python之路第五天
字符串的应用（二）
expandtabs 断句16，不够16个，用空格补齐
s = "username\te-mail\tpassword\nxiaoming\t123@qq.com\t123456" v = s.expandtabs(16) print(v)
isalpha判断是否是字母，汉字
test = "asdf" v = test.isalpha() print(v)
test = "as2df" v = test.isalpha() print(v)
当前输入的是否是数字
isdecimal：只支持单纯的数字
isdigit：不仅支持数字而且还支持特殊符号的数字
isnumeric：不仅支持数字而且还支持特殊符号的数字，还支持中文的数字
test = "②" v1 = test.isdecimal() v2 = test.isdigit() v3 = test.isnumeric() print(v1,v2,v3)
test = "二" v1 = test.isdecimal() v2 = test.isdigit() v3 = test.isnumeric() print(v1,v2,v3)
test = "123" v1 = test.isdecimal() v2 = test.isdigit() print(v1,v2)
test = "aa123" v1 = test.isdecimal() v2 = test.isdigit() print(v1,v2)
字母 数字 下划线 ：标识符
判断该变量是否满足标识符规则
a = "_123" v = a.isidentifier() print(v)
a = "123" v = a.isidentifier() print(v)
isprintable：是否存在不可显示的字符
\t 制表符
\n 换行
test = "oiua\tsdfj" v = test.isprintable() print(v)
test = "oiuasdfj" v = test.isprintable() print(v)
判断字符串里是否全部都是空格
test = " " v = test.isspace() print(v)
test = "a b c d" v = test.isspace() print(v)
istitle：判断是否是标题
title：将字符转换为标题
何为标题？ 字符串 中的每个字符首字母是大写
test = "Hao hao xue xi Tian tian xiang shang " v1 = test.istitle() v2 = test.title() v3 = v2.istitle() print(v1) print(v2) print(v3)
join 将字符串中的每一个元素按照指定分隔符进行拼凑
test = "你是风儿我是沙" print(test) t = ' ' v = t.join(test)# 相同 v = ' '.join(test) print(v)
填充字符串
center：居中填充
ljust：左填充
rjust：右填充
zfill：默认填充的是0
test = "xiaoming" v1 = test.center(20,"*") v2 = test.ljust(20,"*") v3 = test.rjust(20,"*") v4 = test.zfill(20) print(v1) print(v2) print(v3) print(v4)
字符串大小写的判断与转换
test = "Xiaoming" v1 = test.islower() #判断是否全部是小写 v2 = test.lower() #转换为小写 print(v1, v2)
v1 = test.isupper() #判断是否全部是大写 v2 = test.upper() #转换为大写 print(v1, v2)
去除左右空格
test = " xiaoming " v1 = test.lstrip() v2 = test.rstrip() v3 = test.strip() print(v1) print(v2) print(v3)
去除\n \t
test = "\nxiaoming " v1 = test.lstrip() v2 = test.rstrip() v3 = test.strip() print(v1) print(v2) print(v3)
test = "\txiaoming " v1 = test.lstrip() v2 = test.rstrip() v3 = test.strip() print(test) print(v1) print(v2) print(v3)
移除指定字符
test = "xiaoming" v1 = test.lstrip('xi')#从左边移除指定的字符 v2 = test.rstrip('ng')#从右边移除指定的字符 v3 = test.strip('ng')#移除的字符必须是原字符串首尾且连续的子字符，如果没有首或尾的子字符，将不能移除 print(v1) print(v2) print(v3)
替换文字
v = "你是谁，风好大，我听不清" m = str.maketrans("你是风儿我是沙", "缠缠绵绵到天涯") new_v = v.translate(m) print(new_v)
下面开始讲解 灰 魔法 了解一下
#索引 ， 下标，获取字符串中的某个自字符 test = "alex" # v = test[0] # print(v) #切片 # v = test[0:-1] #0:1 0=< <1 # print(v) #len 获取当前字符串中有几个字符组成 # v = len(test) # print(v) li = [11,22,33,44,55,"asdf"] v1 = len("asdfgh") v2 = len(li)# 它计算的是用逗号隔开的分组元素 print(v1, v2)
test = "好好学习天天向上" # index = 0 # while index < len(test): # v = test[index] # print(v) # index += 1 # print('===============') #for 循环 # for 变量名 in 字符串： # print(变量名) for xm in test: print(xm)
字符串相加
字符串一旦创建，就不可修改
一旦修改或者拼接，都会重新生成新的字符串
name = "xiaoming" age = "18" info = name + age print(info)
原理及形成
替换
test = "alexalexalexalex" # v = test.replace("ex", 'bbb') # print(v)
test = "alexalexalexalex" v = test.replace("ex", 'bbb',2) # 2是从左到右替换的次数 print(v)
range 的基础用法
帮助创建连续的数字
输出0-100
v = range(100)# （0，100，5） for item in v: print(item)
练习《《《《《《《《《《
test = input("<<<") for item in range(0, len(test)): print(item, test[item])
