Question

我有2个列表，例如说

list1 = ['abc', 'xyz', 'cat', 'xyz', 'abc', 'pqr', 'dog']
list2 = ['xyz', 'dog', 'pqr', 'abc', 'cat']

我想通过用list1中元素的索引替换list2来创建新列表，例如

list3 = [3, 0, 4, 0, 3, 2, 1]

我应该在这里提到，我实际上是从list2那里得到list1的

list2 = list(set(list1))

因此list2没有重复项，并且具有list1的所有元素。

我想知道以Python方式获得list3的最快方法。到目前为止，我已经尝试了两种方法：

1>基本的.index方式

list3 = [list2.index(item) for item in list1]

2>使用以元素为键的字典和以值为索引的字典

d = {list2[i]:i for i in range(len(list2))}
list3 = [d[item] for item in list1]

Answer 1

如果您担心要查找重复值，只需先创建一个索引：

>>> idx={e:list2.index(e) for e in list2}

或者：

>>> idx={e:n for n,e in enumerate(list2)}

然后：

>>> [idx[e] for e in list1]
[3, 0, 4, 0, 3, 2, 1]

Answer 2

//---- Angular 2 Http Service Example ----
import {Injectable} from "@angular/core";
import {Http, Headers} from "@angular/http";
const AWS = require("aws-sdk");

@Injectable()
export class ApiGatewayService {

 constructor(private http:Http){

let creds = new AWS.CognitoIdentityCredentials({
  IdentityPoolId: "eu-west-1:xxx-xxxx-xxxxxxxx"
});

AWS.config.update({
  region: 'eu-west-1',
  credentials: creds
});

AWS.config.credentials.get((err) => {
  if(err) throw err;

  let httpRequest = new AWS.HttpRequest("https://xxxxx.execute-api.eu-west-1.amazonaws.com/v1/my/api", "eu-west-1");
  httpRequest.method = "POST";
  httpRequest.headers.host = "xxxxx.execute-api.eu-west-1.amazonaws.com";
  httpRequest.headers['Content-Type'] = "application/json";
  httpRequest.body = JSON.stringify({
    data: {
      username: 'foo',
      password: 'bar',
      applicationName: 'biz',
    }
  });

  let v4signer = new AWS.Signers.V4(httpRequest, "execute-api", true);
  v4signer.addAuthorization(AWS.config.credentials, AWS.util.date.getDate());

  //Create a headers object from the AWS signed request
  let headers = new Headers();
  for(let key of Object.keys(httpRequest.headers)){
    headers.set(key, httpRequest.headers[key]);
  }
  headers.delete('host'); //Browser throws a warning if attempting to set host header
  this.http.post(httpRequest.endpoint.href, httpRequest.body, {
    method: httpRequest.method,
    search: httpRequest.endpoint.search,
    headers: headers
  }).subscribe((data)=>{
    console.log(data); //Success
  });
})
 }
}

python：用另一个列表中的项目索引替换列表项

2 个答案: