python 7 days

7days

数据类型的补充

1，元组

tu1 = ("laonanhai")
tu2 = ("laonanhai")
print(tu1,type(tu1))
print(tu2,type(tu2))

tu1 = (1)
tu2 = (1,)
print(tu1,type(tu1))
print(tu2,type(tu2))

tu1 = ([1,2,3]) 
tu2 = ([1,2,3],) 
print(tu1,type(tu1))
print(tu2,type(tu2))

list

l1 = [111,222,333,444,555]

索引为奇数对应的所有元素全部删除。

方法一：

del l1[1::2]

print(l1) 

在循坏一个列表时，最好不要改变列表的大小，会影响你的最终结果。

倒着删除

l1  = [111,222,333,444,555,]
for i in range(len(l1)-1,-1,-1):
if in % 2 == 1:
del l1[i]
print(l1)

dict

dic = dict.fronmkeys("abc",666)
print(dic)
dic = dict.fromkeys([11,22,33],666)
print(dic)
dic = dict.fromkeys([11,22,33],[])
print(dic)

l1 = []
for key in dic:
if "k" in key :
l1.append(key)
print(l1)
for key in l1:
del dic[key]
print(dic)

在循坏dict中，最好不要改变dict的大小，会影响结果或者报错。

数据类型的转换：

str ---> list split

list --->str join

tupple --->list

tu1 = (1,2,3)
l1 = list(tu1)
print(l1)
tu2 = tuple（l1）
print(tu2)

列表的去重

l1 = [11,11,22,33,33,44,[1,2,3,4]]
l2 = list (set(l1))
12.sort()
print(l2)

增：2种方法add 和update

set1.add("太白")
print(set1)
set.update("abc")
set1.update([111,222,333])
print(set1)

删：4种方法remove、pop、clear和del

remove按元素删除
set1.remove("alex")
print(set1)
随机删除，有返回值pop
print(set1.pop())
print(set1)

清空clear
set1.clear()
print(set1)
删除整体 del
del set1
print(set1)

查：一种方法for循坏

无序元素

set1 = {"alex","wusir","barry"}
for i in set1:
print(set1)

交集：

&   和   intersetion

set1 = {1,2,3,4,5}
set2 = {4,5,6,7,8}
print(set1 & set2)
print(set3)

intersetion

print(set1.intersetion(set2))

并集：

set1 = {1,2,3,4,5}
set2 = {4,5,6,7,8}
|   和  union
print(set1 | set2)
print(set1.union(set2))

　　

差集：

set1 = {1,2,3,4,5}
set2 = {4,5,6,7,8}
print(set1 - set2)  set 1 独有
print（set2.difference(set1)） set 1 独有

反交集：

set1 = {1,2,3,4,5}
set2 = {4,5,6,7,8}
print(set1 ^ set2)
print(set1.symmetric_difference(set2))

子集：

set1 = {1,2,3,}
set2 = {1,2,3,4,5,6}
print(set1 <  set2)  True  set1  是 set2 的子集
print(set1.issubset  (set2))  True  set1  是 set2 的子集

超集：

set1 = {1,2,3,}
set2 = {1,2,3,4,5,6}
print(set2  >  set1)  True  set2  是 set1 的超集
print(set2.issubset  (set1))  True  set2  是 set1 的超集

冻集合：

set1 = frozenset({1,2,3,"alex"})
print(set1,type(set1))

l1 = [1,2,3]
l2 = l1
l2.append(666)
print(l1,l2)

对于赋值运算来说，指向的都是同一个内存地址，一变都变。

浅copy：

l1 = [11,22,33]
l2 = l1.copy()
l1.append(666)
print(l1,id(l1))
print(l2,id(l2))

对于浅copy来说，第一层创建的是新的内存地址，而从第二层开始，指向的都是同一个内存地址，所以，对于第二层以及更深的层数来说，保持

深copy：

import copy
l1 = [11,22,["barry"]]
l2 = copy.deepcopy(l1)
l1[2].append("alex")
print(l1,id(l1[-1]))
print(l2,id(l2[-1]))
深copy 完全独立

l1 = [1,2,3]
l2 = [1,2,3]
l1.append(666)
print(l1,l2)

深copy，两个内存地址

对于切片来说，这是浅copy

l1 = [1,2,3,4,5,6,[11,22]]
l2 = l1[:]
l1.append(666)
print(l1.l2)
l1[-1].appemd(666)
print(l1,l2)