前言
最近在python里面用json读取json文件，可是老是不成功，特此记录一下。
预备知识：
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."""
其实我刚刚看json.load()和json.loads()代码定义的时候，也不知道什么是文件类型。什么是字符串类型，用python的type函数看一下就好了
例如：
with open("文件名") as f:
print(type(f)) # 也就是文本IO类型
result=json.load(f)
with open("文件名") as f:
line=f.readline():
print(type(line)) #
result=json.loads(line)
使用方法
从以上可以看出json.load()是用来读取文件的，即，将文件打开然后就可以直接读取。示例如下：
with open("文件名") as f:
result=json.load(f)
json.loads()是用来读取字符串的，即，可以把文件打开，用readline()读取一行，然后json.loads()一行。示例如下：
#json文件为：
{"outputs": ["pool1/7x7/ets", "pool1/7x7/rf", "pool1/10x10/ets", "pool1/10x10/rf", "pool1/13x13/ets", "pool1/13x13/rf"]}
读取代码如下：
with open("文件名") as f:
line=f.readline():
result=json.loads(line)
当json文件如下时，读取内容是错误的：
{
"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
}
]
}
}
因为在代码中，json.loads()并没有读取完整的json文件，只是读取了行，所以这时json.loads(line)读取的是不合符json语法的字符串，会报错：
with open("文件名") as f:
line=f.readline(): # 这里line只是读取了json文件的一行，并没有全部读取，所以line里面所存的字符串是不符合json语法的，所以读取出错。
result=json.loads(line)
Traceback (most recent call last):
File "D:/PycharmProjects/mnistCheck/test.py", line 12, in
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)
那么问题来了。。。。在实际应用中，我们会在json文件中做注释，比如以“//”开头的注释，除了注释部分外，其他内容都是符合json语法的，那么我们要怎么处理呢？
def load_json(path):
import json
lines = [] # 第一步：定义一个列表， 打开文件
with open(path) as f:
for row in f.readlines(): # 第二步：读取文件内容
if row.strip().startswith("//"): # 第三步：对每一行进行过滤
continue
lines.append(row) # 第四步：将过滤后的行添加到列表中.
return json.loads("\n".join(lines)) #将列表中的每个字符串用某一个符号拼接为一整个字符串，用json.loads()函数加载，这样就大功告成啦！！
总结
到此这篇关于Pythonh中使用json.load()和json.loads()加载json数据的文章就介绍到这了,更多相关Pythonh加载json数据内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家！