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var = 520 print(type(var)) # <class 'int'>
float(浮点型):
var = 5.20 print(type(var)) # 输出:<class 'float'>
bool(布尔型):
var = true print(type(var)) # 输出:<class 'bool'>
complex(复数):
var = complex(13,14) print(type(var)) # 输出:<class 'complex'>
(2)String(字符串)
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var = “pig” print(type(var)) # 输出:<class 'str'> print(var[0:3]) # 正向访问,输出:'pig' print(var[-1]) # 反向访问,输出:'g'
(3)List(列表)
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var = [ 'pig' , 1 , 2.2 ] print(type(var)) # 输出:<class 'list'> print(var[0]) # 获得第一个元素,输出:'pig' print(var+var) # 打印组合的列表,输出:[ 'pig', 1 , 2.2,'pig', 1 , 2.2 ]
(4)Tuple(元组)
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var = ( 'pig', 1 , 2.2 ) print(type(var)) # 输出:<class 'tuple'> print(var[0]) # 获得第一个元素,输出:'pig' print(var+var) # 打印组合的元组,输出:( 'pig', 1 , 2.2,'pig', 1 , 2.2 ) var[0] = 'dog' # 出错!不能被二次赋值
(5)Dictionary(字典)
"{ }"标识,字典由索引key和它对应的值value组成。
dic = {'name':'张三','age':18} print(dic ['name']) # 得到键为'name' 的值,输出:'张三' print(dic [age]) # 得到键为'age' 的值,输出:18 print(dic) # 得到完整的字典,输出:{'name':'张三','age':18} print(dic.keys()) # 得到所有键,输出:dict_keys:(['name','age']) print(dic.values()) # 输出所有值,输出:dict_values:(['张三',18])
二、python变量的存储
1、变量与储存地址的关系
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#include<iostream> using namespace std; int main() { int test = 1; cout << &test << ":" << test << endl; test = 2; cout << &test << ":" << test << endl; return 0; }
运行结果:
0020FDC8:1
0020FDC8:2
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str = 'girls are pig' print(id(str)) str = 'boys are dog' print(id(str))
运行结果:
113811696
113812464
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list1 = [1,2,3] print(list1) #输出:[1,2,3] print(id(list1)) #输出:112607104(不同电脑分配给变量的地址不同) list1[0] = "hello" print(list1) #输出:['hello',2,3] print(id(list1)) #输出:112607104 list1.append(4) print(list1) #输出:['hello',2,3,4] print(id(list1)) #输出:112607104 list1 = ['hello',4] print(list1) #输出:['hello',4] print(id(list1)) #输出:112925120
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list1 = ['hello',2,3,4] print(id(list1[0])) #输出:112926064 print(id(list1[3])) #输出:8791404644096 list2 = ['hello',4] print(id(list2[0])) #输出:112926064 print(id(list2[1])) #输出:8791404644096
3、变量的赋值——浅拷贝和深拷贝
(1)变量赋值的安全隐患
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list1 = [1,2,3] list2 = list1 print(list1) #输出:[1,2,3] print(list2) #输出:[1,2,3] print(id(list1)) #输出:112607104 print(id(list2)) #输出:112607104 list1[0] = 'hello' print(list1) #输出:['hello',2,3] print(list2) #输出:['hello',2,3] print(id(list1)) #输出:112607104 print(id(list2)) #输出:112607104
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import copy people = ['girl','boy'] list1 = [1,2,people] list2 = copy.copy(list1) print(list1) #输出:[1,2,['girl','boy']] print(list2) #输出:[1,2,['girl','boy']] list1.append('hello') list2.append('hi') print(list1) #输出:[1,2,['girl','boy'],'hello'] print(list2) #输出:[1,2,['girl','boy'],'hi'] people[0] = 'pig' print(list1) #输出:[1,2,['pig','boy'],'hello'] print(list2) #输出:[1,2,['pig','boy'],'hi']
(3)深拷贝
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import copy people = ['girl','boy'] list1 = [1,2,people] list2 = copy.deepcopy(list1) print(list1) #输出:[1,2,['girl','boy']] print(list2) #输出:[1,2,['girl','boy']] list1.append('hello') list2.append('hi') print(list1) #输出:[1,2,['girl','boy'],'hello'] print(list2) #输出:[1,2,['girl','boy'],'hi'] people[0] = 'pig' print(list1) #输出:[1,2,['pig','boy'],'hello'] print(list2) #输出:[1,2,['girl','boy'],'hi']
三、python变量数据类型的大小
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import sys print(sys.getsizeof(0)) # 输出:24 print(sys.getsizeof(1)) # 输出:28 print(sys.getsizeof(2)) # 输出:28 print(sys.getsizeof(2**15)) # 输出:28 print(sys.getsizeof(2**30)) # 输出:32 print(sys.getsizeof(2**128)) # 输出:44
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struct PyLongObject { long ob_refcnt; // 8 bytes struct _typeobject *ob_type; // 8 bytes long ob_size; // 8 bytes unsigned int ob_digit[1]; // 4 bytes * abs(ob_size) };
"htmlcode">
struct PyLongObject { int ob_refcnt; // 4 bytes struct _typeobject *ob_type; // 4 bytes int ob_size; // 4 bytes unsigned short ob_digit[1]; // 2 bytes * abs(ob_size) };
"1" color="#000000" />
Tips:本人能力有限,如有错误之处麻烦指出。放弃不难,但坚持一定很酷!
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