Python基础数据类型补充及深浅拷贝

-*-coding:utf-8 -*-
ascii      不支持中文
gbk        支持中文   2个字节   包含ascii码
unicode    万国码     python3 内存unicode
utf-8      可变的长   英文 1 字节  欧洲2个字节  亚洲3个字节

unicode   内存
硬盘     utf-8 字节     存储  传送

s = '澳门'
a = 'alexsb'
s1 = s.encode('utf-8')   # 编码    编码集
print(s1)                  # b'xe6xbexb3xe9x97xa8'
print(s1.decode('utf-8'))
a1 = a.encode('utf-8')   #  b'alexsb'
print(a1)
s2 = s.encode('gbk')
print(s2)                  # b'xb0xc4xc3xc5'
a2 = a.encode('gbk')        # b'alexsb'
print(a2)
s3 = s.encode('utf-8')
print(s3.decode('gbk'))      # 不能使得

s = 'alex'
s1 = s.encode('utf-8')   # 编码     utf-8  包含了ascii
print(s1.decode('gbk'))  # 解码     gbk    包含了ascii

应用场景:  文件操作   网络传输   网络编程

坑   基础数据补充

li = [1,2,3,4,5,0,0,0,0,0,0,0,0,0]

for i in li:
   li.append(0)
print(li)        # [1,2,3,4,5,0,0,0,0,0]

li = [12,2,3,4,5]
for i in li:
   li.append(i)
   print(li)
print(li)


for i in li:
   li.remove(i)
print(li)   # 结果[2,4]

for i in li:
   li.pop()
print(li)



li = [1,2,3,4,5]
for i in li:
   del li[-1]
print(li)





for i in range(len(li)):      # 行
   li.pop()
print(li)

li = [1,2,3,4,5]              # 行
l2 = []
for i in li:
   l2.append(i)
for j in l2:
   li.remove(j)
print(li)

for i in li:
   li.clear()                  # 实在不行的
print(li)

dic = {'1':22,'5':'22'}
for i in dic:
   dic['6'] = 1
print(dic)

lst = []
for i in dic:
   lst.append(i)   # 每个字典的键
for j in lst:
   dic.pop(j)
print(dic)


dic = dict.fromkeys('年后啊','消愁')

第一个位置是可迭代对象,也就是字典的键
第二个位置 不写是None  也就是字典的值

print(dic)
dic['年'] = '今天老子不上班'   # 字符串不能修改
print(dic)

dic['你'] = [5,6,7]
print(dic)
dic = dict.fromkeys('你好啊',[1,2,3])
print(dic)
dic['你'].append(99)
print(dic)

深浅拷贝

li = [1,2,3,4]
lst = li.copy()
print(li)
print(lst)

print(id(li))   # 34512776
print(id(lst))  # 34512840

li[0] = 56
print(li)   # 变
print(lst)  # 不变



print(id(li[0]))  # 1548382960
print(id(lst[0])) # 1548381200

print(id(li[1]))  # 1548381232
print(id(lst[1])) # 1548381232


li = [1,2,3,4,[5,6,7]]    # 浅拷贝只拷贝一层元素
lst = li.copy()
# print(li)
# print(lst)

li[-1].append(90)
print(li)   # 变
print(lst)  # 变

print(id(li[-1]))
print(id(lst[-1]))


li = [1,2,3,4]    # 赋值
lst = li
print(li)
print(lst)

li[0] = 56
print(li)
print(lst)

import copy

li = [1,2,3,4,[5,6,7]]
lst = copy.deepcopy(li)   # 深拷贝
# 浅拷贝只拷贝第一层元素,元素是不可变的,就不会变 元素是可变的俩个同时变
print(li)
print(lst)
print(id(li))      # 40289984
print(id(lst))     # 40305368

li[-1].append(90)
print(li)   # 变
print(lst)  # 不变

print(id(li[-1]))  #38783856
print(id(lst[-1])) #38798000

import copy

li = [1,2,3,4,[5,6,7]]

lst = copy.deepcopy(li)

print(id(lst[-2]))   # 39584432
print(id(li[-2]))    # 39570288

面试题:

li = [1,2]   # li = [1,[1,[1,[1,2]]]]
li[1] = li
print(li)
 结果 [1, [...]]

is == 区别

a = 1000
b = 1000
print(a == b)
print(id(a))
print(id(b))
print(a is b)   # is 是

 ==  比较两边的值            # 看这俩人是不是长得一样
is   比较两边的内存地址      # 判断是不是一个   身份证号


代码块

def func():
   a = 'asd@fasdf'* 20
   print(id(a))
def func1():
   b = 'asd@fasdf'* 20
   print(id(b))
print(func(),func1())   

a = 100000000
b = 100000000
c = 100000000
d = 100000000

一个文件就是一个代码块:

print(a is b)   #  节省资源


代码块机制:

数字: -5 ~ 256
字符串:  乘法的时候总长度不能超过20

代码块 > 小数据

s = '222222222222222222222222222222222222222222222222222222'
f = '222222222222222222222222222222222222222222222222222222'

print(s is f)

s = 'asdsr' * -50
d = 'asdsr' * -50
print(s is d)

a = '12221341asdfadsfasxzvdasfasdfewfwfvxasgfrqegvewrgavrgvaerg'
b = '12221341asdfadsfasxzvdasfasdfewfwfvxasgfrqegvewrgavrgvaerg'

a = '@'* 2
b = '@'* 2