continue ,终止当前循环，开始下一次循环
break ,终止所有循环
用户登陆（三次机会重试）
count = 0 while count < 3: user = input('>>>') pwd = input('>>>') if user == 'pangqi' and pwd == '123': print('欢迎登陆') print('..........') break else: print('用户名或者密码错误') count = count + 1
1、运算符
结果是值
算数运算
a = 10 * 10
赋值运算
a = a + 1 a+=1
结果是布尔值
比较运算
a = 1 > 5
逻辑运算
a = 1>6 or 1==1
成员运算
a = "o" in "pangqi"
2、基本数据类型
- int
将字符串转换为数字
a = "123" print(type(a),a) b = int(a) print(type(b),b) num = "0011" v = int(num, base=16) print(v) - bit_length # 当前数字的二进制，至少用n位表示 r = age.bit_length()
字符串 str
# 1 capitalize:首字母大写
# test = "pangqi"
# v = test.capitalize()
# print(v)
# 2 casefold:所有变小写，casefold更牛逼，很多未知的对相应变小写
# v1 = test.casefold()
# print(v1)
# v2 = test.lower()
# print(v2)
# 3 center:设置宽度，并将内容居中
# 20 代指总长度
# * 空白位置填充一个字符，可有可无
v = test.center(20,"中") print(v) test = "pangqi" v = test.ljust(20,"*") print(v) test = "pangqi" v = test.rjust(20,"*") print(v) test = "pangqi" v = test.zfill(20) print(v)
# 4 count:去字符串中寻找，寻找子序列的出现次数
# test = "aLexalexr"
# v = test.count('ex')
# print(v)
# test = "aLexalexr"
# v = test.count('ex',5,6)
# print(v)
# 5 startwith/endswith
# 以xx结尾
# 以xx开始
# test = "alex"
# v = test.endswith('ex')
# v = test.startswith('ex')
# print(v)
# 6 expandtabs,断句20，
# test = "username\temail\tpassword\nlaiying\[email protected]\t123\nlaiying\[email protected]\t123\nlaiying\[email protected]\t123"
# v = test.expandtabs(20)
# print(v)
# 7 find:从开始往后找，找到第一个之后，获取其位置
# test = "pangqishishagua"
# 未找到
# v = test.find('sh')
# print(v)
# 8 index找不到，报错忽略
# test = "pangqiqi"
# v = test.index('8')
# print(v)
# 9 format:格式化，将一个字符串中的占位符替换为指定的值
# test = 'i am {name}, age {a}'
# print(test)
# v = test.format(name='pangqi',a=19)
# print(v)
# test = 'i am {0}, age {1}'
# print(test)
# v = test.format('pangqi',19)
# print(v)
# 10 format:格式化，传入的值 {"name": 'alex', "a": 19}
# test = 'i am {name}, age {a}'
# v1 = test.format(name='df',a=10)
# v2 = test.format_map({"name": 'pangqi', "a": 19})
# 11 isalnum:字符串中是否只包含 字母和数字
# test = "123"
# v = test.isalnum()
# print(v)
# str
# 12 isalpha:是否是字母，汉字
# test = "as2df"
# v = test.isalpha()
# print(v)
# 13 isdecimal:当前输入是否是数字
# test = "二" # 1，②都可以
# v1 = test.isdecimal()
# v2 = test.isdigit()
# v3 = test.isnumeric()
# print(v1,v2,v3)
# 14 isprintable:是否存在不可显示的字符
# \t 制表符
# \n 换行
# test = "oiuas\tdfkj"
# v = test.isprintable()
# print(v)
# 15 isspace:判断是否全部是空格
# test = ""
# v = test.isspace()
# print(v)
# 16 istitle:判断是否是标题
# test = "Return True if all cased characters in S are uppercase and there is"
# v1 = test.istitle()
# print(v1)
# v2 = test.title()
# print(v2)
# v3 = v2.istitle()
# print(v3)
# 17 join:将字符串中的每一个元素按照指定分隔符进行拼接
# test = "宿舍里面有个傻逼"
# print(test)
# # t = ' '
# v = "_".join(test)
# print(v)
# 18 islower/isupper:判断是否全部是大小写 和 转换为大小写
# test = "Alex"
# v1 = test.islower()
# v2 = test.lower()
# print(v1, v2)
# v1 = test.isupper()
# v2 = test.upper()
# print(v1,v2)
# 19 lstrip/rstrip/strip
# 移除指定字符串
# 有限最多匹配
# test = "xa"
# # v = test.lstrip('xa')
# v = test.rstrip('9lexxexa')
# # v = test.strip('xa')
# print(v)
# test.lstrip()
# test.rstrip()
# test.strip()
# 去除左右空白
# v = test.lstrip()
# v = test.rstrip()
# v = test.strip()
# print(v)
# print(test)
# 去除\t \n
# v = test.lstrip()
# v = test.rstrip()
# v = test.strip()
# print(v)
# 20 maketrans:对应关系替换
# test = "aeiou"
# test1 = "12345"
# v = "asidufkasd;fiuadkf;adfkjalsdjf"
# m = str.maketrans("aeiou", "12345")
# new_v = v.translate(m)
# print(new_v)
# 21 partition:分割
# test = "testasdsddfg"
# v = test.partition('s')
# print(v)
# v = test.rpartition('s')
# print(v)
# 22 split:分割为指定个数
# v = test.split('s',2)
# print(v)
# test.rsplit()
# 23 splitlines:分割，只能根据，true，false：是否保留换行
# test = "asdfadfasdf\nasdfasdf\nadfasdf"
# v = test.splitlines(False)
# print(v)
# 24 startswith/endswith:以xxx开头，以xx结尾
# test = "backend 1.1.1.1"
# v = test.startswith('a')
# print(v)
# test.endswith('a)
# 25 swapcase:大小写转换
# test = "aLex"
# v = test.swapcase()
# print(v)
# 26 isidentifier:字母，数字，下划线 ： 标识符 def class
# a = "def"
# v = a.isidentifier()
# print(v)
# 27 replace:将指定字符串替换为指定字符串
# test = "alexalexalex"
# v = test.replace("ex",'bbb')
# print(v)
# v = test.replace("ex",'bbb',2)
# print(v)
总结：
# join # '_'.join("asdfasdf")
# split
# find
# strip
# upper
# lower
# replace
# 一、for循环
# for 变量名 in 字符串:
# 变量名
# break
# continue
# index = 0 # while index < len(test): # v = test[index] # print(v) # index += 1 # print('=======') # for zjw in test: # print(zjw) # test = "1234567" # for item in test: # print(item) # break # for item in test: # continue # print(item)
# 二、索引，下标，获取字符串中的某一个字符
# v = test[3]
# print(v)
# 三、切片
# v = test[0:-1]
# print(v)
# 四、获取长度
# Python3： len获取当前字符串中由几个字符组成
# v = len(test)
# print(v)
# 五、获取连续或不连续的数字
# python3中只有for循环时，才一个一个创建
# r1 = range(10)
# r2 = range(1,10)
# r3 = range(1,10,2)
# 帮助创建连续的数字,或通过设置步长来指定不连续
# v = range(0, 100, 5)
# for item in v:
# print(item)