python第三天：数据类型转换

#昨日回顾：

格式化输出 % s d r

第一种1、'%s,%s' % (内容1，内容2)

第二种、dic = {'name':'老男孩'，'age':45}

'%(name)s,%(age)s' % dic

表示单纯的% 用%%

 

while else 语句

如果while循环被break打断，则不走else程序

asicc unicode utf-8 gbk

 

逻辑运算符： not and or

1, () > not > and > or,同一优先级，从左至右执行

2、前后都是数字，x or y,if x True,return x

 

3、基础数据类型

int：计算

 

str：'alix','1233430',存储少量数据。

 

bool： False , True

 

list：['name',True,[]...],各种数据类型的数据，大量的数据。

32位的python的限制是5368710912个元素，64位的python的限制：1152921504606846975个元素，

且列表是是有顺序的。

 

tuple：元组，表现形式：（）只读列表。

 

dict：{} {'name':'老男孩'，

'name_list':['李华',...]

'alex':{'age':40,

'hobby':'old_woman',}

},

存储大量数据，关系型数据。一个栈对应一个值的存储方式

 

set:集合

set{'wu sir','alex',...}

 

 

 

#int

# i = 7

# print(i.bit_length())

#十进制转换成二进制的最小有效位数

 

'''

1 0000 0001

2 0000 0010

3 0000 0011

100

'''

 

 

'''

int <--> str

str --> int int(str) 条件：字符串必须全部由数字组成

int ---> str str(int)

bool ---> int True --> 1 False --> 0

int ---> bool 非零即为True,零即为False

bool --> str str(True) str(False)

str --> bool 非空即为True ''空字符串--->False

'''

 

 

# age = int(input('>>>'))

# print(age,type(age))

 

s1 = str(123)

s2 = 123

print(s1, s2, type(s1), type(s2))

 

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

123 123 <class 'str'> <class 'int'>

 

Process finished with exit code 0

 

 

举例：

print(int(True))

print(int(False))

 

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

1

0

 

Process finished with exit code 0

 

举例：

print(bool(100))

print(bool(0))

print(bool(-23))

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

True

False

True

 

Process finished with exit code 0

 

bool --> str str(True) str(False)

print(str(True))

print(str(False))

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

True

False

 

Process finished with exit code 0

 

 

str --> bool 非空即为True

print(bool('adnf'))

print(bool(''))

print(bool('0'))

print(bool(0))

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

True

False

True

False

 

Process finished with exit code 0

 

测试验证上面关系

s1 = ' ' #''之间有空格

if s1:

print(666)

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

666

 

Process finished with exit code 0

 

再换个形式测试：

s1 = '' #’‘之间没空格

if s1:

print(666)

 

测结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

 

Process finished with exit code 0

 

 

str部分：索引功能

#str 索引 切片和歩长

s = 'Python12期' #字符串的索引从左至右是0开始

s1 = s[0]

print(s1)

 

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

P

 

Process finished with exit code 0

 

索引拿出的字段还是字符串：

#str 索引 切片和歩长

s = 'Python12期sdfasdf' #字符串的索引从左至右是0开始

s1 = s[0]

s2 = s[4]

s3 = s[8]

s4 = s[-1]

 

print(s1,type((s1)))

print(s2)

print(s3)

print(s4)

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

P <class 'str'>

o

期

f

 

Process finished with exit code 0

 

 

str的切片功能

s = 'Python12期sdfasdf' #切片顾头不顾尾

s6 = s[0:6]

s7 = s[:6]

s8 = s[2:5]

s9 = s[1:] #切片取最后一位，需省略写：后数字

s10 = s[:] #切片如果取全部，直接在：前后的数字去掉

print(s6)

print(s7)

print(s8)

print(s9)

print(s10)

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

Python

Python

tho

ython12期sdfasdf

Python12期sdfasdf

 

Process finished with exit code 0

 

 

#str的歩长功能

s = 'Python12期' #取P、t、o,格式[首位：末尾：长度]

s11 = s[:5:2]

s12 = s[4::2] #取o、1、期,格式[首位：末尾：长度]

print(s11)

print(s12)

 

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

Pto

o1期

 

Process finished with exit code 0

 

 

反向切片和歩长：

s = 'Python12期' #反向取值：期到n，格式[反向起始位：反向结束位（+1）：歩长值]

s13 = s[-1:-5:-1]

print(s13)

 

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

期21n

 

Process finished with exit code 0

 

 

s = 'Python12期' #反向取值：期和1，格式[反向起始位：反向结束位：-2]

s13 = s[-1:-5:-2]

print(s13)

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

期1

 

Process finished with exit code 0

 

 

#字符串的常用方法：

#首字母大写：capitalize

s = 'laoNANhai'

s1 = s.capitalize()

print(s1)

#

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

Laonanhai

 

Process finished with exit code 0

 

# * center 格式：center（长度值）

#center

s = 'laoNANhai'

s2 = s.center(20)

s3 = s.center(20, "*")

print(s2)

print(s3)

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

laoNANhai

*****laoNANhai******

 

Process finished with exit code 0

 

 

# *** upper 全部大写 lower 全部小写

s = 'laoNANhai'

s12 = s.upper()

s13 = s.lower()

 

print(s12)

print(s13)

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

LAONANHAI

laonanhai

 

Process finished with exit code 0

 

 

#实际案例：不区分大小写验证码

code = 'AQdr'.upper()

your_code = input('请输入验证码，不区分大小写：').upper()

if your_code == code:

print('验证成功！')

else:

print('输入错误，请重新输入！')

 

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

请输入验证码，不区分大小写：aqdr

验证成功！

 

Process finished with exit code 0

 

 

#startwith和endswith

s = 'laoNANhai'

# *** startwith：以**为开头 endswith：以**为结尾

#返回bool,可以切片，切片用逗号隔开。

s20 = s.startswith('l')

s21 = s.endswith('i')

s22 = s.endswith('a')

s23 = s.startswith('lao')

s24 = s.endswith('hai')

s25 = s.startswith('N', 3, 6)

s26 = s.endswith('h', 0, -2)

print(s20)

print(s21)

print(s22)

print(s23)

print(s24)

print(s25)

print(s26)

 

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

True

True

False

True

True

True

True

 

Process finished with exit code 0

 

#swap:大小写翻转

s = 'laoNANhai'

s30 = s.swapcase()

print(s30)

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

LAOnanHAI

 

Process finished with exit code 0

 

 

# * title 被非字母隔开的每个单词的首字母大写

ss = 'gdex wusri43basde*sdfritian'

s40 = ss.title()

print(s40)

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

Gdex Wusri43Basde*Sdfritian

 

Process finished with exit code 0

 

 

#***通过元素找索引：find、index

#index:通过元素找索引,可切片，找不到会报错

#find:通过元素找索引，可切片，找不到返回-1

s = 'laoNANhai'

s50 = s.find('l')

s51 = s.find('a')

s52 = s.find('a', 2, ) #找第二个a

s53 = s.find('A', 2, ) #找A

print(s50)

print(s51)

print(s52)

print(s53)

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

0

1

7

4

 

Process finished with exit code 0

 

 

index与find的区别：

find

s = 'sdf ;lskd12*lsd-sd'

s7 = s.find('B')

print(s7)

测试结果：

D:\pythonProject\venv\Scripts\python.exe D:/pythonProject/homework.py

-1

 

Process finished with exit code 0

 

index：

s = 'sdf ;lskd12*lsd-sd'

s8 = s.index('B')

print(s8)

测试结果：

File "D:\pythonProject\homework.py", line 124, in <module>

s8 = s.index('B')

ValueError: substring not found

 

Process finished with exit code 1

 

#*** strip：去除前后空格键、换行符，制表符

ss1 = '\talex ' # \t 表示4个空格，或者一个tab键

ss2 = ' alex\n ' # \n 表示换行符

print(ss1)

print(ss2)

测试结果：

D:\pythonProject\venv\Scripts\python.exe D:/pythonProject/homework.py

alex

alex

 

 

Process finished with exit code 0

 

strip实际案例：

username = input('请输入用户名：')

if username == '洪嘟嘟':

print('登录成功！')

else:

print('输入错误，请重新输入！')

测试结果1：

D:\pythonProject\venv\Scripts\python.exe D:/pythonProject/homework.py

请输入用户名：洪嘟嘟 #洪嘟嘟后无空格

登录成功！

 

Process finished with exit code 0

 

测试结果2：

D:\pythonProject\venv\Scripts\python.exe D:/pythonProject/homework.py

请输入用户名：洪嘟嘟 #洪嘟嘟后面加了空格

输入错误，请重新输入！

 

Process finished with exit code 0

 

如何解决输入时前后有空格的情况？通过加strip实现自动去除：

# strip实际案例：

username = input('请输入用户名：').strip()

if username == '洪嘟嘟':

print('登录成功！')

else:

print('输入错误，请重新输入！')

测试结果：

D:\pythonProject\venv\Scripts\python.exe D:/pythonProject/homework.py

请输入用户名： 洪嘟嘟 # 洪嘟嘟 前后都加了空格也没关系

登录成功！

 

Process finished with exit code 0

 

 

# 案例2：strip去除前后的关键字

ss = 'alexssdsd'

s9 = ss.strip('a')

print(s9)

测试结果：

D:\pythonProject\venv\Scripts\python.exe D:/pythonProject/homework.py

lexssdsd

 

Process finished with exit code 0

 

# 案例3：strip去除前后的关键字

ss = 'alexssdsd'

s9 = ss.strip('l')

print(s9)

测试结果：

D:\pythonProject\venv\Scripts\python.exe D:/pythonProject/homework.py

alexssdsd #此种情况不是字符前后的，所以无法去除！

 

Process finished with exit code 0

 

# 案例4：strip去除前后的关键字

ss = 'dalexssdsd'

s9 = ss.strip('d')

print(s9)

测试结果：

D:\pythonProject\venv\Scripts\python.exe D:/pythonProject/homework.py

alexssds

 

Process finished with exit code 0

 

# 案例5：strip去除单词关键字前后的字

ss = 'dalexssdsd'

s9 = ss.strip('d')

s10 = ss.strip('da') #将d和a分别做关键字去除前后的关键字

 

print(s9)

print(s10)

测试结果：

D:\pythonProject\venv\Scripts\python.exe D:/pythonProject/homework.py

alexssds

lexssds

 

Process finished with exit code 0

 

# 案例6：lstrip去左边或rstrip去除右边的关键字

ss = 'dalexssdsd'

s9 = ss.lstrip('d')

s10 = ss.rstrip('d')

 

print(s9)

print(s10)

测试结果：

D:\pythonProject\venv\Scripts\python.exe D:/pythonProject/homework.py

alexssdsd

dalexssds

 

Process finished with exit code 0

 

#*** split:将字符串分割成列表,

# 默认是用空格隔开，相当于 str ---> list

s = 'wusir alex taibei'

st = 'wusir,alex,taibei'

st1 = 'QwusirQalexQtaibei'

s1 = s.split()

s2 = st.split(',')

s3 = st1.split('Q')

s4 = st1.split('Q',2) #最后的数字，表示分割几次

 

print(s1)

print(s2)

print(s3)

print(s4)

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

['wusir', 'alex', 'taibei']

['wusir', 'alex', 'taibei']

['', 'wusir', 'alex', 'taibei']

['', 'wusir', 'alexQtaibei']

 

Process finished with exit code 0

 

 

# ***join参数

# 在某些情况下，list --->str

s = 'alex'

s11 = '+'.join(s)

print(s11)

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

a+l+e+x

 

Process finished with exit code 0

 

join功能实现2：

l = ['wusir', 'alex', 'taibai']

st11 = ''.join(l) #''之间没空格

st12 = ' '.join(l) #''之间有空格

print(st11,type(st11))

print(st12,type(st12))

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

wusiralextaibai <class 'str'>

wusir alex taibai <class 'str'>

 

Process finished with exit code 0

 

 

说明：join前提是list中必须都是str

l1 = [1, 'alex', 'taibai'] #l1中第一个改成了数字后测试

st13 = ' '.join(l1)

print(st13,type(st13))

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

Traceback (most recent call last):

File "D:/pycharm/project/day03/数据类型转换.py", line 215, in <module>

st13 = ' '.join(l1)

TypeError: sequence item 0: expected str instance, int found

 

Process finished with exit code 1

 

 

 

# ****replace：替换功能

# replace

s = '小粉嫩小粉嫩sdsdfax小粉嫩'

s12 = s.replace('小粉嫩', '长沙')

s13 = s.replace('小粉嫩', '长沙', 2) #最后的数字表示替换次数

print(s12)

print(s13)

测试结果：

C:\Users\hongd\AppData\Local\Programs\Python\Python38\python.exe D:/pycharm/project/day03/数据类型转换.py

长沙长沙sdsdfax长沙

长沙长沙sdsdfax小粉嫩

 

Process finished with exit code 0

 

 

 

# 公共方法：

# len()

s = 'sdfasdfsaadfs'

# 公共方法：

# len() 总个数

print(len(s))

# count 计算某元素出现次数，可切片

c1 = s.count('a')

c2 = s.count('a', 4, -1)

print(c1)

print(c2)

测试结果：

D:\pythonProject\venv\Scripts\python.exe D:/pythonProject/homework.py

13

3

2

 

Process finished with exit code 0

 

 

# format 格式化输出三种方式

# 1，

msg = '我叫{}，今年{}，爱好{}'.format('太白', '20', 'girl')

print(msg)

 

#2，

msg1 = '我叫{0}，今年{1}，爱好{2}，我依然叫{0}'.format('太白', '20', 'girl')

print(msg1)

 

#3，

msg2 = '我叫{name}，今年{ago}，爱好{hobby}'.format(name='太白', hobby='girl',ago='20')

print(msg2)

 

#3-2 #\表示不回车的换行，对于一行比较长的内容，可以通过次方式来换行。

msg3 = '我叫{name}，今年{ago}，爱好{hobby}'.\

format(name='太白', hobby='girl',ago='20')

print(msg3)

测试结果：

D:\pythonProject\venv\Scripts\python.exe D:/pythonProject/homework.py

我叫太白，今年20，爱好girl

我叫太白，今年20，爱好girl，我依然叫太白

我叫太白，今年20，爱好girl

我叫太白，今年20，爱好girl

 

Process finished with exit code 0

 

 

# isalnum\ isalpha\ isdigit

name = 'jisan233'

print(name.isalnum()) #字符串有字母或数字组成

print(name.isalpha()) #字符串只由字母组成

print(name.isdigit()) #字符串只由数字组成

测试结果：

D:\pythonProject\venv\Scripts\python.exe D:/pythonProject/homework.py

True

False

False

 

Process finished with exit code 0

 

 

#作业：s = 'sdfasdjowskdm' 使用while分别打印每个字符内容

s = 'asdfghjkl;'

办法1：

count = 0

while count < len(s):

print(s[count])

count += 1

测试结果：

D:\pythonProject\venv\Scripts\python.exe D:/pythonProject/homework.py

a

s

d

f

g

h

j

k

l

;

 

Process finished with exit code 0

 

#办法2： for:有限循环，而while是无限循环

# for:有限循环，而while是无限循环

# 格式：for 变量 in 可迭代对象

pass

#举例1：

s = 'asdfghjkl;'

for i in s:

print(i)

测试结果：

D:\pythonProject\venv\Scripts\python.exe D:/pythonProject/homework.py

a

s

d

f

g

h

j

k

l

;

 

Process finished with exit code 0

 

举例2：

for i in s:

print(i + 'ing')

测试结果：

D:\pythonProject\venv\Scripts\python.exe D:/pythonProject/homework.py

aing

sing

ding

fing

ging

hing

jing

king

ling

;ing

 

Process finished with exit code 0