python json dumps與loads有可能犯的錯誤

json.dumps() 是將一個Python數據結構轉換為一個JSON編碼的字符串

json.loads() 是將一個JSON編碼的字符串轉換為一個Python數據結構

 

 

如下：

>>> import json

>>> a={'name':'xiaoming'}

>>> json.dumps(a)

'{"name": "xiaoming"}'

>>> b='{"name": "xiaoming"}'

>>> json.loads(b)

{u'name': u'xiaoming'}

 

 

注意：我們原先定義a的元素都是用單引號，而dumps轉化后都變成了雙引號，而在loads后變成python變量時，元素都變成了單引號，並且字符串前加多了個u。

 

那么當我定義如下的字符串類型時，元素內容用單引號，而整個字符串用雙引號括起來：

>>> c="{'name':'xiaoming'}"

>>> print json.loads(c)

Traceback (most recent call last):

File "<stdin>", line 1, in <module>

File "/usr/local/python27/lib/python2.7/json/__init__.py", line 339, in loads

return _default_decoder.decode(s)

File "/usr/local/python27/lib/python2.7/json/decoder.py", line 364, in decode

obj, end = self.raw_decode(s, idx=_w(s, 0).end())

File "/usr/local/python27/lib/python2.7/json/decoder.py", line 380, in raw_decode

obj, end = self.scan_once(s, idx)

ValueError: Expecting property name: line 1 column 2 (char 1)

 

程序報錯了，所以 一般要求當要字符串通過loads轉為python數據類型時，得外層用單引號，里面元素key和value用雙引號

 

還有，即使滿足上述條件，當有u前綴的unicode出現修飾時，也會報錯：

>>> c='{u"name": u"xiaoming"}'

>>> json.loads(c)

Traceback (most recent call last):

File "<stdin>", line 1, in <module>

File "/usr/local/python27/lib/python2.7/json/__init__.py", line 339, in loads

return _default_decoder.decode(s)

File "/usr/local/python27/lib/python2.7/json/decoder.py", line 364, in decode

obj, end = self.raw_decode(s, idx=_w(s, 0).end())

File "/usr/local/python27/lib/python2.7/json/decoder.py", line 380, in raw_decode

obj, end = self.scan_once(s, idx)

ValueError: Expecting property name: line 1 column 2 (char 1)

 

所以loads在處理中，還需要把里面的u前綴修飾符去掉

 

 

 

 

 https://stackoverflow.com/questions/25707558/json-valueerror-expecting-property-name-line-1-column-2-char-1

 

 

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