python - 根据错误显示定制的异常消息

Question

我希望我的代码显示一条自定义错误消息，该消息取决于它遇到的错误类型。

from .forms import NameForm, IdForm
from django.shortcuts import render
from django.http import HttpResponse, HttpResponseRedirect
from django.contrib import messages
from client_storage import insert
import mysql.connector.errors
from mysql.connector.errors import Error
import MySQLdb


def sign_in(request):
        #we need to handle all the data that was just typed, we'll add a condition for that
        if request.method == "POST":
            #here will construct the form with the POST data
            form = NameForm(request.POST)
            #the next part is to check that the information submitted is valid
            if form.is_valid():
                post = form.save()
                post.save()
                return HttpResponse(post.question_text)
            else:
                return HttpResponse("Form is invalid")
        else:
            form = NameForm()
        return render(request, 'checkin/base.html', {'form': form})

    #this view will be the sign-up view, where new clients will be given new ID numbers for training

def sign_up(request):

    if request.method == "POST":
        form = IdForm(request.POST)
        if form.is_valid():
            post = form.save()
            post.save()
            ID = post.id_text
            #we'll call an external function that checks membership of the users input in the database
            # query is the first element of the tuple that is returned from insert()
            query = insert(post.id_text)
            if query == 1062:
                messages.add_message(request, messages.INFO, 'Already taken ')
                return HttpResponseRedirect('sign_up')
            if query == 1054:
                messages.add_message(request, messages.INFO, 'Invalid input')
                return HttpResponseRedirect('sign_up')
            else:
                messages.add_message(request, messages.INFO, 'Thank you for signing up!')
                return HttpResponseRedirect('sign_up')

            # if the user enters a number that is already in use raise an 'duplicate' error
            # Capture the exception here
        else:
            return HttpResponse('That text is invalid')
    else:
        form = IdForm()
    return render(request, 'checkin/base.html', {'form': form})

For the `except` block I'm trying to figure out how to display either "Already taken" or "Invalid input" depending on the error code. However only "Already taken" ever appears. I feel like the problem is that the exception is being thrown before it even gets to the `if` clauses?

我正在使用另一个文件进行 INSERT 过程:

import MySQLdb
import mysql.connector
from mysql.connector import errorcode
from django.contrib import messages

#Use a function to insert new information into the database

def insert(info):
    #open a connection
    db = MySQLdb.connect('localhost','root','password', 'CLIENTS')
    #prepare a cursor
    cursor = db.cursor()
    #prepare SQL query
    sql = "INSERT INTO clients(ID) VALUES (%s)" % info

    try:
        #execute the command
        cursor.execute(sql)
        #commit changes to the database
        print 'success'
        db.commit()
    except MySQLdb.Error as e:
        #return the first element in the tuple that contains the error message, which will be the errorcode
         if e[0] == 1062:
            return e[0]
         if e[0] == 1054:
            return e[0]

    #disconnect from server
    db.close()

编辑问题似乎是我使用mysql.connector.error而不是MySQLdb.Error。 mysql网站似乎只使用前者。似乎关于后者的官方文档并不多，但幸运的是我找到了 this site.我更改了代码，以便 sign_in View 将从外部 insert 函数接收返回的信息，然后采取相应的操作。

Answer 1

就像 @wwii 在评论中所说的那样，您需要编辑 try ... except block 才能捕获异常。请参阅documentations的此页.

此外，在您的实际代码中 Error(errno=1062) 始终返回一个非零字符串，该字符串验证您的 if 语句。这就是为什么您总是收到已采取消息的原因。

为了解决这个问题，您应该将代码修改为如下示例:

# What you need to import
import mysql.connector
from mysql.connector import errorcode

try:
    insert(post.id_text)
    messages.add_message(request, messages.INFO, 'Thank you for signing up ')
    return HttpResponseRedirect('sign_in')

# Catch the error exception
except mysql.connector.Error as err:
    # Error code 1062: https://dev.mysql.com/doc/refman/5.6/en/error-messages-server.html#error_er_dup_entry
    if err.errno == errorcode.ER_DUP_ENTRY:
        messages.add_message(request, messages.INFO, "Already taken") 
        return HttpResponseRedirect('sign_up')

    # Error code 1054: https://dev.mysql.com/doc/refman/5.6/en/error-messages-server.html#error_er_bad_field_error
    if err.errno == errorcode.ER_BAD_FIELD_ERROR:
        messages.add_message(request, messages.INFO, "Invalid input")
        return HttpResponseRedirect('sign_up')

编辑:

您编辑的答案在 Python2 和 Python3 中都是正确的。

否则，如果您使用的是Python2，您可以执行类似的操作。

try:
    #execute the command
    cursor.execute(sql)
    #commit changes to the database
    print 'success'
    db.commit()
except MySQLdb.Error, e:
     if e.args[0] == 1062 or e.args[0] == 1054:
        # e.args[0] is the error code in int format
        # e.args[1] is the complete error message in str format
        return e.args[1]
     else:
        # I didn't test all the cases, but this message
        # can save you more time during the debug later
        # if your code catch another error code rather than 1062 or 1054
        return "Something odd happened"

您也可以执行类似的操作(此示例如果对 Python2 和 Python3 均有效):

try:
    #execute the command
    cursor.execute(sql)
    #commit changes to the database
    print 'success'
    db.commit()
except MySQLdb.Error as e:
     if e[0] == 1062 or e[0] == 1054:
        # e[0] is the error code in int format
        # e[1] is the complete error message in str format
        return e[1]
     else:
        # Good for the debug
        return "Something odd happened"