二分查找法python代码

以下是二分查找法的Python代码：

def binary_search(alist, item):
    first = 0
    last = len(alist)-1
    found = False

    while first<=last and not found:
        midpoint = (first + last)//2
        if alist[midpoint] == item:
            found = True
        else:
            if item < alist[midpoint]:
                last = midpoint-1
            else:
                first = midpoint+1

    return found

注意：以上代码仅供参考，实际使用时可能需要根据具体情况进行修改。