{#格式   值｜函数#}
{#    如果没有值，那么使用默认值#}
    <p>{{ bucunzai|default:'空的哦' }}</p>

{#    取出变量长度#}
    <q>{{ name }}--{{ name|length }}</q>

{#      文件大小转换成可读型  kb 自动转成bm、g、tb#}
    <p>文件大小{{ file_size|filesizeformat }}</p>

{#    切片 从指定位置到指定位 ，例：第3位到-2位#}
    <p>切片:{{ slice_str|slice:'3:-2' }}</p>

{#    把datetime取到的时间，转成指定格式#}
    <p>格式化：{{ now|date:'Y-m-d H:i:s' }}</p>

{#    如果后端内容包含标签，那么加上safe 才能转义（防止用户直接加script标签作弊）防XSS攻击#}
    <p>{{ h_html|safe }}</p>

{#    取摘要只显示一段，指定取长度后面...例：120个字符 #}
    <p>长文本：{{ p_str|truncatechars:12 }}</p>

class UserView(ListAPIView):
    """用户列表"""
    queryset = User.objects.all()
    serializer_class = UserSerializer
    filter_backends = (DjangoFilterBackend,)
    filter_class = UserMonthFilter  # 指定过滤类

class RobotFilter(django_filters.FilterSet):
    # 使用过滤：URL?created_start_time=2020_01-20&created_end_time=2020_01-21
    robot_id = django_filters.CharFilter(field_name='id')
    machine_id = django_filters.CharFilter(field_name='machine_id')
    city = django_filters.CharFilter(field_name='city')
    # lookup_expr（可选）为判断条件，field_name（必选）为模型类属性，created_time查询字符串
    created_time= django_filters.CharFilter(field_name='created_at', lookup_expr='startswith')
    created_start_time = django_filters.DateTimeFilter(field_name='created_at', lookup_expr='gt')
    created_end_time = django_filters.DateTimeFilter(field_name='created_at', lookup_expr='lt')
    problem_isnull = django_filters.BooleanFilter(field_name='problem', lookup_expr='isnull')
    name = django_filters.CharFilter(lookup_expr='iexact')  # iexact表示精确匹配, 并且忽略大小写
    author = django_filters.CharFilter(lookup_expr='icontains') #icontains表示模糊查询（包含），并且忽略大小写
    price = django_filters.NumberFilter(look_expr='exact')  #exact表示精确匹配
    task_res_state = django_filters.CharFilter(method="get_task_res_state")
    
    def get_task_res_state(self, queryset, *arg):
        if str(arg[1]) == "0":  # arg[1]=('task_res_state', '0')
            task_res = (1, 2, 3)
        else:
            task_res = (0, 4, 5, 6)
        print(task_res)
        queryset = queryset.filter(task_res__in=task_res)
        return queryset
    class Meta:
        model = Robot
        fields = ['robot_id', 'machine_id', "city", "created_start_time", "created_end_time", 'created_time',
                  'firmware_version', 'state', "robot_type", "hardware_version", "exist_map", 'task_res_state']