Is it a eight bit signed number?

Implement String.eightBitSignedNumber(), which should return True if given object is a number representable by 8 bit signed integer (-128 to -1 or 0 to 127), false/False otherwise.

It should only accept numbers in canonical representation, so no leading +, extra 0s, spaces etc.

signed_eight_bit_number = lambda number: number in map(str, xrange(-128,128))

Where the map function,

map(f, iterable) is basically equivalent to: [f(x) for x in iterable].

map on its own can't do a Cartesian product, because the length of its output list is always the same as its input list. You can trivially do a Cartesian product with a list comprehension though:

[(a, b) for a in iterable_a for b in iterable_b]

The syntax is a little confusing -- that's basically equivalent to:

result = []
for a in iterable_a:
    for b in iterable_b:
        result.append((a, b))

Regular Expression

import re
SIGNED_BYTE_PATTERN = re.compile(r'''
    \A
    (?:
        0 |
        -? (?:
            1 (?:
                [01] \d? |
                2 [0-7]? |
                [3-9] )? |
            [2-9] \d? ) |
        -128 )
    \Z
''', re.X)


def signed_eight_bit_number(number):
    return bool(SIGNED_BYTE_PATTERN.search(number))