如何使用python更新json文件 [英] How to update json file with python

问题描述

我正在尝试更新现有的Json文件，但是由于某种原因，请求的值没有更改，但是整个值集(带有新值)都被附加到原始文件中

I'm trying to update existing Json file, but from some reason, the requested value is not being changed but the entire set of values (with the new value) is being appended to the original file

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


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

jsonFile.write(json.dumps(data))

，结果是: 必填:

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

实际:

{
"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": ""
}

推荐答案

此处的问题是您已经打开了一个文件并读取了它的内容，因此光标位于文件的末尾.通过写入相同的文件句柄，实际上是在追加文件.

The issue here is that you've opened a file and read its contents so the cursor is at the end of the file. By writing to the same file handle, you're essentially appending to the file.

最简单的解决方案是在读入文件后将其关闭，然后重新打开以进行写入.

The easiest solution would be to close the file after you've read it in, then reopen it for writing.

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，您可以使用 seek() 将光标移回文件的开头，然后开始写入，然后跟随

Alternatively, you can use seek() to move the cursor back to the beginning of the file then start writing, followed by a truncate() to deal with the case where the new data is smaller than the previous.

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()

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