def isOdd(integer):
#assert isinstance(integer, int)
return integer % 2 == 1
def isEven(integer):
#assert isinstance(integer, int)
return integer % 2 == 0
def _list_to_string(li):
return ''.join(map(str, li))
class GrayCode(object):
def __init__(self, nbits):
self._nbits = nbits
self._grayCode = []
self.__generate()
def __getitem__(self, i):
return self._grayCode[i]
def __str__(self):
return str(self._grayCode)
__repr__ = __str__
def __iter__(self):
return self._grayCode.__iter__()
def __generate(self):
li = [0 for i in xrange(self._nbits)]
self._grayCode.append(_list_to_string(li))
for term in xrange(2, (1<<self._nbits)+1):
if isOdd(term):
for i in xrange(-1,-(self._nbits),-1):
if li[i]==1:
li[i-1]=li[i-1]^1
break
if isEven(term):
li[-1]=li[-1]^1
self._grayCode.append(_list_to_string(li))
class GrayCodeIterator(object):
def __init__(self, nbits):
self._nbits = nbits
def __iter__(self):
li = [0 for i in xrange(self._nbits)]
yield _list_to_string(li)
for term in xrange(2, (1<<self._nbits)+1):
if isOdd(term):
for i in xrange(-1,-(self._nbits),-1):
if li[i]==1:
li[i-1]=li[i-1]^1
break
if isEven(term):
li[-1]=li[-1]^1
yield _list_to_string(li)
if __name__=='__main__':
d = 4
codes=GrayCode(d)
print '%d digits gray codes:' % d
print codes
print 'Using Iterator:'
#for c in GrayCode(20):
# print c
for c in GrayCodeIterator(20):
print c
