在python2中，这是有效的：
>>> try:
... pass
... except Exception as (e, b):
... pass
但在python3中，我收到语法错误：
>>> try:
... pass
... except Exception as (e, b):
File "<stdin>", line 3
except Exception as (e, b):
^
SyntaxError: invalid syntax
如何在python 3中捕获tuple（）异常？
编辑：
经过一些投入，我做了一些挖掘工作，我将改变这个问题：
我在python2中看到了这个语法：
try:
pass
except Exception, (num, msg):
pass
我不知道这是做什么的，但语法在python2中是有效的。 这是python3中的语法错误，所以我将其转换为：
try:
pass
except Exception as (num, msg):
pass
哪个仍是语法错误。那么，我想现在的问题是，第一种语法的初衷是什么，现在如何在python3中完成？
答案 0 :(得分：1)
在Python 2中，有效的语法但被捕获的public class MainActivity extends AppCompatActivity implements ZXingScannerView.ResultHandler {
private static final int REQUEST_CAMERA = 1;
final static String serverUrl = "";
private ZXingScannerView scannerView;
String res;
ImageButton img;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//setContentView(R.layout.activity_main);
Log.e("OnCreate", "OnCreated");
//ZXingScannerView zxing=(ZXingScannerView)findViewById(R.id.zxscan);
scannerView = (ZXingScannerView) findViewById(R.id.zxscan);
img=(ImageButton)findViewById(R.id.img1);
//scannerView.setResultHandler(this);
//scannerView.startCamera();
//zxing.addView(scannerView);
//setContentView(scannerView);
int currentapiVersion = android.os.Build.VERSION.SDK_INT;
if (currentapiVersion >= android.os.Build.VERSION_CODES.M) {
if (checkPermission()) {
Log.e("M", "Permission");
Toast.makeText(getApplicationContext(), "Permission already granted", Toast.LENGTH_LONG).show();
} else {
Log.e("R", "Permission");
requestPermission();
}
}
}
private boolean checkPermission() {
return (ContextCompat.checkSelfPermission(getApplicationContext(), CAMERA) == PackageManager.PERMISSION_GRANTED);
}
private void requestPermission() {
ActivityCompat.requestPermissions(this, new String[]{CAMERA}, REQUEST_CAMERA);
}
public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
switch (requestCode) {
case REQUEST_CAMERA:
if (grantResults.length > 0) {
Log.e("Successfull", "Success");
boolean cameraAccepted = grantResults[0] == PackageManager.PERMISSION_GRANTED;
if (cameraAccepted) {
Log.e("accpt", "Accpt");
Toast.makeText(getApplicationContext(), "Permission Granted, Now you can access camera", Toast.LENGTH_LONG).show();
} else {
Log.e("ntaccpt", "Not Acpt");
Toast.makeText(getApplicationContext(), "Permission Denied, You cannot access and camera", Toast.LENGTH_LONG).show();
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (shouldShowRequestPermissionRationale(CAMERA)) {
showMessageOKCancel("You need to allow access to both the permissions",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
requestPermissions(new String[]{CAMERA},
REQUEST_CAMERA);
}
}
});
return;
}
}
}
}
break;
}
}
private void showMessageOKCancel(String message, DialogInterface.OnClickListener okListener) {
new android.support.v7.app.AlertDialog.Builder(MainActivity.this)
.setMessage(message)
.setPositiveButton("OK", okListener)
.setNegativeButton("Cancel", null)
.create()
.show();
}
@Override
public void onResume() {
super.onResume();
int capi = android.os.Build.VERSION.SDK_INT;
if (capi >= android.os.Build.VERSION_CODES.M) {
if (checkPermission()) {
if (scannerView == null) {
scannerView = new ZXingScannerView(this);
setContentView(scannerView);
}
scannerView.setResultHandler(this);
scannerView.startCamera();
} else {
requestPermission();
}
}
}
@Override
public void onDestroy() {
super.onDestroy();
scannerView.stopCamera();
scannerView = null;
}
@Override
public void handleResult(final Result result) {
res = result.getText();
Log.d("Scanner Result", result.getText());
Log.d("Scanner Result", result.getBarcodeFormat().toString());
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("Scan Result");
builder.setPositiveButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
scannerView.resumeCameraPreview(MainActivity.this);
}
});
builder.setNeutralButton("Send", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
GetText();
scannerView.resumeCameraPreview(MainActivity.this);
}
});
builder.setMessage(result.getText());
AlertDialog alert = builder.create();
alert.show();
}
public void GetText() //throws UnsupportedEncodingException
{
String data = res;
String text = "";
BufferedReader reader = null;
Log.e("Datafirst", data);
String requesturi = serverUrl + data;
// Send data
try {
URL url = new URL(requesturi);
Log.e("DataSecond", requesturi);
if (Build.VERSION.SDK_INT > 9) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
}
URLConnection conn = url.openConnection();
conn.setDoOutput(true);
OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
wr.write(data);
wr.flush();
Log.e("Data Third", data);
reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
StringBuilder sb = new StringBuilder();
String line = null;
Toast.makeText(MainActivity.this, "Readed Successfully", Toast.LENGTH_SHORT).show();
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
Toast.makeText(MainActivity.this, "Readed Successfully", Toast.LENGTH_SHORT).show();
}
text = sb.toString();
} catch (Exception ex) {
Log.e("Exceptionio", "Error", ex);
ex.printStackTrace();
} finally {
try {
reader.close();
Log.e("Closed", "Closed");
} catch (Exception ex) {
Log.e("Except2", "Error", ex);
ex.printStackTrace();
}
}
Log.e("setText", data);
}
}
不是元组，因此如果您实际遇到<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<me.dm7.barcodescanner.zxing.ZXingScannerView
android:id="@+id/zxscan"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<ImageButton
android:id="@+id/img1"
android:layout_marginBottom="15dp"
android:layout_centerHorizontal="true"
android:layout_alignParentBottom="true"
android:src="@drawable/imgbut"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</RelativeLayout>
，它仍然会失败：
Exception所以你想要的只是：
Exception