Anybody solve this problem by Python? My python codes always got the trouble:

```
def combine(n, k):
if n==0:
return []
elif k==0:
return []
elif n<k:
return []
else:
combine_list=[]
def recursive_help(n, k, sub_list, start):
if len(sub_list)==k:
print(sub_list)
combine_list.append(sub_list)
return
print(combine_list)
elif start<=n:
for i in range(start, n+1):
sub_list+=[i]
recursive_help(n, k, sub_list, i+1)
sub_list.pop()
recursive_help(n, k, [], 1)
return combine_list
```