正则表达式

每次想学习正则表达式看到给个表让去背诵，就放弃了，这次从一个实例来学习并在线验证。

先给出一个天气预报接口返回数据

{"reason":"查询成功!","result":{"city":"上海","realtime":{"temperature":"26","humidity":"94","info":"晴","wid":"00","direct":"北风","power":"0级","aqi":"65"},"future":[{"date":"2019-09-10","temperature":"25\/32℃","weather":"多云","wid":{"day":"01","night":"01"},"direct":"南风转东南风"},{"date":"2019-09-11","temperature":"25\/32℃","weather":"阴转多云","wid":{"day":"02","night":"01"},"direct":"东北风转东南风"},{"date":"2019-09-12","temperature":"25\/31℃","weather":"阴转多云","wid":{"day":"02","night":"01"},"direct":"东风转东南风"},{"date":"2019-09-13","temperature":"24\/31℃","weather":"多云","wid":{"day":"01","night":"01"},"direct":"东南风转东风"},{"date":"2019-09-14","temperature":"24\/29℃","weather":"小雨转多云","wid":{"day":"07","night":"01"},"direct":"东北风"}]},"error_code":0}

示例一:

匹配出最低温度

正则表达式:

temperature":"[\d]{0,2}[\W]{2}[\d]{0,2}

正则表达式讲解:

此表达式的意思是:匹配含有(temperature":"+零到两位数字+零到两位特殊字符+零到两位数字+℃)的字符串

'\d'  用来匹配数字

{0,2} 表示[ ]内的字符长度

\w 表示英文字母和数字和下划线[A-Za-z0-9_]]

\W非字母和数字

匹配结果:

'temperature":"25\/32℃',

'temperature":"25\/32℃',

'temperature":"25\/31℃',

'temperature":"24\/31℃',

'temperature":"24\/29℃'

示例二:

匹配风向

正则表达式:

direct":"[\u4e00-\u9fa5]{3,10}"

此表达式的意思是:匹配包含"direct":"+三到十个汉字的字符串"

 \u4e00-\u9fa5 :匹配中文字符

{3,10} :表示[ ]中字符长度为3到10

匹配结果:

direct":"南风转东南风"

direct":"东北风转东南风"

direct":"东风转东南风"

direct":"东南风转东风"

direct":"东北风"

但是如果我们这么写表达式:direct":"[\u4e00-\u9fa5]{3,10}? 得到的结果将是:

direct":"南风转

direct":"东北风

direct":"东风转

direct":"东南风

direct":"东北风

为什么呢?

这里的问号相当于表明{3,10}里面匹配最小值(即匹配3位),也就是匹配3位,不加问号则是匹配到最大值(即有多少匹配多少,超过10位,则匹配10位)

以上使用正则表达式进行了匹配，下面对常用正则语法做个总结

'\d'  用来匹配数字

\w 表示英文字母和数字和下划线[A-Za-z0-9_]]

\W非字母和数字

\u4e00-\u9fa5 :匹配中文字符

{} 限定字符长度 ，可以是个范围，也可以是具体的一个值

. :匹配除换行符（\n）外的其他所有字符

*：匹配前面的表达式0次或者n次

^:从字符串开头匹配

$:从字符串结尾匹配

|:多项之间选择一个  

(str):小括号里面的字符是且的关系，所以会匹配到所以‘str’

[str]:中括号里面的字符是或的关系，所以会匹配到所有 ‘s’或 ‘t’ 或 ‘r’