1 def hello_world():

2     intro = ''  #这里为空或None时候会显示默认值。

3     return render_template('index.html',intro=intro)

4

5 {{ intro | default('此人很懒，没留下信息。',boolean =True)}}
或者：

{{ intro or '此人很懒，没留下信息。' }}

 1 @app.route('/')

 2 def hello_world():

 3     intro = 'hello,world!what are you...?'

 4

 5     return render_template('index.html',intro=intro)

 6

 7 @app.template_filter('my_cut')

 8 def cut(value):

 9     value = str(value).replace('hello','Hi')

10     return value

11

12

13 {{ intro | my_cut }}

 1 @app.route('/')

 2 def hello_world():

 3     intro = 'hello,world!what are you...?'

 4     create_time = datetime(2019,8,15,12,32,15)  #设置任意时间

 5     return render_template('index.html',intro=intro,create_time=create_time)

 6

 7 @app.template_filter('handle_time')  #设置过滤器名称

 8 def handle_time(time):

 9     if isinstance(time,datetime):

10         now = datetime.now()

11         timestamp = (now - time).total_seconds()  #换算为秒

12         if timestamp < 60:

13             return '刚刚'

14         elif timestamp >= 60 and timestamp < 60* 60:

15             return "%s分钟前" %str(int(timestamp / 60))

16         elif timestamp >= 60 * 60 and timestamp < 60 * 60 * 24:

17             return "%s小时前" % str(int(timestamp / 60 / 60))

18         elif timestamp > 60 * 60 * 24:

19             return time.strftime('%Y/%m%d %H:%M')  #按照‘2019/0815 12:32’格式输出

20     else:

21         return time.strftime('%Y/%m%d %H:%M')

22

23

24 {{ create_time | handle_time }}