Float identity - V2EX
V2EX = way to explore
V2EX 是一个关于分享和探索的地方
现在注册
已注册用户请  登录
推荐学习书目
Learn Python the Hard Way
Python Sites
PyPI - Python Package Index
http://diveintopython.org/toc/index.html
Pocoo
值得关注的项目
PyPy
Celery
Jinja2
Read the Docs
gevent
pyenv
virtualenv
Stackless Python
Beautiful Soup
结巴中文分词
Green Unicorn
Sentry
Shovel
Pyflakes
pytest
Python 编程
pep8 Checker
Styles
PEP 8
Google Python Style Guide
Code Style from The Hitchhiker's Guide
damngoto
V2EX    Python

Float identity

  •  
  •   damngoto 2022-07-28 18:29:04 +08:00 2061 次点击
    这是一个创建于 1175 天前的主题,其中的信息可能已经有所发展或是发生改变。
    # Equal ai = 1 bi = 1 print(id(ai), id(bi)) # Not equal af = 1.0 bf = 1.0 print(id(af), id(bf)) # False 

    float 在 Python 里面不是 immutable 的 primitive type 吗? 为啥和 int 表现的不一样呢?

    7 条回复    2022-07-28 23:07:38 +08:00
    ClericPy
        1
    ClericPy  
       2022-07-28 18:55:06 +08:00   1
    [-5, 256] 是常驻内存的

    >>> a = -7
    >>> b = -7
    >>> a is b
    False
    damngoto
        2
    damngoto  
    OP
       2022-07-28 19:12:01 +08:00
    @ClericPy 学习了。
    想问下 string 的表现该怎么解释呢?
    ClericPy
        3
    ClericPy  
       2022-07-28 20:04:36 +08:00
    @damngoto 没懂, 那些常驻内存的东西就是默认情况下赋值就直接从内存里拿来用, 不会重新申请内存. 字符串是重新申请内存的
    ccvzz
        4
    ccvzz  
       2022-07-28 20:29:21 +08:00   1
    filwaline
        5
    filwaline  
       2022-07-28 21:01:56 +08:00 via Android   2
    https://github.com/satwikkansal/wtfpython

    新 P 友看看 wtf-python 吧,各种奇怪特性包罗万象嘿嘿嘿
    damngoto
        6
    damngoto  
    OP
       2022-07-28 23:04:45 +08:00 via Android
    @ClericPy 但是两个值一样的字符串 identity 是一样的。
    damngoto
        7
    damngoto  
    OP
       2022-07-28 23:07:38 +08:00 via Android
    @ccvzz @filwaline 看来我跳进了一个大坑。。。
    关于     帮助文档     自助推广系统     博客     API     FAQ     Solana     5809 人在线   最高记录 6679       Select Language
    创意工作者们的社区
    World is powered by solitude
    VERSION: 3.9.8.5 22ms UTC 01:47 PVG 09:47 LAX 18:47 JFK 21:47
    Do have faith in what you're doing.
    ubao msn snddm index pchome yahoo rakuten mypaper meadowduck bidyahoo youbao zxmzxm asda bnvcg cvbfg dfscv mmhjk xxddc yybgb zznbn ccubao uaitu acv GXCV ET GDG YH FG BCVB FJFH CBRE CBC GDG ET54 WRWR RWER WREW WRWER RWER SDG EW SF DSFSF fbbs ubao fhd dfg ewr dg df ewwr ewwr et ruyut utut dfg fgd gdfgt etg dfgt dfgd ert4 gd fgg wr 235 wer3 we vsdf sdf gdf ert xcv sdf rwer hfd dfg cvb rwf afb dfh jgh bmn lgh rty gfds cxv xcv xcs vdas fdf fgd cv sdf tert sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf shasha9178 shasha9178 shasha9178 shasha9178 shasha9178 liflif2 liflif2 liflif2 liflif2 liflif2 liblib3 liblib3 liblib3 liblib3 liblib3 zhazha444 zhazha444 zhazha444 zhazha444 zhazha444 dende5 dende denden denden2 denden21 fenfen9 fenf619 fen619 fenfe9 fe619 sdf sdf sdf sdf sdf zhazh90 zhazh0 zhaa50 zha90 zh590 zho zhoz zhozh zhozho zhozho2 lislis lls95 lili95 lils5 liss9 sdf0ty987 sdft876 sdft9876 sdf09876 sd0t9876 sdf0ty98 sdf0976 sdf0ty986 sdf0ty96 sdf0t76 sdf0876 df0ty98 sf0t876 sd0ty76 sdy76 sdf76 sdf0t76 sdf0ty9 sdf0ty98 sdf0ty987 sdf0ty98 sdf6676 sdf876 sd876 sd876 sdf6 sdf6 sdf9876 sdf0t sdf06 sdf0ty9776 sdf0ty9776 sdf0ty76 sdf8876 sdf0t sd6 sdf06 s688876 sd688 sdf86