根據(jù)圖書《python編程從入門到實(shí)踐》來操作，修改完models.py后，執(zhí)行命令python manage.py makemigrations learning_logs，就報(bào)錯(cuò)，求大神指點(diǎn)。

model.py 代碼

from django.db import models
class Topic(models.Model):
    """用戶學(xué)習(xí)的主題"""
    text = models.CharField(max_length = 200)
    date_added = models.DateTimeField(auto_now_add = True)

    def __str__ (self):
        """返回模型的字符串表示"""
        return self.text
    
class Entry(models.Model):
    """學(xué)到的有關(guān)某個(gè)主題的具體知識(shí)"""
    topic = models.ForeignKey(Topic)
    text = models.TextField()
    date_added = models.DateTimeField(auto_now_add = True)

    class Meta:
        verbose_name_plural = 'entries'

    def __str__(self):
        """返回模型的字符串表示"""
        return self.text[:50] + "..."

manage.py 代碼如下

#!/usr/bin/env python
import os
import sys

if __name__ == "__main__":
    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "learning_log.settings")
    try:
        from django.core.management import execute_from_command_line
    except ImportError as exc:
        raise ImportError(
            "Couldn't import Django. Are you sure it's installed and "
            "available on your PYTHONPATH environment variable? Did you "
            "forget to activate a virtual environment?"
        ) from exc
    execute_from_command_line(sys.argv)