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I'm reading info in from a CSV to my django model, but it keeps throwing an ValueError: Cannot assign "'Sheffield United'": "Match.home_team" must be a "Team" instance. I can add data fine in the admin interface (perhaps obviously), but trying to do it programmatically gives me that error.

I had the same issue with 'League', and commented it out just to test - both the league ("E2") object and Team 'Sheffield United' exist in the database, as I added them to test that.

I then changed them to, for example home_team = Team.objects.get(id=row[2]) as per this answer.. I think that may have solved the initial problem, but I now get: ValueError: invalid literal for int() with base 10: 'Sheffield United', which is baffling as it's a string.

Models.py:

class League (models.Model):
    name = models.CharField(max_length=2)
    last_modified = models.CharField(max_length=50)
    def __unicode__(self):
        return unicode(self.name)

class Team(models.Model):
    team_name = models.CharField(max_length=50)
    league = models.ForeignKey(League)
    team_colour = models.CharField(max_length=6, null=True, blank=True)
    def __unicode__(self):
        return unicode (self.team_name)

class Match(models.Model):
    RESULT_CHOICES = (
        ('H', 'Home'),
        ('D', 'Draw'),
        ('A', 'Away'))
    league = models.ForeignKey(League)
    match_date = models.DateTimeField()
    home_team = models.ForeignKey(Team)
    away_team = models.CharField(max_length=50)
    full_time_home_goals = models.PositiveSmallIntegerField(blank=True, null=True)
    full_time_away_goals = models.PositiveSmallIntegerField(blank=True, null=True)
    full_time_result = models.CharField(max_length=1, choices=RESULT_CHOICES, blank=True, null=True)
    half_time_home_goals = models.PositiveSmallIntegerField(blank=True, null=True)
    half_time_away_goals = models.PositiveSmallIntegerField(blank=True, null=True)
    half_time_result = models.CharField(max_length=1, choices=RESULT_CHOICES,blank=True, null=True)
    home_shots = models.PositiveSmallIntegerField(blank=True, null=True)
    away_shots = models.PositiveSmallIntegerField(blank=True, null=True)
    home_shots_on_target = models.PositiveSmallIntegerField(blank=True, null=True)
    away_shots_on_target = models.PositiveSmallIntegerField(blank=True, null=True)
    home_corners = models.PositiveSmallIntegerField(blank=True, null=True)
    away_corners = models.PositiveSmallIntegerField(blank=True, null=True)
    home_yellow = models.PositiveSmallIntegerField(blank=True, null=True)
    away_yellow = models.PositiveSmallIntegerField(blank=True, null=True)
    home_red = models.PositiveSmallIntegerField(blank=True, null=True)
    away_red = models.PositiveSmallIntegerField(blank=True, null=True)
    def __unicode__(self):
        return unicode(self.home_team) + " v " + unicode(self.away_team) + " " + unicode(self.match_date)
    class Meta:
        verbose_name_plural = "Matches"

The management command that I'm using is: (right now I'm running it from the commandline to debug it, so have stripped the BaseCommand subclassing out of this code - it didn't affect the error I was seeing.) 

from django.core.management.base import BaseCommand, CommandError
import csv
import csvImporter
from core.models import Match

master_data = open ('/Users/chris/Dropbox/Django/gmblnew/data/testfile.csv', 'r') 
data = list(tuple(rec) for rec in csv.reader(master_data, delimiter=','))
from core.models import Match, League

for row in data:
    current_match = Match(
        league=row[0],
        match_date = row[1], 
        home_team = row[2],
        away_team = row[3],
        full_time_home_goals = row[4],
        full_time_away_goals = row[5],
        home_shots = row[10],
        away_shots = row[11],
        home_shots_on_target = row[12],
        away_shots_on_target = row[13],
        home_corners = row[16],
        away_corners = row[17],
        full_time_result = row[6],
    )
    print current_match

Original traceback (on 'must be an instance' error:)

Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/core/management/__init__.py", line 453, in execute_from_command_line
    utility.execute()
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/core/management/__init__.py", line 392, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/core/management/__init__.py", line 272, in fetch_command
    klass = load_command_class(app_name, subcommand)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/core/management/__init__.py", line 77, in load_command_class
    module = import_module('%s.management.commands.%s' % (app_name, name))
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/utils/importlib.py", line 35, in import_module
    __import__(name)
  File "/Users/chris/Dropbox/Django/gmblnew/core/management/commands/ImportCSV.py", line 24, in <module>
    full_time_result = row[6],
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/db/models/base.py", line 403, in __init__
    setattr(self, field.name, rel_obj)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/db/models/fields/related.py", line 405, in __set__
    self.field.name, self.field.rel.to._meta.object_name))
ValueError: Cannot assign "'Sheffield United'": "Match.home_team" must be a "Team" instance.

Most recent traceback: 

Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/core/management/__init__.py", line 453, in execute_from_command_line
    utility.execute()
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/core/management/__init__.py", line 392, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/core/management/__init__.py", line 272, in fetch_command
    klass = load_command_class(app_name, subcommand)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/core/management/__init__.py", line 77, in load_command_class
    module = import_module('%s.management.commands.%s' % (app_name, name))
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/utils/importlib.py", line 35, in import_module
    __import__(name)
  File "/Users/chris/Dropbox/Django/gmblnew/core/management/commands/ImportCSV.py", line 14, in <module>
    home_team = Team.objects.get(id=row[2]),
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/db/models/manager.py", line 143, in get
    return self.get_query_set().get(*args, **kwargs)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/db/models/query.py", line 379, in get
    clone = self.filter(*args, **kwargs)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/db/models/query.py", line 655, in filter
    return self._filter_or_exclude(False, *args, **kwargs)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/db/models/query.py", line 673, in _filter_or_exclude
    clone.query.add_q(Q(*args, **kwargs))
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1266, in add_q
    can_reuse=used_aliases, force_having=force_having)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1197, in add_filter
    connector)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/db/models/sql/where.py", line 71, in add
    value = obj.prepare(lookup_type, value)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/db/models/sql/where.py", line 339, in prepare
    return self.field.get_prep_lookup(lookup_type, value)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/db/models/fields/__init__.py", line 322, in get_prep_lookup
    return self.get_prep_value(value)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/db/models/fields/__init__.py", line 555, in get_prep_value
    return int(value)
ValueError: invalid literal for int() with base 10: 'Sheffield United'

At the moment, I'm reading in some initial data for testing, but manipulating CSVs into the database is something that I'll be doing regularly, so some guidance would be appreciated. (I've had a look at a couple of CSVImporter tools - right now, I don't want to use them, as I want to understand the guts of what I'm doing, and I feel like what I've written should suffice, if I can get past this problem.)

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2 回答 2

4

由于home_team是 a ForeignKey，它只能接受该模型的实例；您正在尝试向其传递一个字符串，该字符串是主队的名称，这就是此错误的含义：

ValueError: Cannot assign "'Sheffield United'": "Match.home_team" must be a "Team" instance.

在您的导入器脚本中，您需要搜索代表主队的对象，并将其指定为外键。您可以使用get_or_create来获取现有团队，或为团队名称创建新团队；像这样：

from django.core.management.base import BaseCommand, CommandError
import csv
import csvImporter
from core.models import Match

master_data = open ('/Users/chris/Dropbox/Django/gmblnew/data/testfile.csv', 'r') 
data = list(tuple(rec) for rec in csv.reader(master_data, delimiter=','))
from core.models import Match, League, Team

for row in data:
    league, _ = League.objects.get_or_create(name=row[0])
    home_team, _ = Team.objects.get_or_create(team_name=row[2], league=league)
    away_team, _ = Team.objects.get_or_create(team_name=row[3], league=league)
    current_match = Match(
        league = league,
        home_team = home_team,
        away_team = away_team,
        match_date = row[1], 
        full_time_home_goals = row[4],
        full_time_away_goals = row[5],
        home_shots = row[10],
        away_shots = row[11],
        home_shots_on_target = row[12],
        away_shots_on_target = row[13],
        home_corners = row[16],
        away_corners = row[17],
        full_time_result = row[6],
    )
    print current_match

这条线Team.objects.get_or_create(team_name=row[2])的意思是：

“尝试获取一个 Team_name 与 的值相同的 Team 对象 row[2]，如果不存在，则创建一个新的 Team 对象并返回它”

get_or_create将返回一个 2 元组，第二部分是一个布尔值，告诉您是创建了新项目还是检索了现有项目。由于我们只对第一部分感兴趣，我将代码更新为只使用实例并忽略第二个值。

于 2013-10-20T12:36:28.913 回答
1

试试home_team = Team.objects.get(team_name=row[2])。问题在于该Team.id字段是一个整数字段（由于没有primary_key定义任何字段，django 会自动创建一个整数id字段）并且您正在为其分配一个字符串。

于 2013-10-20T12:31:54.987 回答