类型错误：解析器必须是字符串或字符流，而不是日期时间

Question

我试图让一个网页显示数据库中列出的所有即将上映的节目，以及分别存储在场地和艺术家表中的关于每个节目的一堆信息。我查询 Show 表，然后为该结果中的每一行链接 Artist 和 Venue 表。因为错误有事情做与日期时间，我假设的错误是与任一if show.start_time > current_time:或"start_time": show.start_time但误差不拖住它在哪里。我尝试将 current_time 和 show.start_time 都转换为字符串，看看是否有效，但没有运气。我究竟做错了什么？

@app.route('/shows')
def shows():

  current_time = datetime.now()

  data = []

  allshows = Show.query.all()

  for show in allshows:
    artist = Artist.query.get(show.artist_id)
    venue = Venue.query.get(show.venue_id)

    if show.start_time > current_time:
      data.append({
        "venue_id": show.venue_id,
        "venue_name": venue.name,
        "artist_id": show.artist_id,
        "artist_name": artist.name,
        "artist_image_link": artist.image_link,
        "start_time": show.start_time
      })
 
  return render_template('pages/shows.html', shows=data)

如果有帮助，以下是与之相关的模型：

class Venue(db.Model):
    __tablename__ = 'venues'

    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String)
    city = db.Column(db.String(120))
    state = db.Column(db.String(120))
    address = db.Column(db.String(120))
    phone = db.Column(db.String(120))
    image_link = db.Column(db.String(500))
    facebook_link = db.Column(db.String(120))
    genres = db.Column(db.ARRAY(db.String))
    image_link = db.Column(db.String(500))
    facebook_link = db.Column(db.String(120))
    website = db.Column(db.String(300))
    seeking_talent = db.Column(db.Boolean)
    seeking_description = db.Column(db.String(120))
    shows = db.relationship('Show', backref='venue', lazy=True)

class Artist(db.Model):
    __tablename__ = 'artists'

    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String)
    city = db.Column(db.String(120))
    state = db.Column(db.String(120))
    phone = db.Column(db.String(120))
    genres = db.Column(db.String(120))
    image_link = db.Column(db.String(500))
    facebook_link = db.Column(db.String(120))
    website = db.Column(db.String(300))
    seeking_shows = db.Column(db.Boolean)
    seeking_description = db.Column(db.String(120))
    shows = db.relationship('Show', backref='artist', lazy=True)        

class Show(db.Model):
    __tablename__ = 'shows'

    id = db.Column(db.Integer, primary_key=True)
    artist_id = db.Column(db.Integer, db.ForeignKey('artists.id'), nullable = False)
    venue_id = db.Column(db.Integer, db.ForeignKey('venues.id'), nullable = False)
    start_time = db.Column(db.DateTime, nullable = False)

    def __repr__(self):
        return '<Show {} {}>'.format(self.artist_id, self.venue_id)

编辑：包括完整的追溯。

Traceback (most recent call last):
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/env/lib/python3.8/site-packages/flask/app.py", line 2464, in __call__
    return self.wsgi_app(environ, start_response)
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/env/lib/python3.8/site-packages/flask/app.py", line 2450, in wsgi_app
    response = self.handle_exception(e)
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/env/lib/python3.8/site-packages/flask/app.py", line 1867, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/env/lib/python3.8/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/env/lib/python3.8/site-packages/flask/app.py", line 2447, in wsgi_app
    response = self.full_dispatch_request()
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/env/lib/python3.8/site-packages/flask/app.py", line 1952, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/env/lib/python3.8/site-packages/flask/app.py", line 1821, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/env/lib/python3.8/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/env/lib/python3.8/site-packages/flask/app.py", line 1950, in full_dispatch_request
    rv = self.dispatch_request()
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/env/lib/python3.8/site-packages/flask/app.py", line 1936, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/app.py", line 547, in shows
    return render_template('pages/shows.html', shows=data)
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/env/lib/python3.8/site-packages/flask/templating.py", line 137, in render_template
    return _render(
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/env/lib/python3.8/site-packages/flask/templating.py", line 120, in _render
    rv = template.render(context)
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/env/lib/python3.8/site-packages/jinja2/environment.py", line 1090, in render
    self.environment.handle_exception()
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/env/lib/python3.8/site-packages/jinja2/environment.py", line 832, in handle_exception
    reraise(*rewrite_traceback_stack(source=source))
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/env/lib/python3.8/site-packages/jinja2/_compat.py", line 28, in reraise
    raise value.with_traceback(tb)
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/templates/pages/shows.html", line 1, in top-level template code
    {% extends 'layouts/main.html' %}
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/templates/layouts/main.html", line 103, in top-level template code
    {% block content %}{% endblock %}
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/templates/pages/shows.html", line 9, in block "content"
    <h4>{{ show.start_time|datetime('full') }}</h4>
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/app.py", line 101, in format_datetime
    date = dateutil.parser.parse(value)
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/env/lib/python3.8/site-packages/dateutil/parser.py", line 1168, in parse
    return DEFAULTPARSER.parse(timestr, **kwargs)
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/env/lib/python3.8/site-packages/dateutil/parser.py", line 556, in parse
    res, skipped_tokens = self._parse(timestr, **kwargs)
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/env/lib/python3.8/site-packages/dateutil/parser.py", line 675, in _parse
    l = _timelex.split(timestr)         # Splits the timestr into tokens
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/env/lib/python3.8/site-packages/dateutil/parser.py", line 192, in split
    return list(cls(s))
  File "/Users/ZEMEL/Dropbox (Personal)/Code/fyyurr/env/lib/python3.8/site-packages/dateutil/parser.py", line 60, in __init__
    raise TypeError('Parser must be a string or character stream, not '
TypeError: Parser must be a string or character stream, not datetime

编辑2：def格式化日期时间：

def format_datetime(value, format='medium'):
  date = dateutil.parser.parse(value)
  if format == 'full':
      format="EEEE MMMM, d, y 'at' h:mma"
  elif format == 'medium':
      format="EE MM, dd, y h:mma"
  return babel.dates.format_datetime(date, format)

app.jinja_env.filters['datetime'] = format_datetime

Answer 1

从回溯可以看出，在渲染模板期间引发了异常。日期格式过滤器

<h4>{{ show.start_time|datetime('full') }}</h4>

似乎只期望字符串值，并尝试将它们解析为datetime. 另一方面，您的模型使用正确的时间戳类型，因此该属性show.start_time已经是一个datetime实例。解决此不匹配的一种方法是更改​​格式过滤器以接受datetime值：

def format_datetime(value, format='medium'):
    # instead of just date = dateutil.parser.parse(value)
    if isinstance(value, str):
        date = dateutil.parser.parse(value)
    else:
        date = value
    ...