二分法python实现

def bin_search(list,item):
 low=0
 high=len(list)-1
 while low<=high: #4
 mid = round(((low + high) / 2)+0.1,0) #1
 #mid=(low + high) / 2
 guess=list[int(mid)]
 if guess==item:
 return int(mid)
 if guess>item:
 high=mid-1 #2
 else:
 low=mid+1 #3
 return None

my_list=[1,3,5,7,9]
print(bin_search(my_list,7))

注意二分法的思想，实现中四处标记的原理，以及第四处加等号和不加等号的影响