Python的字符串以及常见使用方法
字符串 str
必须要记住的方法：
1.join：将字符串中的每个元素按照指定分隔符进行拼接
test = "你是风儿我是沙" print(test) # # t = ' ' v = "_".join(test) print(v)
2.split：分割为指定个数,还有rsplit()
test = "absjsjdfjs" v = test.split('s',2) print(v)
3.find：从开始往后找，找到第一个之后，获取其未知
# > 或 >= test = "alexalex" # 未找到 -1 v = test..find('ex') print(v)
4.strip：移除指定字符串，默认移除空格、回车、制表符（\t \n）
# 有限最多匹配
# test = "xa"
# # v = test.lstrip('xa')
# v = test.rstrip('9lexxexa')
# # v = test.strip('xa')
# print(v)
5.upper：转换为大写
6.lower：转换为小写
###########################################
# 1 首字母大写
# test = "aLex"
# v = test.capitalize()
# print(v)
# 2 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 设置宽度，并将内容居中
# 20 代指总长度
# * 空白未知填充，一个字符，可有可无
# v = test.center(20,"中")
# print(v)
# test = "alex"
# v = test.ljust(20,"*")
# print(v)
# test = "alex"
# v = test.rjust(20,"*")
# print(v)
# test = "alex"
# v = test.zfill(20)
# print(v)
# 4 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)
# 欠
# encode
# decode
# 5
# 以什么什么结尾
# 以什么什么开始
# test = "alex"
# v = test.endswith('ex')
# v = test.startswith('ex')
# print(v)
# 6 expandtabs,断句20，
# test = "username\temail\tpassword\nlaiying\tying@q.com\t123\nlaiying\tying@q.com\t123\nlaiying\tying@q.com\t123"
# v = test.expandtabs(20)
# print(v)
# 7 从开始往后找，找到第一个之后，获取其未知
# > 或 >=
# test = "alexalex"
# 未找到 -1
# v = test.find('ex')
# print(v)
# 8 index找不到，报错 忽略
# test = "alexalex"
# v = test.index('8')
# print(v)
# 9 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='alex',a=19)
# print(v)
# test = 'i am {0}, age {1}'
# print(test)
# v = test.format('alex',19)
# print(v)
# 10 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": 'alex', "a": 19})
# 11 字符串中是否只包含 字母和数字
# test = "123"
# v = test.isalnum()
# print(v)
# str
# 12 是否是字母，汉子
# test = "as2df"
# v = test.isalpha()
# print(v)
# 13 当前输入是否是数字
# test = "二" # 1，②
# v1 = test.isdecimal()
# v2 = test.isdigit()
# v3 = test.isnumeric()
# print(v1,v2,v3)
# 14 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 判断是否全部是空格
# test = ""
# v = test.isspace()
# print(v)
# 16 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 ***** 将字符串中的每一个元素按照指定分隔符进行拼接
# test = "你是风儿我是沙"
# print(test)
# # t = ' '
# v = "_".join(test)
# print(v)
# 18 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
# 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 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 分割为三部分
# test = "testasdsddfg"
# v = test.partition('s')
# print(v)
# v = test.rpartition('s')
# print(v)
# 22 分割为指定个数
# v = test.split('s',2)
# print(v)
# test.rsplit()
# 23 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 以xxx开头，以xx结尾
# test = "backend 1.1.1.1"
# v = test.startswith('a')
# print(v)
# test.endswith('a)
# 25 大小写转换
# test = "aLex"
# v = test.swapcase()
# print(v)
# 26 字母，数字，下划线 ： 标识符 def class
# a = "def"
# v = a.isidentifier()
# print(v)
# 27 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)
###################### 7个基本魔法 ######################
# join # '_'.join("asdfasdf")
# split
# find
# strip
# upper
# lower
# replace
###################### 4个灰魔法 ######################
# test = "郑建文妹子有种冲我来"
# 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 = "郑建文妹子有种冲我来"
# 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] # 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)
# 注意：
# len("asdf")
# for循环
# 索引
# 切片
# 五、获取连续或不连续的数字，
# Python2中直接创建在内容中
# 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,通过设置步长来指定不连续
# v = range(0, 100, 5)
#
# for item in v:
# print(item)
##### 练习题：根据用户输入的值，输出每一个字符以及当前字符所在的索引位置 #####
# test = input(">>>")
# for item in test:
# print(item)
# 将文字 对应的索引打印出来：
# test = input(">>>")
# print(test) # test = qwe test[0] test[1]
# l = len(test) # l = 3
# print(l)
#
# r = range(0,l) # 0,3
# for item in r:
# print(item, test[item]) # 0 q,1 w,2 e
# test = input(">>>")
# for item in range(0, len(test)):
# print(item, test[item])
###################### 1个深灰魔法 ######################
# 字符串一旦创建，不可修改
# 一旦修改或者拼接，都会造成重新生成字符串
# name = "zhengjianwen"
# age = "18"
#
# info = name + age
# print(info)
列表 list
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元祖 tuple
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字典 dict
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布尔值 bool
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