python的re

1.三种匹配方式
match—re.match 尝试从字符串的起始位置匹配一个模式，如果不是起始位置匹配成功的话，match()就返回none
search—re.search 扫描整个字符串并返回第一个成功的匹配
findall—在字符串中找到正则表达式所匹配的所有子串，并返回一个列表，如果没有找到匹配的，则返回空列表。

{
  "node": {
    "createdIndex": 285911008,
    "dir": false,
    "key": "/registry/ipsec/v1/default/bt2g2uh7hqddddka3e80",
    "modifiedIndex": 285911049,
    "ttl": 0,
    "value": "apiVersion: ipsec/v1nkind: Ipsecnmetadata:n  creationTimestamp: "2020-08-25T12:18:02Z"n  labels:n    channelId: E201202004080030n    linkName: bt1s06bmfjm8f18i7ongn    nodeName: HangZhou.xiasha.pop1.oldvm.vm3n    vxlanId: v204n  name: bt2g2uh7hqddddka3e80n  namespace: defaultn  uid: f2660a51-7a3f-4df0-8b47-fd51973a42c5nspec:n  ClientNetwork:n  - 172.16.2.0/24n  - 100.64.0.12/32n  Cmd: ""n  Eap: 291b643a-2f2f-480a-94d4-528051497298n  ErrMsg: ""n  IsMaster: falsen  Left: 100.64.0.19n  LeftId: 183.136.237.7n  LinkName: bt1s06bmfjm8f18i7ongn  Metric: 100n  NodeName: HangZhou.xiasha.pop1.oldvm.vm3n  Prepared: truen  Right: 100.64.0.20n  RightId: 10.201.0.189n  Secret: ba72c4e4-e7bc-475a-899e-de6abd4480c0n  UpdateTimestamp: 1598357884n  Vlan: 4n  VtiCreated: truen  VtiId: 45n  VxlanId: 204n"
  }
}

上面是res的返回结果，返回的（）中的内容，如果没有（），就匹配符合的内容

#匹配channelId: V501202007141416后的16位，可以换行匹配（re.MULTILINE)
comment = re.compile(r'channelId: (.{16})', re.MULTILINE)
sn = re.findall(comment,res['node']['value'])
sn_str = "".join(sn)
name_sn[i]=sn_str

2.Re库的贪婪匹配和最小匹配

Re库默认采取贪婪匹配,即输出匹配最长的子串

s = '{{"countryZh":"中国","provinceZh":"云南省","cityZh":"临沧市","countryEn":"China","provinceEn":"YunNan","cityEn":"LinCang"}: 10,{"countryZh":"中国","provinceZh":"内蒙古自治区","cityZh":"乌海市","countryEn":"China","provinceEn":"InnerMongoliaAutonomousRegion","cityEn":"WuHai"}: 3}'
d=re.findall('.*?cityZh":"(.*?)","countryEn',s)
结果：['临沧市', '乌海市']

如果是：
d=re.findall('.*cityZh":"(.*?)","countryEn',s)
结果：[ '乌海市']
如果是：
d=re.findall('.*?cityZh":"(.*)","countryEn',s)
['临沧市","countryEn":"China","provinceEn":"YunNan","cityEn":"LinCang"}: 10,{"countryZh":"中国","provinceZh":"内蒙古自治区","cityZh":"乌海市']

3.常用函数
1.sub替换：

#替换s中的hello为123,
s = "hello,world!!!"
print(re.sub(r'hello', "123", s))
#123,world!!!