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Python中使用json.load()和json.loads()加載json數(shù)據(jù)的方法實(shí)例

 更新時(shí)間:2022年08月12日 10:31:11   作者:cool?whidpers  
在python編程中,我們經(jīng)常要用到j(luò)son對(duì)象作為數(shù)據(jù)交換格式,下面這篇文章主要給大家介紹了關(guān)于Python中使用json.load()和json.loads()加載json數(shù)據(jù)的方法實(shí)例,文中通過(guò)實(shí)例代碼介紹的非常詳細(xì),需要的朋友可以參考下

前言

最近在python里面用json讀取json文件,可是老是不成功,特此記錄一下。

預(yù)備知識(shí):

def load(fp, cls=None, object_hook=None, parse_float=None,
        parse_int=None, parse_constant=None, object_pairs_hook=None, **kw):
    """Deserialize ``fp`` (a ``.read()``-supporting file-like object containing
    a JSON document) to a Python object."""


def loads(s, encoding=None, cls=None, object_hook=None, parse_float=None,
        parse_int=None, parse_constant=None, object_pairs_hook=None, **kw):
    """Deserialize ``s`` (a ``str`` instance containing a JSON
    document) to a Python object."""

其實(shí)我剛剛看json.load()和json.loads()代碼定義的時(shí)候,也不知道什么是文件類(lèi)型。什么是字符串類(lèi)型,用python的type函數(shù)看一下就好了

例如:

with open("文件名") as f:
     print(type(f))  # <class '_io.TextIOWrapper'>  也就是文本IO類(lèi)型
     result=json.load(f)

with open("文件名") as f:
    line=f.readline():  
    print(type(line))  # <class 'str'>
    result=json.loads(line)

使用方法

從以上可以看出json.load()是用來(lái)讀取文件的,即,將文件打開(kāi)然后就可以直接讀取。示例如下:

with open("文件名") as f:
     result=json.load(f)

json.loads()是用來(lái)讀取字符串的,即,可以把文件打開(kāi),用readline()讀取一行,然后json.loads()一行。示例如下:

#json文件為:
{"outputs": ["pool1/7x7/ets", "pool1/7x7/rf", "pool1/10x10/ets", "pool1/10x10/rf", "pool1/13x13/ets", "pool1/13x13/rf"]}

讀取代碼如下:

with open("文件名") as f:
    line=f.readline():
    result=json.loads(line)

當(dāng)json文件如下時(shí),讀取內(nèi)容是錯(cuò)誤的:

{
"dataset":{
    "train": {"type": "mnist", "data_set": "train", "layout_x": "tensor"},
    "test": {"type": "mnist", "data_set": "test", "layout_x": "tensor"}
},
"train":{
    "keep_model_in_mem":0,
    "random_state":0,
    "data_cache":{
        "cache_in_disk":{
            "default":1
        },
        "keep_in_mem":{
            "default":0
        },
        "cache_dir":"/mnt/raid/fengji/gcforest/mnist/fg-tree500-depth100-3folds/datas"
    }
},
"net":{
"outputs": ["pool1/7x7/ets", "pool1/7x7/rf", "pool1/10x10/ets", "pool1/10x10/rf", "pool1/13x13/ets", "pool1/13x13/rf"],
"layers":[
    {
        "type":"FGWinLayer",
        "name":"win1/7x7",
        "bottoms": ["X","y"],
        "tops":["win1/7x7/ets", "win1/7x7/rf"],
        "n_classes": 124,
        "estimators": [
            {"n_folds":3,"type":"ExtraTreesClassifier","n_estimators":500,"max_depth":100,"n_jobs":-1,"min_samples_leaf":10},
            {"n_folds":3,"type":"RandomForestClassifier","n_estimators":500,"max_depth":100,"n_jobs":-1,"min_samples_leaf":10}
        ],
        "stride_x": 2,
        "stride_y": 2,
        "win_x":7,
        "win_y":7
    },
    {
        "type":"FGWinLayer",
        "name":"win1/10x10",
        "bottoms": ["X","y"],
        "tops":["win1/10x10/ets", "win1/10x10/rf"],
        "n_classes": 10,
        "estimators": [
            {"n_folds":3,"type":"ExtraTreesClassifier","n_estimators":500,"max_depth":100,"n_jobs":-1,"min_samples_leaf":10},
            {"n_folds":3,"type":"RandomForestClassifier","n_estimators":500,"max_depth":100,"n_jobs":-1,"min_samples_leaf":10}
        ],
        "stride_x": 2,
        "stride_y": 2,
        "win_x":10,
        "win_y":10
    },
    {
        "type":"FGWinLayer",
        "name":"win1/13x13",
        "bottoms": ["X","y"],
        "tops":["win1/13x13/ets", "win1/13x13/rf"],
        "n_classes": 10,
        "estimators": [
            {"n_folds":3,"type":"ExtraTreesClassifier","n_estimators":500,"max_depth":100,"n_jobs":-1,"min_samples_leaf":10},
            {"n_folds":3,"type":"RandomForestClassifier","n_estimators":500,"max_depth":100,"n_jobs":-1,"min_samples_leaf":10}
        ],
        "stride_x": 2,
        "stride_y": 2,
        "win_x":13,
        "win_y":13
    },
    {
        "type":"FGPoolLayer",
        "name":"pool1",
        "bottoms": ["win1/7x7/ets", "win1/7x7/rf", "win1/10x10/ets", "win1/10x10/rf", "win1/13x13/ets", "win1/13x13/rf"],
        "tops": ["pool1/7x7/ets", "pool1/7x7/rf", "pool1/10x10/ets", "pool1/10x10/rf", "pool1/13x13/ets", "pool1/13x13/rf"],
        "pool_method": "avg",
        "win_x":2,
        "win_y":2
    }
]

}
}

因?yàn)樵诖a中,json.loads()并沒(méi)有讀取完整的json文件,只是讀取了行,所以這時(shí)json.loads(line)讀取的是不合符json語(yǔ)法的字符串,會(huì)報(bào)錯(cuò):

with open("文件名") as f:
    line=f.readline():   # 這里line只是讀取了json文件的一行,并沒(méi)有全部讀取,所以line里面所存的字符串是不符合json語(yǔ)法的,所以讀取出錯(cuò)。
    result=json.loads(line)

 Traceback (most recent call last):
  File "D:/PycharmProjects/mnistCheck/test.py", line 12, in <module>
    result = json.loads(row)
  File "C:\ProgramData\Anaconda3\envs\tensorflow\lib\json\__init__.py", line 319, in loads
    return _default_decoder.decode(s)
  File "C:\ProgramData\Anaconda3\envs\tensorflow\lib\json\decoder.py", line 339, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "C:\ProgramData\Anaconda3\envs\tensorflow\lib\json\decoder.py", line 355, in raw_decode
    obj, end = self.scan_once(s, idx)
json.decoder.JSONDecodeError: Expecting property name enclosed in double quotes: line 2 column 1 (char 2)

那么問(wèn)題來(lái)了。。。。在實(shí)際應(yīng)用中,我們會(huì)在json文件中做注釋?zhuān)热缫?ldquo;//”開(kāi)頭的注釋?zhuān)俗⑨尣糠滞?,其他?nèi)容都是符合json語(yǔ)法的,那么我們要怎么處理呢?

    def load_json(path):   
    import json
    lines = []     #  第一步:定義一個(gè)列表, 打開(kāi)文件
    with open(path) as f:  
        for row in f.readlines(): # 第二步:讀取文件內(nèi)容 
            if row.strip().startswith("http://"):   # 第三步:對(duì)每一行進(jìn)行過(guò)濾 
                continue
            lines.append(row)                   # 第四步:將過(guò)濾后的行添加到列表中.
    return json.loads("\n".join(lines))       #將列表中的每個(gè)字符串用某一個(gè)符號(hào)拼接為一整個(gè)字符串,用json.loads()函數(shù)加載,這樣就大功告成啦?。?/pre>

總結(jié)

到此這篇關(guān)于Pythonh中使用json.load()和json.loads()加載json數(shù)據(jù)的文章就介紹到這了,更多相關(guān)Pythonh加載json數(shù)據(jù)內(nèi)容請(qǐng)搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關(guān)文章希望大家以后多多支持腳本之家!

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