Convert string representation of list to list


Question

I was wondering what the simplest way is to convert a string list like the following to a list:

x = u'[ "A","B","C" , " D"]'

Even in case user puts spaces in between the commas, and spaces inside of the quotes. I need to handle that as well to:

x = ["A", "B", "C", "D"] 

in Python.

I know I can strip spaces with strip() and split() using the split operator and check for non alphabets. But the code was getting very kludgy. Is there a quick function that I'm not aware of?

1
438
3/21/2018 4:36:20 PM

Accepted Answer

>>> import ast
>>> x = u'[ "A","B","C" , " D"]'
>>> x = ast.literal_eval(x)
>>> x
['A', 'B', 'C', ' D']
>>> x = [n.strip() for n in x]
>>> x
['A', 'B', 'C', 'D']

ast.literal_eval:

With ast.literal_eval, you can safely evaluate an expression node or a string containing a Python expression. The string or node provided may only consist of the following Python literal structures: strings, numbers, tuples, lists, dicts, booleans, and None.

638
2/27/2018 9:10:37 AM

The eval is dangerous - you shouldn't execute user input.

If you have 2.6 or newer, use ast instead of eval:

>>> import ast
>>> ast.literal_eval('["A","B" ,"C" ," D"]')
["A", "B", "C", " D"]

Once you have that, strip the strings.

If you're on an older version of Python, you can get very close to what you want with a simple regular expression:

>>> x='[  "A",  " B", "C","D "]'
>>> re.findall(r'"\s*([^"]*?)\s*"', x)
['A', 'B', 'C', 'D']

This isn't as good as the ast solution, for example it doesn't correctly handle escaped quotes in strings. But it's simple, doesn't involve a dangerous eval, and might be good enough for your purpose if you're on an older Python without ast.


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