }, "Student B":{ "Student_id": 128, "Name": "Ken", "Score": 98, "Friends": ["Jack", "Jessy", "Cathy"] } } print("Python Dict: ", python_dict) print("Type: ", type(python_dict)) print("From Python Dict Transform To JSON Format") print("JSON Format: ", json.dumps(python_dict)) print("Type: ", type(json.dumps(python_dict))) ## 存成JSON File with open('python2json2.json', 'w') as f: f.write(json.dumps(python_dict))
執行結果
Python Dict: {'Student A': {'Student_id': 126, 'Name': 'Jack', 'Score': 99, 'Friends': ['Tim', 'Jen', 'Cindy']}, 'Student B': {'Student_id': 128, 'Name': 'Ken', 'Score': 98, 'Friends': ['Jack', 'Jessy', 'Cathy']}} Type: <class 'dict'> From Python Dict Transform To JSON Format JSON Format: {"Student A": {"Student_id": 126, "Name": "Jack", "Score": 99, "Friends": ["Tim", "Jen", "Cindy"]}, "Student B": {"Student_id": 128, "Name": "Ken", "Score": 98, "Friends": ["Jack", "Jessy", "Cathy"]}} Type: <class 'str'>
大家也可以試試用json.dump的方式存成JSON檔喔
5. 重要補充: 如果寫進JSON檔,想要更易讀的格式來寫
- 前面的範例中,當我們把Python Dict轉成JSON Format的字符串時,都會變成一排(行),但實際上的狀況是我們需要閱讀這些JSON檔,如果數據一多就會很難閱讀
- 在json.dumps()裡面填上一個參數indent,用來指定每行開頭要空幾格
- 範例一: 我將indent設4,代表空四格
import json ## Python 字典 python_dict = { 'Name': "Jack", "Score": 99, } print("Python Dict: ", python_dict) print("Type: ", type(python_dict)) print("From Python Dict Transform To JSON Format") print("JSON Format: ", json.dumps(python_dict)) print("Type: ", type(json.dumps(python_dict))) ## 存成JSON File with open('python2json3.json', 'w') as f: f.write(json.dumps(python_dict, indent = 4))
執行結果
Python Dict: {'Name': 'Jack', 'Score': 99} Type: <class 'dict'> From Python Dict Transform To JSON Format JSON Format: {"Name": "Jack", "Score": 99} Type: <class 'str'>
- json.dump也擁有參數indent喔
- 範例二:
import json ## Python 字典 python_dict = { "Student A": { "Student_id": 126, "Name": "Jack", "Score": 99, "Friends": ["Tim", "Jen", "Cindy"] }, "Student B":{ "Student_id": 128, "Name": "Ken", "Score": 98, "Friends": ["Jack", "Jessy", "Cathy"] } } print("Python Dict: ", python_dict) print("Type: ", type(python_dict)) print("From Python Dict Transform To JSON Format") print("JSON Format: ", json.dumps(python_dict)) print("Type: ", type(json.dumps(python_dict))) ## 存成JSON File with open('python2json4.json', 'w') as f: f.write(json.dumps(python_dict, indent = 4)) f.write('\n')
執行結果
Python Dict: {'Student A': {'Student_id': 126, 'Name': 'Jack', 'Score': 99, 'Friends': ['Tim', 'Jen', 'Cindy']}, 'Student B': {'Student_id': 128, 'Name': 'Ken', 'Score': 98, 'Friends': ['Jack', 'Jessy', 'Cathy']}} Type: <class 'dict'> From Python Dict Transform To JSON Format JSON Format: {"Student A": {"Student_id": 126, "Name": "Jack", "Score": 99, "Friends": ["Tim", "Jen", "Cindy"]}, "Student B": {"Student_id": 128, "Name": "Ken", "Score": 98, "Friends": ["Jack", "Jessy", "Cathy"]}} Type: <class 'str'>
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