一、python的数据类型
1.python的基本数据类型包括数值数据类型和字符串数据类型；基本数据类型的特点是不允许改变，如果改变基本数据类型的值，会导致内存的重新分配。
image
2.数值的相互转换函数
image
3.变量的三个属性
image
4.判断某个变量是否是某种类型实例
print(isinstance(3, float)) #False
5.复数类型的使用
a = complex(2,2)
b = complex("3+2j")
print(a)
print(b)
print(a+b)
print(a-b)
print(a*b)
print(a/b)
(2+2j)
(3+2j)
(5+4j)
(-1+0j)
(2+10j)
(0.7692307692307692+0.15384615384615388j)
6.python的字符串类型不像Java可以与数值类型相加，如“str”+1会报错，但python支持字符串与数值相乘，表示将字符串重复多少次。
#报错
#print("str"+1)<br>
#重复字符串
print("The life is short,i love python\n" * 3) #The life is short,i love python
#The life is short,i love python
#The life is short,i love python<br>
#转为大写
print("lower".upper()) #LOWER<br>
#转为小写
print("UPPER".lower()) #upper
<br><br>#去除前导和尾部空白
print(" hello python ".strip()) #hello python
<br><br>#也可以指定去除的字符
print("##hello python##!".strip("#!")) #hello python
<br><br>#求长度
print(len("hello")) #5
<br><br>#拆分字符串
print("orange banana apple".split(" ")) #['orange', 'banana', 'apple']
<br><br>#用指定字符串连接一个列表
print(" ".join(["orange","apple","banana","peach"])) #orange apple banana peach
<br><br>#判断字符串是否以某个子串开始
print("good good study".startswith("go")) #True
<br><br>#判断字符串是否以某个子串开始
print("day day up".endswith("up")) #True
<br><br>#统计子串出现次数
print("Python is a nascent programming language.".count("p")) #1
<br><br>#查找子串出现的下标
print("Sometimes your whole life boils down to one insane move.".find("wh")) #15
<br><br>#判断是否是数字
print("moive".isdigit()) #False
<br><br>#判断是否是字母
print("money".isalpha()) #True
<br><br>#判断是否是空格
print("i declared".isspace()) #False
7.Python的字符串最强大之处是切片操作
str = "Attitude determines altitude."
#取出Attitude（外国人的习惯是左闭右开，即包括左下标，不包括右下标）
print(str[0:9]) #Attitude
print(str[0:20:3]) #Aiddeis (每3个取一个)
print(str[-5:-1]) #tude
8.Python的字符串可以用单引号，双引号，三引号表示，但字符串跨行时只能用三引号或反斜杠
str = '''Be
a
laborious
bee
'''
print(str)
str1 = "Be \
a \
hard-working \
man"
print(str1) #Be a hard-working man
9.实现字符串反转
#切片 str[开始位置：结束位置：步数] 将步数设为-1
def strReverse1(str):
return str[::-1]
#将字符串转为列表，反转后再连接为字符串
def strReverse2(str):
newList = list(str)
newList.reverse()
return "".join(newList)
print(strReverse1("python"))
print(strReverse2("python"))
二、输入输出
1、输入函数input()
#输入一个字符串
myStr = input("请输入一个字符串：")
print(myStr)
#以逗号分割输入多个数
a,b,c = eval(input("请输入3个数:"))
print(a,b,c)
2.输出函数 print()
#以逗号分割输出多个变量，输出后显示的分隔符是空格,结尾会输出一个换行符
print("i","am","studying","python") #i am studying python
#指定分隔符和结尾符
print("i","am","studying","python",sep="#",end=" ")
print()
#类似c语言的输出
name = "jackson"
age = 22
salary = 5000.0
print("name:%s,age:%d,salary:%.3f" % (name,age,salary))
#python特有的输出形式
print("I like eating {} and {}".format("banana", "pear"))
print("His name is {name} and he is a {sex}".format(sex='male',name='judy'))
print("{1} can arm our {0}".format("brain","knowledge"))
print("The happiness rate of chinese citizen is up to {:.3f}".format(0.45))
print("The population of china is {:,d} million".format(1300))
三、集合数据类型
Python学习交流群：556370268，有资源共享，经验分享，这里是python学习者聚集地，欢迎喜欢Python的小伙伴！
Python的集合数据类型包括列表，元组，字典，集合
image
1.列表
#四种遍历方式
for item in fruits:
print(item,end=" ")
print()
for item in iter(fruits):
print(item,end=" ")
print()
for i,item in enumerate(fruits):
print(i,"===>",item,end=" ")
print()
for item in range(len(fruits)):
print(fruits[item],end=" ")
print()
#重复列表四次
print(fruits*4) #['orange', 'banana', 'pear', 'peach', 'orange', 'banana', 'pear', 'peach', 'orange', 'banana', 'pear', 'peach', 'orange', 'banana', 'pear', 'peach']
#列表连接
print(fruits+["pineapple","apple"])
#删除指定下标的元素，不提供参数则删除表尾元素
print(fruits.pop(2)) #['orange', 'banana', 'pear', 'peach', 'pineapple', 'apple']
#追加元素 append追加和extend追加有区别
#append追加的是列表
#extend追加的是元素
fruits.append(["Coconut"])
print(fruits) #['orange', 'banana', 'peach', ['Coconut']]
fruits.pop()
fruits.extend(["Coconut"])
print(fruits) #['orange', 'banana', 'peach', 'Coconut']
#列表反转
fruits.reverse()
print(fruits) #['Coconut', 'peach', 'banana', 'orange']
#指定位置插入
fruits.insert(2, "nothing")
print(fruits) #['Coconut', 'peach', 'nothing', 'banana', 'orange']
#删除列表切片
del fruits[1:3]
print(fruits) #['Coconut', 'banana', 'orange']
2.元组
myTuple1 = ("bird","plane","vehicle","subway")
#不能对单个元素重新赋值(报错)
#myTuple1[0] = "parrot"
#但可以对整个元组赋值
myTuple1 = ("python","c++","java")
print(myTuple1) #('python', 'c++', 'java')
#创建空元组
emptyTuple = ()
print(emptyTuple) #()
#注意创建一个元素的元组要在结尾加逗号
oneTuple = (1)
print(oneTuple) #1 不加逗号编译器会认为括号是进行算数运算，而不是创建元组
oneTuple = (1,)
print(oneTuple) #(1,)
#元组的取值
print(myTuple1[0]) #python
print(myTuple1[:]) #('python', 'c++', 'java')
print(myTuple1[:1]) #('python',)
print(myTuple1[len(myTuple1)-1:]) #('java',)
#元组的重复
print(myTuple1 *4) #('python', 'c++', 'java', 'python', 'c++', 'java', 'python', 'c++', 'java', 'python', 'c++', 'java')
#元组相加
print(myTuple1 + ("one","two","three")) #('python', 'c++', 'java', 'one', 'two', 'three')
3.字典
myDict = {"one":1,"two":343.33,"three":True}
#字典的取值
print(myDict["one"]) #1
#判断键是否存在
print("three" in myDict) #True
#更新值
myDict["one"] = 100
print(myDict) #{'one': 100, 'two': 343.33, 'three': True}
#清空字典
myDict.clear()
print(myDict) #{}
4.集合
#以字符串创建set
mySet = set("hello")
print(mySet) #{'o', 'l', 'e', 'h'}
#以list创建set,自动去除重复元素
mySet1 = set(["a","m","e","o"])
print(mySet1) #{'o', 'a', 'm', 'e'}
#以map创建set，值为map的键
mySet2 = set({"name":1,"age":2})
print(mySet2) #{'name', 'age'}
#交集
print(mySet & mySet1) #{'e', 'o'}
#并集
print(mySet | mySet1) #{'l', 'a', 'e', 'h', 'm', 'o'}
#差集
print(mySet - mySet1) #{'l', 'h'}
#对称差分运算
print(mySet ^ mySet1) #{'l', 'a', 'h', 'm'}
四、强大的列表解析功能
import random
#列表解析
#生成10个随机数
list1 = [random.randint(0,100) for i in range(0,10)]
for item in list1:
print(item,end=" ") #74 38 75 45 96 1 38 93 58 80
print()
list2 = [i*i for i in range(1,21)]
for num in list2:
print(num,end=" ") #1 4 9 16 25 36 49 64 81 100 121 144 169 196 225 256 289 324 361 400
#选出list2中的偶数
list3 = [i for i in list2 if i % 2 == 0]
for num in list3:
print(num) #4 16 36 64 100 144 196 256 324 400
#按行遍历矩阵
list4 = [[1,2,3,4],[5,6,7,8],[2,3,4,5],[6,7,8,9]]
list5 = [[1,4,5,6],[2,1,3,4],[3,4,2,1],[7,8,2,1]]
print([row for row in list4]) #[[1, 2, 3, 4], [5, 6, 7, 8], [2, 3, 4, 5], [6, 7, 8, 9]]
#按列遍历矩阵
print([list4[row][1] for row in range(len(list4))]) #[2, 6, 3, 7]
#遍历对角线
print([list4[i][i] for i in range(len(list4))]) # [1, 6, 4, 9]
#逐个遍历
print([list4[row][col] for row in range(len(list4)) for col in range(len(list4[row]))]) #[1, 2, 3, 4, 5, 6, 7, 8, 2, 3, 4, 5, 6, 7, 8, 9]
#矩阵相加
print([list4[row][col] + list5[row][col] for row in range(list4.__len__()) for col in range(list4[row].__len__())])
#[2, 6, 8, 10, 7, 7, 10, 12, 5, 7, 6, 6, 13, 15, 10, 10]
#转置矩阵
print([row for row in zip(*list4)]) #[(1, 5, 2, 6), (2, 6, 3, 7), (3, 7, 4, 8), (4, 8, 5, 9)]
#求最大长度对应的字符
students = ["jack","shirely","kangkang","mary"]
maxLen = max([len(item) for item in students])
print(maxLen)
maxStr = [temp for temp in students if len(temp) == maxLen]
print(maxStr) #['kangkang']
五、内置函数
#几个内置的高阶函数 map,filter,reduce,sorted
#map用于将一函数规则应用于一可迭代集合的所有元素
#reduce用于将一函数规则反复作用于一可迭代集合的元素，传入的函数参数必须为两个
#filter将一可迭代集合中适用于函数规则的元素挑选出来
#sorted用于对可迭代集合进行排序
#map的一个栗子(将字符串转为对应数字)
f = lambda ch:{"0":0,"1":1,"2":2,"3":3,"4":4,"5":5,"6":6,"7":7,"8":8,"9":9}[ch]
f1 = lambda ch:int(ch)
print(list(map(f,"322"))) #[3, 2, 2]
#reduce的一个栗子(将字符串转换为对应的十进制数)
def str2Decimal(x,y):
return x*10 + y
print(reduce(str2Decimal,map(f,"232"))) #232
#filter的一个栗子(使用埃氏筛选法筛选素数)
seq = range(2,51)
for i in seq:
f = lambda x : x == i or x % i
seq = list(filter(f,seq))
print(list(seq)) #[2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47]
#sorted的一个栗子
rules = lambda x:x.lower()
reles2 = lambda x:x["age"]
students = ["jack","Nacy","Kangkang","asia"]
aMap = [{"name":"kangknag","age":25},{"name":"ag","age":13},{"name":"wnag","age":23}]
newlist = sorted(students, key=rules, reverse=False)
print(sorted(aMap,key=reles2)) #[{'name': 'ag', 'age': 13}, {'name': 'wnag', 'age': 23}, {'name': 'kangknag', 'age': 25}]
print(newlist) #['asia', 'jack', 'Kangkang', 'Nacy']
网友评论