Python 实用宝典

Question 1

Using Jinja2, how do I format a date field? I know in Python I can simply do this:

print(car.date_of_manufacture.strftime('%Y-%m-%d'))

But how do I format the date in Jinja2?

Question 2

There are two ways to do it. The direct approach would be to simply call (and print) the strftime() method in your template, for example

{{ car.date_of_manufacture.strftime('%Y-%m-%d') }}

Another, sightly better approach would be to define your own filter, e.g.:

from flask import Flask
import babel

app = Flask(__name__)

@app.template_filter()
def format_datetime(value, format='medium'):
    if format == 'full':
        format="EEEE, d. MMMM y 'at' HH:mm"
    elif format == 'medium':
        format="EE dd.MM.y HH:mm"
    return babel.dates.format_datetime(value, format)

(This filter is based on babel for reasons regarding i18n, but you can use strftime too). The advantage of the filter is, that you can write

{{ car.date_of_manufacture|datetime }}
{{ car.date_of_manufacture|datetime('full') }}

which looks nicer and is more maintainable. Another common filter is also the “timedelta” filter, which evaluates to something like “written 8 minutes ago”. You can use babel.dates.format_timedelta for that, and register it as filter similar to the datetime example given here.

Question 3

Here’s the filter that I ended up using for strftime in Jinja2 and Flask

@app.template_filter('strftime')
def _jinja2_filter_datetime(date, fmt=None):
    date = dateutil.parser.parse(date)
    native = date.replace(tzinfo=None)
    format='%b %d, %Y'
    return native.strftime(format)

And then you use the filter like so:

{{car.date_of_manufacture|strftime}}

Question 4

I think you have to write your own filter for that. It’s actually the example for custom filters in the documentation: http://jinja.pocoo.org/docs/api/#custom-filters

Question 5

If you are dealing with a lower level time object (I often just use integers), and don’t want to write a custom filter for whatever reason, an approach I use is to pass the strftime function into the template as a variable, where it can be called where you need it.

For example:

import time
context={
    'now':int(time.time()),
    'strftime':time.strftime }  # Note there are no brackets () after strftime
                                # This means we are passing in a function, 
                                # not the result of a function.

self.response.write(jinja2.render_template('sometemplate.html', **context))

Which can then be used within sometemplate.html:

<html>
    <body>
        <p>The time is {{ strftime('%H:%M%:%S',now) }}, and 5 seconds ago it was {{ strftime('%H:%M%:%S',now-5) }}.
    </body>
</html>

Question 6

You can use it like this in template without any filters

{{ car.date_of_manufacture.strftime('%Y-%m-%d') }}

Question 7

Google App Engine users : If you’re moving from Django to Jinja2, and looking to replace the date filter, note that the % formatting codes are different.

The strftime % codes are here: http://docs.python.org/2/library/datetime.html#strftime-and-strptime-behavior

Question 8

in flask, with babel, I like to do this :

@app.template_filter('dt')
def _jinja2_filter_datetime(date, fmt=None):
    if fmt:
        return date.strftime(fmt)
    else:
        return date.strftime(gettext('%%m/%%d/%%Y'))

used in the template with {{mydatetimeobject|dt}}

so no with babel you can specify your various format in messages.po like this for instance :

#: app/views.py:36
#, python-format
msgid "%%m/%%d/%%Y"
msgstr "%%d/%%m/%%Y"

Question 9

There is a jinja2 extension you can use just need pip install (https://github.com/hackebrot/jinja2-time)

Python 实用宝典

如何在Jinja2中格式化日期？

问题：如何在Jinja2中格式化日期？

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