def binary_search(list, item):
    low = 0 #最低位索引位置为0
    high = len(list)- 1 #最高位索引位置为总长度-1
    while low <= high: 
        mid = (low + high)//2 #检查中间的元素，书上是一条斜杠，我试过加两条斜杠才行
        guess = list[mid]#python自动圆整
        if guess == item:  #找到了元素
            return mid
        if guess > item:  #猜的数字大了,就修改high
            high = mid - 1
        else:            #猜的数字小了,就修改low
            low = mid + 1
    return None   #没有指定的元素

>>> if __name__ == "__main__":#我试过加上好用
	 my_list=[1,3,5,7,9]
	 print (binary_search(my_list,3))#把binary_search也加上括号

	 
1#表示3的索引位置为1
>>> if __name__ == "__main__":
	 my_list=[1,3,5,7,9]
	 print (binary_search(my_list,0))

	 
None#表示0不在列表中

def findSmallest(arr):
    smallest = arr[0] 
    smallest_index =0
    for i in range(1,len(arr)):
        if arr[i] < smallest:
            smallest = arr[i]
            smallest_index= i
    return smallest_index

def selectionSort(arr):
    newArr = []
    for i in range(len(arr)):
        smallest = findSmallest(arr)
        newArr.append(arr.pop(smallest))  
    return newArr

#样式1，把selcetionSort()作为新的值给arr,打印arr
>>> number=[5,3,6,2,10]
>>> arr=selectionSort(number)
>>> arr
[2, 3, 5, 6, 10]
#样式2,加上if __name__ == '__main__':（我也不知道啥作用）
>>> if __name__ == '__main__':
	number=[5,3,6,2,10]
	print(selectionSort(number))

	
[2, 3, 5, 6, 10]
#样式3，直接输出，最简洁
>>> number=[5,3,6,2,10]
>>> print(selectionSort(number))
[2, 3, 5, 6, 10]