convert str(list) to list using json module

Question

I get a ValueError when loading a stringified list using str with json.loads. E.g.

l = ['a', 'b']
l_str = str(l)
l_loaded = json.loads(l_str)

However, this works:

x = '["a", "b"]'
x_loaded = json.loads(x)

Why is this?

But then why is '["a", "b"]' valid json and loadable with json.loads(x)? — morfys, Nov 27 '18 at 14:51
Because that *is* valid JSON. Specifically, JSON requires `"` quotes, not `'` quotes. — deceze, Nov 27 '18 at 14:52

score 4 · Accepted Answer · answered Nov 27 '18 at 14:58

Try printing out the value of l_str. You'll see

['a', 'b']

not the

["a", "b"]

that you're comparing it to.

And even if this happened to work, it's not a good idea to muddle formats like this. What if someone came along and gave you the list [None, object(), open("/usr/bin/python3", "r")]? That is definitely not going to be valid JSON when stringified.

score 3 · Answer 2 · answered Nov 27 '18 at 14:54

3

JSON syntax is not Python syntax. JSON requires double quotes for its strings.

answered Nov 27 '18 at 14:54

Arbazz Hussain

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score 3 · Answer 3 · answered Nov 27 '18 at 14:55

3

Because str() uses simple quotes as default, and JSON requires double quotes.

For more details about str(), see this

answered Nov 27 '18 at 14:55

TheWildHealer

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convert str(list) to list using json module

3 Answers3