How to convert a decimal base (10) to a negabinary base (-2)?

def neg2dec(arr):
    n = 0
    for i, num in enumerate(arr[::-1]):
        n+= ((-2)**i)*num
    return n

def dec2neg(num):
    if num == 0:
        digits = ['0']
    else:
        digits = []
        while num != 0:
            num, remainder = divmod(num, -2)
            if remainder < 0:
                num, remainder = num + 1, remainder + 2
            digits.append(str(remainder))
    return ''.join(digits[::-1])

The algorithm is described in http://en.wikipedia.org/wiki/Negative_base#Calculation. Basically, you just pick the remainder as the positive base case and make sure the remainder is nonnegative and minimal.

 7 = -3*-2 + 1  (least significant digit)
-3 =  2*-2 + 1
 2 = -1*-2 + 0
-1 =  1*-2 + 1
 1 =  0*-2 + 1  (most significant digit)