Python: Taking a nested list as input?

Question

What is the best way to go about the following?

I want to let a user input a nested list as follows:

grid = input(\'Enter grid\')

The

Answer 1

As inspectorG4dget commented, use ast.literal_eval:

>>> import ast
>>> ast.literal_eval("[['', 'X', 'O'], ['X', 'O', ''], ['X', '', 'X']]")
[['', 'X', 'O'], ['X', 'O', ''], ['X', '', 'X']]

To filter out invalid input, catch SyntaxError:

>>> ast.literal_eval("[['', 'X', 'O'], ['X', 'O', ''], ['X', ', 'X']]")
Traceback (most recent call last):
  File "", line 1, in 
  File "/usr/lib/python3.4/ast.py", line 46, in literal_eval
    node_or_string = parse(node_or_string, mode='eval')
  File "/usr/lib/python3.4/ast.py", line 35, in parse
    return compile(source, filename, mode, PyCF_ONLY_AST)
  File "", line 1
    [['', 'X', 'O'], ['X', 'O', ''], ['X', ', 'X']]
                                               ^
SyntaxError: invalid syntax