class Solution(object):

def numberOfArithmeticSlices(self, A):

"""

:type A: List[int]

:rtype: int

"""

```
#1st
def helper(B, e): #judge whether array B , plus a new element, constructing an arithmetic slice
#print ('B: ',B, e)
if (B[-2] - B[-1] == B[-1] - e):
return True
else:
return False
count = 0
for i in range(0, len(A)):
j = i + 2
while j < len(A):
if helper(A[i:j], A[j]):
count += 1
j += 1
else:
break
return count
```