谁会用python写个二分法查找的循环？？？我都展开了，因为不会写一起。。。谢谢

def half_seek(point, seqence):
    a = len(readsx)
    b = a/2
    if point <= readsx[b]:
c = readsx[:b + 1]
a = len(c)
b = a/2
    if point <= c[b]:
c = c[:b + 1]
a = len(c)
b = a/2
else:
c = c[b:]
a = len(c)
b = a/2
    if point <= c[b]:
c = c[:b + 1]
a = len(c)
b = a/2
    else: 
    c = c[b:]
    a = len(c)
b = a/2
    if point <= c[b]:
else:
c = readsx[b:]
a = len(c)
b = a/2
if point <= c[b]:
c = c[:b + 1]
a = len(c)
b = a/2
else:
c = c[b:]
a = len(c)
b = a/2
if point <= c[b]:
c = c[:b + 1]
a = len(c)
b = a/2

格式不对。。。。。我就不粘贴了。。。。怎么写个循环呢？
我是想写个函数以后用，目的是给一个值，给了一个由小到大的数列list形式，确定这个给的数能排哪个位置？

让它执行8次，最后return个列表形式的小区间也行（因为我一直都是切片下来的）。关键是不会写循环

http://blog.csdn.net/buaa_shang/article/details/8280564