class Solution(object):

def isConvex(self, points):

"""

:type points: List[List[int]]

:rtype: bool

"""

#print "points = ", points

```
numPoints = len(points)
#print "numPoints = ", numPoints
pre, cur = 0, 0
for idx in range(numPoints):
#print "idx = ", idx, " points[idx] = ", points[idx]
dx1 = points[(idx+1)%numPoints][0] - points[idx][0]
dy1 = points[(idx+1)%numPoints][1] - points[idx][1]
dx2 = points[(idx+2)%numPoints][0] - points[idx][0]
dy2 = points[(idx+2)%numPoints][1] - points[idx][1]
#print "dx1 = ", dx1, " dy1 = ", dy1
#print "dx2 = ", dx2, " dy2 = ", dy2
cur = dx1*dy2 - dx2 * dy1
#print "cur = ", cur
if cur != 0:
if cur*pre < 0:
return False
else:
pre = cur
return True
```