[Python源码剖析]获取Python小整数集合范围

#!/usr/bin/env python
#-*- coding=utf-8 -*-
 
small_ints = dict()
for i in range(-10000,10000):
    small_ints[i] = id(i)
 
for i in range(-10000,10000):
    if id(i) != small_ints[i]:
        del small_ints[i]
 
print("[%s, %s]"%(min(small_ints.keys()), max(small_ints.keys())))

　　在默认的官方下载的安装程序Python2.7 和Python3.6结果一样都是

[-5, 256]

　　Python源码Objects/intobject.c]中64-75行是

#ifndef NSMALLPOSINTS
#define NSMALLPOSINTS		257
#endif
#ifndef NSMALLNEGINTS
#define NSMALLNEGINTS		5
#endif
#if NSMALLNEGINTS + NSMALLPOSINTS > 0
/* References to small integers are saved in this array so that they
   can be shared.
   The integers that are saved are those in the range
   -NSMALLNEGINTS (inclusive) to NSMALLPOSINTS (not inclusive).
*/

　　默认设定为[-5,257), 需要改源码编译安装才能自定义这个小整数集合. Python是用对象池技术实现的. 具体继续看书了...