librelist archives

How do I return a list as a variable in Python and use in Jinja2?

From:

Alasdair Macmillan

Date:

2010-10-19 @ 16:21

I am a real beginner programmer and I am trying to do something in Python 
but I'm stuck. I have a list of users in Couchdb (using python couchdb 
library & Flask framework) who have a username (which is the _id) and 
email. I want to use the list of email addresses in a select box in a 
jinja2 template.

My first problem is how to access the email addresses. If I do:

    for user in db:
        doc = db[user]
        emails = doc['email']
        print options

I get:

    email@domain.com
    otheremail@otherdomain.com
    yetanotheremail@yetanotherdomain.com


So I can get my list of emails. But where my brutal inexperience is 
showing up is that I don't know how to then use them. The list only exists
in the for loop. How do I return that list as a useable list of variables?
And how do I then make that list appear in my jinja2 template in an option
dropdown. I guess I need a function but I am a green programmer.

Would so appreciate help.

On Tue, 2010-10-19 at 17:21 +0100, Alasdair Macmillan wrote:
> I am a real beginner programmer and I am trying to do something in 
Python but I'm stuck. I have a list of users in Couchdb (using python 
couchdb library & Flask framework) who have a username (which is the _id) 
and email. I want to use the list of email addresses in a select box in a 
jinja2 template.
> 
> My first problem is how to access the email addresses. If I do:
> 
>     for user in db:
>         doc = db[user]
>         emails = doc['email']
>         print options
> 
> I get:
> 
>     email@domain.com
>     otheremail@otherdomain.com
>     yetanotheremail@yetanotherdomain.com
> 
> 
> So I can get my list of emails. But where my brutal inexperience is 
showing up is that I don't know how to then use them. The list only exists
in the for loop. How do I return that list as a useable list of variables?
And how do I then make that list appear in my jinja2 template in an option
dropdown. I guess I need a function but I am a green programmer.
> 
> Would so appreciate help.
> 

You can make a list like so:

emails = [db[user]['email'] for user in db]

Or depending on if the couchdb lib mimics a dict:

emails = [user['email'] for user in db.itervalues()]

This syntax is documented in the tutorial:
http://docs.python.org/tutorial/datastructures.html#list-comprehensions

But you can do a for loop in Jinja anyway, something like:

<ul>
{% for user in db %}
  <li>{{ db[user].email }}</li>
{% endfor %}
</ul>

Also you might want to have a look at one of the Flask extensions for
CouchDB:

* http://packages.python.org/Flask-CouchDB/ ("approved" by the Flask
developer)
* http://packages.python.org/Flask-CouchDBKit/

Jinja is documented here: http://jinja.pocoo.org/

Hi Alasdair,

I think we need a bit more context. What does your view look like ?

On 19 October 2010 17:21, Alasdair Macmillan <al@atomised.coop> wrote:
> I am a real beginner programmer and I am trying to do something in 
Python but I'm stuck. I have a list of users in Couchdb (using python 
couchdb library & Flask framework) who have a username (which is the _id) 
and email. I want to use the list of email addresses in a select box in a 
jinja2 template.
>
> My first problem is how to access the email addresses. If I do:
>
>    for user in db:
>        doc = db[user]
>        emails = doc['email']
>        print options
>
> I get:
>
>    email@domain.com
>    otheremail@otherdomain.com
>    yetanotheremail@yetanotherdomain.com
>
>
> So I can get my list of emails. But where my brutal inexperience is 
showing up is that I don't know how to then use them. The list only exists
in the for loop. How do I return that list as a useable list of variables?
And how do I then make that list appear in my jinja2 template in an option
dropdown. I guess I need a function but I am a green programmer.
>
> Would so appreciate help.
>
>