关于time.sleep()在Threading中的行为

是挂起当前进程还是当前线程？为什么呢？

查看到ActivePython手册中有一句：

Not all built-in functions that may block waiting for I/O allow other threads to run. (The most popular ones (time.sleep(), file.read(), select.select()) work as expected.)

不太明白。。。

阻塞