[求助帖] Python 生成数字签名

对方提供的写法是 Java 和 PHP，我想把他变成 Python 的，哪位大神帮忙指点一下。

Java 的写法

import org.apache.commons.codec.binary.Base64;
import java.security.KeyFactory;
import java.security.PrivateKey;
import java.security.Signature;
import java.security.spec.PKCS8EncodedKeySpec;

public class SHA256WithRSAAlgo {
  private static String consumerId = "b68d2a72...."; // Trimmed for security reason
  private static String baseUrl = "https://api-gateway.walmart.com/v3/feeds";
  private static String privateEncodedStr = "MIICeAIBADANBgkqhkiG9w0BAQEFAA......";       //Trimmed for security reasons
  public static void main(String[] args) {
    String httpMethod = "GET";
    String timestamp = String.valueOf(System.currentTimeMillis());
    String stringToSign = consumerId + "\n" + baseUrl + "\n" + httpMethod + "\n" + timestamp + "\n";
    String signedString = SHA256WithRSAAlgo.signData(stringToSign, privateEncodedStr);
    System.out.println("Signed String: " + signedString);
  }
  public static String signData(String stringToBeSigned, String encodedPrivateKey) {
    String signatureString = null;
    try {
      byte[] encodedKeyBytes = Base64.decodeBase64(encodedPrivateKey);
      PKCS8EncodedKeySpec privSpec = new PKCS8EncodedKeySpec(encodedKeyBytes);
      KeyFactory kf = KeyFactory.getInstance("RSA");
      PrivateKey myPrivateKey = kf.generatePrivate(privSpec);
      Signature signature = Signature.getInstance("SHA256withRSA");
      signature.initSign(myPrivateKey);
      byte[] data = stringToBeSigned.getBytes("UTF-8");
      signature.update(data);
      byte[] signedBytes = signature.sign();
      signatureString = Base64.encodeBase64String(signedBytes);
    } catch (Exception e) {
      e.printStackTrace();
    }
    return signatureString;
  }
}

PHP 的写法

$URL = //Walmart API URL along with path and query parameters
$RequestMethod = //Request method type i.e GET, POST
$Timestamp = round(microtime(true) * 1000); //Current system timestamp
function _GetWalmartAuthSignature($URL, $RequestMethod, $Timestamp) {
  $WalmartPrivateKey = //Your Walmart Private Key;
  $WalmartConsumerID = //Your Walmart Comsumer Id;
  // CONSTRUCT THE AUTH DATA WE WANT TO SIGN
  $AuthData = $WalmartConsumerID."\n";
  $AuthData .= $URL."\n";
  $AuthData .= $RequestMethod."\n";
  $AuthData .= $Timestamp."\n";
  // GET AN OPENSSL USABLE PRIVATE KEY FROMM THE WARMART SUPPLIED SECRET
  $Pem = _ConvertPkcs8ToPem(base64_decode($WalmartPrivateKey));
  $PrivateKey = openssl_pkey_get_private($Pem);
  // SIGN THE DATA. USE sha256 HASH
  $Hash = defined("OPENSSL_ALGO_SHA256") ? OPENSSL_ALGO_SHA256 : "sha256";
  if (!openssl_sign($AuthData, $Signature, $PrivateKey, $Hash))
  { // IF ERROR RETURN NULL return null; }
    //ENCODE THE SIGNATURE AND RETURN
    return base64_encode($Signature);
  }
  function _ConvertPkcs8ToPem($der)
  {
    static $BEGIN_MARKER = "-----BEGIN PRIVATE KEY-----";
    static $END_MARKER = "-----END PRIVATE KEY-----";
    $key = base64_encode($der);
    $pem = $BEGIN_MARKER . "\n";
    $pem .= chunk_split($key, 64, "\n");
    $pem .= $END_MARKER . "\n";
    return $pem;
  }
}