# 关于元组的函数

• 以下看代码
• 以下函数，对list基本适用
``````# len：获取元组的长度
t = (1,2,3,4,5)
len(t)``````
``````5

``````
``````# max，min：最大最小值
print(max(t))
print(min(t))``````
``````5
1

``````
``````# tuple：转化或创建元组
l = (1,2,3,4,5)
t = tuple(l)
print(t)

t = tuple()
print(t)``````
``````(1, 2, 3, 4, 5)
()

``````

# 元组的函数

• 基本跟list通用
``````# count：计算指定数据出现的次数
t = (2,1,2,3,45,1,1,2,)

print(t.count(2))

# index：求指定元素在元组中的索引位置

print(t.index(45))
# 如果需要的查找的数字是多个，则返回第一个

print(t.index(1))``````
``````3
4
1

``````

# 元组变量交换法

• 两个变量交换值
``````# 两个变量交换值
a = 1
b = 3

print(a)
print(b)
print("*" * 20)
# java程序员会这么写：
c = a
a = b
b = c
print(a)
print(b)

print("*" * 20)
# python写法
a,b = b,a
print(a)
print(b)``````
``````1
3
********************
3
1
********************
1
3

``````

# 集合-set

• 集合是高中数学中的一个概念
• 一堆确定的无序的唯一的数据，集合中每一个数据成为一个元素
``````# 集合的定义
s = set()
print(type(s))
print(s)

# 此时，大括号内一定要有值，否则定义出的是一个dict
s = {1,2,3,4,5,6,7}
print(type(s))
print(s)``````
``````<class 'set'>
set()
<class 'set'>
{1, 2, 3, 4, 5, 6, 7}

``````
``````# 如果只是用大括号定义，则定义的是一个dict类型
d = {}
print(type(d))
print(d)``````
``````<class 'dict'>
{}

``````

# 集合的特征

• 集合的数据无序，即无法使用索引和分片
• 集合内部数据元素具有唯一性，可以用来排除重复数据
• 集合内的数据，str，int，float，tuple，冰冻集合等，即内部只能放置可哈希数据

# 集合序列操作

``````# 成员检测
# in，not in
s = {4,5,"i", "love", "you"}
print(s)

if "love" in s:
print("Yes")

if "haha" not in s:
print("Yes")``````
``````{'you', 4, 5, 'love', 'i'}
Yes
Yes

``````

# 集合遍历操作

``````# for 循环
s = {4,5,"i", "love", "you"}

for i in s:
print(i)``````
``````you
4
5
love
i

``````
``````# 带有元组的集合遍历
s = {(1,2,3,), ("i", "love", "you"), (4,5,6)}

for k,m,n in s:
print(k, "--", m, "--", n)

for k in s:
print(k)``````
``````i -- love -- you
4 -- 5 -- 6
1 -- 2 -- 3
('i', 'love', 'you')
(4, 5, 6)
(1, 2, 3)

``````

# 集合的内涵

``````# 普通集合内涵
# 以下集合在初始化后自动过滤掉重复元素
s = {23,223,233,2,4,5,6,3,4,1,5,3}
print(s)

# 普通集合内涵
ss = {i for i in s}
print(ss)``````
``````{1, 2, 3, 4, 5, 6, 233, 23, 223}
{1, 2, 3, 4, 5, 6, 233, 23, 223}

``````
``````# 带条件的集合内涵
sss = {i for i in s if i % 2 == 0}
print(sss)``````
``````{2, 4, 6}

``````
``````# 多循环的集合内涵
s1 = {1,2,3,4}
s2 = {"i", "love", "you"}

s = {m*n for m in s2 for n in s1}
print(s)

s = {m*n for m in s2 for n in s1 if n == 2}
print(s)``````
``````{'you', 'youyou', 'love', 'lovelovelovelove', 'lovelovelove', 'lovelove', 'iii', 'youyouyouyou', 'ii', 'i', 'iiii', 'youyouyou'}
{'lovelove', 'youyou', 'ii'}

``````

# 集合函数/关于集合的函数

``````# len，max，min：跟其他基本的函数一致
s = {23,54,72,3,5,3,3,6,1,543}
print(len(s))
print(max(s))
print(min(s))``````
``````8
543
1

``````
``````# set：生成一个集合
l = {1,2,3,4,5,4,3,2,1}
s = set(l)
print(s)``````
``````{1, 2, 3, 4, 5}

``````
``````# add：向集合内添加元素
s = {1}
print(s)``````
``````{1, 3}

``````
``````# clear
s = {1,2,3,4,5}
print(id(s))
s.clear()
print(id(s))
# 结果表明clear函数是原地清空数据``````
``````1370773843528
1370773843528

``````
``````# copy：拷贝
# remove：移除指定的值，直接改变原有值，如果要删除的值不存在，报错
s = {23,4,3,5,1,2,3}
s.remove(4)
print(s)
print(s)

print("*" * 20)
print(s)

s.remove(100)
print(s)``````
``````{1, 2, 3, 5, 23}
{2, 3, 5, 23}
********************
{2, 3, 5, 23}

---------------------------------------------------------------------------

KeyError                                  Traceback (most recent call last)

12 print(s)
13
---> 14 s.remove(100)
15 print(s)

KeyError: 100

``````
``````# pop 随机移除一个元素
s = {1,2,3,4,5,6,7}
d = s.pop()
print(d)
print(s)``````
``````1
{2, 3, 4, 5, 6, 7}

``````
``````# 集合函数
# intersection：交集
# difference：差集
# union：并集
# issubset：检查一个集合是否为另一个子集
# issuperset：检查一个集合是否为另一个超集
s1 = {1,2,3,4,5,6}
s2 = {5,6,7,8,9}

s_1 = s1.intersection(s2)
print(s_1)

s_2 = s1.difference(s2)
print(s_2)

s_3 = s1.issubset(s2)
print(s_3)

s_4 = s1.issuperset(s2)
print(s_4)``````
``````{5, 6}
{1, 2, 3, 4}
False
False

``````
``````# 集合数学操作
s1 = {1,2,3,4,5,6}
s2 = {5,6,7,8,9}

# 以下不支持
s_1 = s1 - s2
print(s_1)

s_2 = s1 + s2
print(s_2)``````
``````{1, 2, 3, 4}

---------------------------------------------------------------------------

TypeError                                 Traceback (most recent call last)

<ipython-input-45-fac787d752ea> in <module>
7 print(s_1)
8
----> 9 s_2 = s1 + s2
10 print(s_2)

TypeError: unsupported operand type(s) for +: 'set' and 'set'

``````

# frozen set ：冰冻集合

• 冰冻就是不可以进行任何修改的操作
• frozenset是一种特殊集合
``````# 创建
s = frozenset()
print(type(s))
print(s)``````
``````<class 'frozenset'>
frozenset()

``````

# dict字典

• 字典是一种组合数据，没有顺序的组合数据，数据以键值对形式出现
``````# 字典的创建
# 创建空字典1
d = {}
print(type(d))
print(d)

# 创建空字典2
d = dict()
print(d)

# 创建有值的字典，每一组数据用冒号隔开，每一对键值对用逗号隔开
d = {"one":1, "two":2, "three":3}
print(d)

# 用dict创建有内容字典1
d = dict({"one":1, "two":2, "three":3})
print(d)

# 用dict创建有内字典2
# 利用关键参数
d = dict(one=1, two=2, three=3)
print(d)

#
d = dict( [("one",1), ("two",2), ("three",3)])
print(d)``````
``````<class 'dict'>
{}
{}
{'one': 1, 'two': 2, 'three': 3}
{'one': 1, 'two': 2, 'three': 3}
{'one': 1, 'two': 2, 'three': 3}
{'one': 1, 'two': 2, 'three': 3}

``````

# 字典的特性

• 字典是序列类型，但是是无序序列，所以没有分片和索引
• 字典中的数据每个都有键值对组成，即kv对

• key：必须是可哈希的值，比如：int，string，float，tuple，但是，list，set，dict不行
• value：任何值

# 字典常见操作

``````# 访问数据
d = {"one":1, "two":2, "three":3}
# 注意访问格式
# 中括号内是键值
print(d["one"])

d["one"] = "eins"
print(d)

# 删除某个操作
# 使用del操作
del d["one"]
print(d)``````
``````1
{'one': 'eins', 'two': 2, 'three': 3}
{'two': 2, 'three': 3}

``````
``````# 成员检测：in，not in
# 成员检测检测时的key内容
d = {"one":1, "two":2, "three":3}

if 2 in d:
print("value")

if "two" in d:
print("key")

if ("two,2") in d:
print("kv")``````
``````key

``````
``````# 遍历在python2 和 3 中区别比较大，代码不通用
# 按key值使用for循环
d = {"one":1, "two":2, "three":3}
# 使用for循环，直接按keu值访问
for k in d:
print(k, d[k])

# 上述代码可以改写如下
for k in d.keys():
print(k, d[k])

# 只访问字典的值
for v in d.values():
print(v)

# 注意以下特殊用法
for k,v in d.items():
print(k, "--", v)``````
``````one 1
two 2
three 3
one 1
two 2
three 3
1
2
3
one -- 1
two -- 2
three -- 3

``````

# 字典生成式

``````d = {"one":1, "two":2, "three":3}

# 常规字典生成式
dd = {k:v for k,v in d.items()}
print(dd)

# 加限制条件的字典生成式
dd = {k:v for k,v in d.items() if v % 2 == 0}
print(dd)``````
``````{'one': 1, 'two': 2, 'three': 3}
{'two': 2}

``````

# 字典相关函数

``````# 通用函数：len，max，min，dict
# str(字典)：用于返回字典的字符串格式
d = {"one":1, "two":2, "three":3}
print(str(d))``````
``````{'one': 1, 'two': 2, 'three': 3}

``````
``````# clear：清空字典
# items：返回字典的键值对组成的元组格式

d = {"one":1, "two":2, "three":3}
i = d.items()
print(type(i))
print(i)``````
``````<class 'dict_items'>
dict_items([('one', 1), ('two', 2), ('three', 3)])

``````
``````# keys：返回字典的键组成的一个结构
k = d.keys()
print(type(k))
print(k)``````
``````<class 'dict_keys'>
dict_keys(['one', 'two', 'three'])

``````
``````# values：同理，一个可迭代的结构
v = d.values()
print(type(v))
print(v)``````
``````<class 'dict_values'>
dict_values([1, 2, 3])

``````
``````# get：根据指定键返回相应的值，好处是，可以生成默认值

d = {"one":1, "two":2, "three":3}
print(d.get("oner"))

# get默认值是None，可以设置
print(d.get("one", 100))
print(d.get("one33", 100))

print(d['on333'])``````
``````None
1
100

---------------------------------------------------------------------------

KeyError                                  Traceback (most recent call last)

<ipython-input-86-f8c01a58018e> in <module>
8 print(d.get("one33", 100))
9
---> 10 print(d['on333'])

KeyError: 'on333'

``````
``````# fromkeys：使用指定的序列作为键，使用一个值作为字典的所有键的值
l = ["eins", "zwei", "dree"]
# 注意fromkeys两个参数的类型
# 注意fromkeys的调用主体
d = dict.fromkeys(l, "hahahahaha")
print(d)``````
``````{'eins': 'hahahahaha', 'zwei': 'hahahahaha', 'dree': 'hahahahaha'}

``````

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