You can use literal_eval in the ast module

>>> from ast import literal_eval
>>> s = "['a',['b','c','d'],'e']"
>>> print(literal_eval(s))
['a', ['b', 'c', 'd'], 'e']

For the normal arrays, use ast.literal_eval:

>>> from ast import literal_eval
>>> x = "[1,2,3,4]"
>>> literal_eval(x)
[1, 2, 3, 4]
>>> type(literal_eval(x))
<type 'list'>
>>>

numpy.array's though are a little tricky because of how Python renders them as strings:

>>> import numpy as np
>>> x = [[1,2,3], [4,5,6]]
>>> x = np.array(x)
>>> x
array([[1, 2, 3],
       [4, 5, 6]])
>>> x = str(x)
>>> x
'[[1 2 3]\n [4 5 6]]'
>>>

One hack you could use though for simple ones is replacing the whitespace with commas using re.sub:

>>> import re
>>> x = re.sub("\s+", ",", x)
>>> x
'[[1,2,3],[4,5,6]]'
>>>

Then, you can use ast.literal_eval and turn it back into a numpy.array:

>>> x = literal_eval(x)
>>> np.array(x)
array([[1, 2, 3],
       [4, 5, 6]])
>>>

There's always everybody's old favourite ast.literal_eval

>>> import ast
>>> x = "[1,'Hello',['test','3'],True,2.532]"
>>> y = ast.literal_eval(x)
>>> y
[1, 'Hello', ['test', '3'], True, 2.532]
>>> z = str(y)
>>> z
"[1, 'Hello', ['test', '3'], True, 2.532]"

Use int which converts a string to an int, inside a list comprehension, like this:

desired_array = [int(numeric_string) for numeric_string in current_array]

import array as arr
output = arr.array('b', [ord(c) for c in 'abcdef'])

will output

array('b', [97, 98, 100, 101, 102])

Of course, you have to remember to convert back to characters with chr(), whenever you need to use them as letters/strings.

For 1D arrays, Numpy has a function called fromstring, so it can be done very efficiently without extra libraries.

Briefly you can parse your string like this:

s = '[0 1 2 3]'
a = np.fromstring(s[1:-1], dtype=np.int, sep=' ')
print(a) # [0 1 2 3]

For nD arrays, one can use .replace() to remove the brackets and .reshape() to reshape to desired shape, or use Merlin's solution.