Python basic Three

Conversion between data types Int<-->str

int转str:str(digit)str转int:int(string) 注意此处的string只能是包含数字的字符串或开头有负号

Int<-->bool

bool(非零)-->Truebool(零)  -->Falseint(True) -->1int(False)-->0

Bool<-->str

bool -->str没有实际意义str  -->bool:bool(非空字符串) --> Truebool(空字符串)   --> False注意：空字符串为''，而不是' '。

The learning of the Python string (string) The first part: The index tile step is indexed by the index, and the resulting string is a character.

>>> str1 = 'python'>>> str1[2]'t'>>> str1[-1]'n'

By slicing the value, Gu Tou regardless of the tail

>>> str2 = 'python'>>> str2[0 : -1]'pytho'>>> str2[0:]'python'

by Slice + step

>>> str3 = 'python is a language'>>> str3[::2]'pto salnug'>>> str3[::-1]'egaugnal a si nohtyp'当步长为负时，是倒着取值。

Alternatively, you can use an array to reverse the string

strA = input("请输入需要翻转的字符串：")order = [] for i in strA:  order.append(i)order.reverse()   #将列表反转print ''.join(order)    #将list转换成字符串

The second part: the common method of string. Capitalize () First letter capital ★★☆☆☆

>>> str4 = 'hellokitty'>>> str4.capitalize()'Hellokitty'

Center () strings are populated before and after the custom character ★★☆☆☆

>>> str4 = 'hellokitty'>>> str4.center(20, '*')'*****hellokitty*****'

Upper () English full capitalization; lower () English all lowercase. It will be used on verification code verification. ★★★★★

>>> str4 = 'hello kitty'>>> str4.upper()'HELLO KITTY'>>> str5 = 'Hello Kitty'>>> str5.lower()'hello kitty'

Swapcase () Case Flip ★★☆☆☆

>>> str5 = 'Hello Kitty'>>> str5.swapcase()'hELLO kITTY'

Title () The first letter of each part that is not separated by the letter is capitalized ★★☆☆☆

>>> str6 = 'hello kitty,what can I do4you?'>>> str6.title()'Hello Kitty,What Can I Do4You?'

StartsWith () with what EndsWith () with what end ★★★★★

>>> str6 = 'hello kitty,what can I do4you?'>>> str6.startswith('h')True>>> str6.startswith('hello')True

Find finds the index by element, returns the first one, and returns without this element -1★★★★★

>>> str6 = 'hello kitty,what can I do4you?'>>> str6.find('h')0>>> str6.find('what')12>>> str6.find('.')-1

Index is indexed by element, and the first one is returned without this element error ★★★★★

>>> str6 = 'hello kitty,what can I do4you?'>>> str6.index('h')0>>> str6.index('what')12>>> str6.index('.')Traceback (most recent call last):  File "<stdin>", line 1, in <module>ValueError: substring not found

Strip default to remove spaces before and after a string, line breaks, tab ★★★★★

>>> str7 = "\tI'm a superman. ">>> str7.strip()"I'm a superman.">>> str7 = '==hey guys, you shutup!=='>>> str7.strip('==')'hey guys, you shutup!'

Lstrip () Rstrip ()

lstrip()是去除左边的。rstrip()是去除右边的。

Split () splits the string into a list (str---> List), which is separated by a space by default and can specify characters. ★★★★★

>>> str8 = 'spring summer autumn winter'>>> str8.split()['spring', 'summer', 'autumn', 'winter']>>> str8 = 'spring,summer,autumn,winter'>>> str8.split(',')['spring', 'summer', 'autumn', 'winter']

split face question★★★★★

一般有n个分割符，就有n+1个列表元素。但有个特例：当字符串开头有一个空格时并不指定分割符，就只会有n个列表元素。>>> str8 = ' spring summer autumn winter'>>> str8.split()['spring', 'summer', 'autumn', 'winter']>>> str8.split(' ')['', 'spring', 'summer', 'autumn', 'winter']

Split ([Sep [, Maxsplit]]) to set the number of splits.

>>> str8.split(',', 1)['spring', 'summer,autumn,winter']可以用在分割路径与文件名：  ★★★★★>>> file_path = r'E:\aaa\bbb\ccc.ddd'>>> path, file = file_path.rsplit('\\', 1)>>> path'E:\\aaa\\bbb'>>> file'ccc.ddd'

Join custom connector to connect elements in an iterative object ★★★★★

>>> s1 = 'abc'>>> '_'.join(s1)'a_b_c'

Replace replacement string, you can specify the number of substitutions ★★★★★

>>> s2 = "Jack is Mary's boy friend.">>> s2.replace('Jack', 'Mark')"Mark is Mary's boy friend.">>> s2.replace('a', 'o', 1)"Jock is Mary's boy friend."

Formatted output: Format

s1 = '我叫{},今年{}，性别{}'三种方式第一种s2 = '我叫{},今年{}，性别{}'.format('太白','28','男')print(s2)第二种s3 = '我叫{0},今年{1}，性别{2}，我依然叫{0}'.format('太白', '28', '男')print(s3)第三种s4 = '我叫{name},今年{age}，性别{sex}'.format(age='28', name='太白', sex='男')print(s4)

Is series

name = 'taibai'name1 = 'a123'print(name.isalnum())  # 数字或字母组成print(name1.isdigit())  # 判断全部是由整数组成print(name.isalpha())  # 全部由字母组成

Public methods

>>> name='alexaaaa'>>> name.count('a')  #可以设置起始位置，结束位置。5>>> print(len(name))8

Python basic Three