Given a number, how do we find the next greater number with the same digits?

nextgreaternum.py

num = raw_input()
ind = len(num)-1

while ind > 0 and num[ind] <= num[ind-1]:	
	ind -= 1

#There is no greater number with the same digits
if ind == 0:
	print "Not possible"
else:
	result = num[0:ind-1] #the left part
	
	l_digit = num[ind-1] #left digit to be swapped
	g_digit = num[ind] #candidate for digit to be swapped
	right_digits = [num[ind]]
	g_ind = ind+1

	while g_ind < len(num):
		right_digits.append(num[g_ind])
		if num[g_ind] > l_digit and num[g_ind] < g_digit:
			g_digit = num[g_ind]
		g_ind += 1

	result += g_digit
	right_digits.remove(g_digit)
	right_digits.append(l_digit)
	right_digits.sort()

	result += "".join(right_digits)
	print result