def pretty_polynomial(polynomial):
    """
    Takes a list of coefficients (must be in ascending powers of x) and produces a 'pretty' output. 
    :param polynomial: the list of coefficients of a polynomial
    :return: a string of the polynomial in a more readable format. 
    """
    s = ''
    for i in range(1, len(polynomial)):
        if polynomial[i] > 0:
            s += ' + ' + str(polynomial[i]) + 'x^' + str(i)
        elif polynomial[i] < 0:
            s += '  ' + str(polynomial[i]) + 'x^' + str(i)

    # If the constant is nonzero, prepend it to the string. Otherwise, get rid of the '+'.
    if polynomial[0]:
        s = str(polynomial[0]) + s
    else:
        s = s[2:]
    return s