Question

我在使用str.format（* args，** kwargs）时遇到了一些麻烦：

import datetime
from django.conf import settings
from django.core.management.base import BaseCommand
from django.core.mail import send_mass_mail
from django.contrib.auth.models import User
from django.db.models import Count


class Command(BaseCommand):

    def add_arguments(self, parser):
        parser.add_argument('--days', dest='days', type=int)

    def handle(self, *args, **options):
        emails = []
        subject = 'Enroll in a course'
        date_joined = datetime.date.today() - datetime.timedelta(days=options['days'])
        users = User.objects.annotate(course_count=Count('courses_joined'))
                    .filter(course_count=0, date_joined__lte=date_joined)
        for user in users:
            message = 'Dear {},\n\n What are you waiting for?'.format(user.first_name)
            emails.append((subject, message, settings.DEFAULT_FROM_EMAIL, [user.email]))
        send_mass_mail(emails)
        countEmails = len(emails)
        if countEmails:
            # self.stdout.write(countEmails)
            messageConsole = 'Sent {} reminders.' % format(int(countEmails))
            self.stdout.write(messageConsole)

运行命令“python manage.py enroll_reminder --days = 1”，那么错误来了：

Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/home/polar/.pyenv/versions/my_env/lib/python3.5/site-packages/django/core/management/__init__.py", line 354, in execute_from_command_line
    utility.execute()
  File "/home/polar/.pyenv/versions/my_env/lib/python3.5/site-packages/django/core/management/__init__.py", line 346, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/home/polar/.pyenv/versions/my_env/lib/python3.5/site-packages/django/core/management/base.py", line 394, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/home/polar/.pyenv/versions/my_env/lib/python3.5/site-packages/django/core/management/base.py", line 445, in execute
    output = self.handle(*args, **options)
  File "/home/polar/PythonLab/DjangoByExample/educa/students/management/commands/enroll_reminder.py", line 30, in handle
    messageConsole = 'Sent {} reminders.\n' % format(int(countEmails))
TypeError: not all arguments converted during string formatting

当我取消注释“self.stdout.write（countEmails）”时，又出现了另一个问题：

Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/home/polar/.pyenv/versions/my_env/lib/python3.5/site-packages/django/core/management/__init__.py", line 354, in execute_from_command_line
    utility.execute()
  File "/home/polar/.pyenv/versions/my_env/lib/python3.5/site-packages/django/core/management/__init__.py", line 346, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/home/polar/.pyenv/versions/my_env/lib/python3.5/site-packages/django/core/management/base.py", line 394, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/home/polar/.pyenv/versions/my_env/lib/python3.5/site-packages/django/core/management/base.py", line 445, in execute
    output = self.handle(*args, **options)
  File "/home/polar/PythonLab/DjangoByExample/educa/students/management/commands/enroll_reminder.py", line 29, in handle
    self.stdout.write(countEmails)
  File "/home/polar/.pyenv/versions/my_env/lib/python3.5/site-packages/django/core/management/base.py", line 111, in write
    if ending and not msg.endswith(ending):
AttributeError: 'int' object has no attribute 'endswith'

任何人都可以帮我看看我做错了吗？

谢谢！

Answer 1

您会混淆%和.format()格式

您可以这样做：

'Sent {} reminders'.format(countEmails)

或

'Sent %d reminders.' % countEmails

请注意countEmails已经是整数，无需拨打int(countEmails)。

Answer 2

您在旧的C风格字符串替换和新格式方法之间感到困惑。要么：

'Sent {} reminders.'.format(int(countEmails))

或

'Sent %s reminders.' % (int(countEmails),)

TypeError：并非django中字符串格式化期间转换的所有参数

2 个答案: