python 中为了提高字符串的使用用效率和节约内存,对于由 字母.数字.下划线组成的标识符采用了 intern 机制,即对于短字符串,将其赋值给多个对象时,内存中只有一个副本,多个对象共享这个副本.长字符串不适用. 注:驻留机制发生在编译阶段,不是运行阶段. 例: >>> a = ' >>> b = ' >>> a is b True >>> a = '-abc' >>> b = '-abc' >>&g
1.字符串intern机制 用了这么久的python,时刻和字符串打交道,直到遇到下面的情况: a = "hello" b = "hello" print(a is b) #--->True print(a == b) #---> True a = "hello world" b = "hello world" print(a is b) # ---> False print(a == b) # --->
Incomputer science, string interning is a method of storing only onecopy of each distinct string value, which must be immutable. Interning strings makes some stringprocessing tasks more time- or space-efficient at the cost of requiring moretime when
变量的存储 a = 'abc' 理解:①先在内存中生成一个字符串‘abc’ ②可以把比变量名a看做一个便利贴,然后将a贴到‘abc’中 ③注意顺序,是生成‘abc’,然后再创建a指向‘abc’ python的is 和==的区别 is用来判断两个对象的ID是否一样 a = [1,3,4,5] b = [1,3,4,5] print(a == b) print(a is b) True False 上述代码中之所以a == b成立,是因为a是一个list类型,list类型中实现了魔法函数__
static PyStringObject *characters[UCHAR_MAX + 1]; ... /* This dictionary holds all interned strings. Note that references to strings in this dictionary are *not* counted in the string's ob_refcnt. When the interned string reaches a refcnt of 0 the st
Python3 字符串 Python字符串运算符 + 字符串连接 a + b 输出结果: HelloPython * 重复输出字符串 a*2 输出结果:HelloHello [] 通过索引获取字符串中字符 a[1] 输出结果 e [ : ] 截取字符串中的一部分,取到截止点的前一个 a[1:4] 输出结果 ell in 成员运算符 - 如果字符串中包含给定的字符返回 True H in a 输出结果 1 not in 成员运算符 - 如果字符串中不包含给定的字符返回 True M not in
