Question

我环顾四周，并且我已经看到了一些我认为可以用于我自己的代码的解决方案，但似乎什么也没做。

我正在尝试从JSON文件中提取数据并将信息添加到数组中。然后，数组将用于将数据输入到我添加到数据库的多个对象中（我知道，这非常低效，但是我编写原始脚本的方式，我没有必要将对象添加到数据库中。我打算改变它。）

对象包含与之关联的日期时间。我使用Python的strptime函数将字符串转换为datetime对象。

在我的models.py中，我有一个日期时间的DateTimeField。

但是，当我尝试迁移时，出现以下错误：

TypeError: expected string or bytes-like object

以下是整个追溯：

Applying interactive_table.0016_auto_20161024_2259...Traceback (most recent call last):
  File "manage.py", line 22, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/andrewho/anaconda/lib/python3.5/site-packages/django/core/management/__init__.py", line 367, in execute_from_command_line
    utility.execute()
  File "/Users/andrewho/anaconda/lib/python3.5/site-packages/django/core/management/__init__.py", line 359, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/andrewho/anaconda/lib/python3.5/site-packages/django/core/management/base.py", line 294, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/Users/andrewho/anaconda/lib/python3.5/site-packages/django/core/management/base.py", line 345, in execute
    output = self.handle(*args, **options)
  File "/Users/andrewho/anaconda/lib/python3.5/site-packages/django/core/management/commands/migrate.py", line 204, in handle
    fake_initial=fake_initial,
  File "/Users/andrewho/anaconda/lib/python3.5/site-packages/django/db/migrations/executor.py", line 115, in migrate
    state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "/Users/andrewho/anaconda/lib/python3.5/site-packages/django/db/migrations/executor.py", line 145, in _migrate_all_forwards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "/Users/andrewho/anaconda/lib/python3.5/site-packages/django/db/migrations/executor.py", line 244, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/Users/andrewho/anaconda/lib/python3.5/site-packages/django/db/migrations/migration.py", line 129, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "/Users/andrewho/anaconda/lib/python3.5/site-packages/django/db/migrations/operations/fields.py", line 84, in database_forwards
    field,
  File "/Users/andrewho/anaconda/lib/python3.5/site-packages/django/db/backends/sqlite3/schema.py", line 231, in add_field
    self._remake_table(model, create_fields=[field])
  File "/Users/andrewho/anaconda/lib/python3.5/site-packages/django/db/backends/sqlite3/schema.py", line 113, in _remake_table
    self.effective_default(field)
  File "/Users/andrewho/anaconda/lib/python3.5/site-packages/django/db/backends/base/schema.py", line 221, in effective_default
    default = field.get_db_prep_save(default, self.connection)
  File "/Users/andrewho/anaconda/lib/python3.5/site-packages/django/db/models/fields/__init__.py", line 755, in get_db_prep_save
    prepared=False)
  File "/Users/andrewho/anaconda/lib/python3.5/site-packages/django/db/models/fields/__init__.py", line 1438, in get_db_prep_value
    value = self.get_prep_value(value)
  File "/Users/andrewho/anaconda/lib/python3.5/site-packages/django/db/models/fields/__init__.py", line 1417, in get_prep_value
    value = super(DateTimeField, self).get_prep_value(value)
  File "/Users/andrewho/anaconda/lib/python3.5/site-packages/django/db/models/fields/__init__.py", line 1275, in get_prep_value
    return self.to_python(value)
  File "/Users/andrewho/anaconda/lib/python3.5/site-packages/django/db/models/fields/__init__.py", line 1378, in to_python
    parsed = parse_datetime(value)
  File "/Users/andrewho/anaconda/lib/python3.5/site-packages/django/utils/dateparse.py", line 93, in parse_datetime
    match = datetime_re.match(value)

供参考，这是我的views.py：

def getInfo(counter, hekJSON):
    for counter in range(len(hekJSON["Events"])):
        dateAndTimeHEK.append(convertTimes(hekJSON["Events"][counter]["startTime"]))
        xcen.append(float("%.2f" % hekJSON["Events"][counter]["xCen"]))
        ycen.append(float("%.2f" % hekJSON["Events"][counter]["yCen"]))
        xfov.append(float("%.2f" % hekJSON["Events"][counter]["raster_fovx"]))
        yfov.append(float("%.2f" % hekJSON["Events"][counter]["raster_fovy"]))
        sciObj.append(hekJSON["Events"][counter]["sciObjectives"])


def convertTimes(dateAndTime):
    dateTime = datetime.datetime.strptime(dateAndTime, '%Y-%m-%d %H:%M:%S')
    return dateTime

def display(request):
    noaaNmbr='11809'
    #for right now, this is the only active region that I'm pulling data for. When I get the graph up and running, I will make it more interactive for the user so that he can 

    urlData = "http://www.lmsal.com/hek/hcr?cmd=search-events3&outputformat=json&instrument=IRIS&noaanum="+ noaaNmbr +"&hasData=true"

    webUrl = urlopen(urlData)
    counter = 0
    data = webUrl.read().decode('utf-8')
    hekJSON = json.loads(data)
    getInfo(counter, hekJSON)

    for i in range(getNumberOfEntries(hekJSON)):
        observation = models.HEK_Observations(noaaNmbr=noaaNmbr, dateAndTime=dateAndTimeHEK[i], xcen=xcen[i], ycen=ycen[i], xfov=xfov[i], yfov=yfov[i], sciObj=sciObj[i])
        observation.save()

    return render(request, 'template.html', {'obj': models.HEK_Observations.objects.filter(noaaNmbr=noaaNmbr)})

这是我的models.py：

from django.db import models
import datetime

class HEK_Observations(models.Model):
    dateAndTime = models.DateTimeField(max_length = 40, default = None, verbose_name = 'Date And Time')

这是我的urls.py:

from django.conf.urls import url
from . import views

urlpatterns = [
    # /table/
    url(r'^$', views.display, name='display'),
]

类似问题的其他解决方案已经说过问题在于我的默认值。但是，当我没有设置默认值（如代码中所示）时，我仍然会得到相同的错误。

Answer 1

您在迁移时遇到了错误，因此我猜测您的日期时间字段是一个字符串，并且您已将其设为日期时间字段。问题似乎是您的迁移从这些文本元素转变为日期。您可能需要清理数据库，转储数据库（如果是测试数据）或制作更好的手动迁移脚本。

让迁移变得不完美 - 如果您拥有不同格式的现有数据，则必须制作代码以将数据修改为新格式并保留信息。

如果它只是测试数据（通常是这样），你可以直接截断表 - 现在手动删除，（甚至删除数据库），或者在迁移脚本中使用一行。

其糟糕的形式是删除＆＃39;你的迁移文件并重新制作（特别是如果你有多个用户），但是如果你有很好的控制过程，可以做一些干净的版本（即每个版本一次迁移）。

Answer 2

您应该删除迁移文件，然后再次运行迁移

Python / Django - 期望字符串或类字节对象

2 个答案: