如何使用python更新json文件

Question

我試圖更新現有的Json文件，但由於某種原因，所請求的值沒有被更改，但整個值（使用新值）正被追加到原始文件

jsonFile = open("replayScript.json", "r+") 
data = json.load(jsonFile) 


tmp = data["location"] 
data["location"] = "NewPath" 

jsonFile.write(json.dumps(data)) 

，其結果是： 要求：

{ 
    "location": "NewPath", 
    "Id": "0", 
    "resultDir": "", 
    "resultFile": "", 
    "mode": "replay", 
    "className": "", 
    "method": "METHOD" 
} 

實際：

{ 
"location": "/home/karim/storm/project/storm/devqa/default.xml", 
"Id": "0", 
"resultDir": "", 
"resultFile": "", 
"mode": "replay", 
"className": "", 
"method": "METHOD" 
} 
{ 
    "resultDir": "", 
    "location": "pathaaaaaaaaaaaaaaaaaaaaaaaaa", 
    "method": "METHOD", 
    "className": "", 
    "mode": "replay", 
    "Id": "0", 
    "resultFile": "" 
} 

Answer 1

def updateJsonFile(): 
    jsonFile = open("replayScript.json", "r") # Open the JSON file for reading 
    data = json.load(jsonFile) # Read the JSON into the buffer 
    jsonFile.close() # Close the JSON file 

    ## Working with buffered content 
    tmp = data["location"] 
    data["location"] = path 
    data["mode"] = "replay" 

    ## Save our changes to JSON file 
    jsonFile = open("replayScript.json", "w+") 
    jsonFile.write(json.dumps(data)) 
    jsonFile.close() 

Answer 2

這裏的問題是，您打開了一個文件並讀取其內容，因此光標位於文件的末尾。通過寫入相同的文件句柄，你基本上追加到文件。

最簡單的解決方法是在讀入文件後關閉文件，然後重新打開文件進行寫入。

with open("replayScript.json", "r") as jsonFile: 
    data = json.load(jsonFile) 

tmp = data["location"] 
data["location"] = "NewPath" 

with open("replayScript.json", "w") as jsonFile: 
    json.dump(data, jsonFile) 

或者，你可以使用seek()將光標移動迴文件的開頭，然後開始寫，然後是truncate()處理其中新數據比以前小的情況下。

with open("replayScript.json", "r+") as jsonFile: 
    data = json.load(jsonFile) 

    tmp = data["location"] 
    data["location"] = "NewPath" 

    jsonFile.seek(0) # rewind 
    json.dump(data, jsonFile) 
    jsonFile.truncate()