import re
s = 'ADD 3 -11'.split()

r = re.compile(r'-?d')
for i in range(len(s)):
    try:
        if r.search(s[i]):
            s[i] = int(s[i])
    except ValueError:
        pass
print(s)

>>> s = 'STRING 3 -11 +2 3.14 0xFF 00101100'.split()
>>> s
['STRING', '3', '-11', '+2', '3.14', '0xFF', '00101100']
>>> for i in range(len(s)):
...   try:
...     s[i] = int(s[i])
...   except ValueError:
...     pass
...
>>> s
['STRING', 3, -11, 2, '3.14', '0xFF', 101100]