Question

尝试将 CharField 数据中的数据迁移到表格中的 FloatingField 。新的floatingField具有Null = True。在python manage.py migrate之后。我得到 ValueError：无法将字符串转换为float： 迁移文件如下所示。

def coordinates(apps, schema_editor):
    # We can't import the Person model directly as it may be a newer
    # version than this migration expects. We use the historical version.
    Restaurant = apps.get_model("foodspots", "Restaurant")
    for restaurant in Restaurant.objects.all():
        restaurant.lat_duplicate = restaurant.lat
        restaurant.lng_duplicate = restaurant.lng
        restaurant.save()


class Migration(migrations.Migration):

    dependencies = [
        ('foodspots', '0028_auto_20160211_1931'),
    ]

    operations = [
        migrations.RunPython(coordinates),
    ]

CharFields的值类似于10.787878。因为它们都是坐标。一些字段也有空值。如何将它保存在表格的FloatingField列中。数据库是postgres

Answer 1

您必须自己在迁移中进行转换：

for restaurant in Restaurant.objects.all():       
    restaurant.lat_duplicate = float(restaurant.lat)
    restaurant.lng_duplicate = float(restaurant.lng)
    restaurant.save()

请注意，如果您的字段为NULL或包含空字符串或字符串不是float的可接受表示形式，则必须正确处理这些情况：

for restaurant in Restaurant.objects.all():       
    # minimalistic error handling
    try:
        restaurant.lat_duplicate = float(restaurant.lat)
        restaurant.lng_duplicate = float(restaurant.lng)
    except (TypeError, ValueError) as e:
        print "invalid type or value for restaurant %s : %s" % (
            restaurant, e
            )
    else:   
        restaurant.save()

Django数据迁移类型转换问题

1 个答案: