[web2py] Re: field value from row in a view
On Sunday, August 2, 2015 at 9:18:11 AM UTC-7, P Page-McCaw wrote:
I am having a hard time understanding how to get values from a row in a
view. I think I am being really dim. (It would really help us amateurs to
have a more full description of how to do database queries. Really I need
The Very Stupid Person's Guide to... because I read the guide and then do
what it says (or so I think) and can't get it to work.
The generic problem is how to retrieve data from a linked table in a view.
I have problems (this tells you how pathetic I am [really though I'm a good
biologist]) both where I want to traverse from the table that carries the
'reference other_table' field and from the target table. I keep thinking I
get the syntax, but the next time I try, fail.
I have tried many things and though I can get the entire row to show up on
the web page with many variants of:
{{ =db.table_1_name(m.field_name) }}
This shows in the page as Row {'other_table_field_name', 'value'} with
the whole row rendered as text. So clearly the row is accessed in the view.
But what I want is table_1_name.'other_table_field_name' and
{{ =db.table_1_name(m.field_name).field_name }}
returns an error: can't get field_name from None Type and m.field_name
yields the id for the correct reference to the table_1_name. m is the row
of the set being iterated through.
Somewhere, something is being gently and kindly coerced. But I am not
smart enough to figure out what is happening.
Thanks
While we're waiting for some more details, as Anthony and Jorge requested,
note that a query typically returns a Rows objects, which is a collection
of Row objects (essentially a list() of Row objects.
It just occurred to me that the way you wrote your questions makes it look
like you're trying to do queries in the view. It is much more natural to
do queries in a controller, and my example fits with doing things that way.
[1]
You'd do something like this to print the second (0 +1) and fifth Row in a
Rows object:
results = db(table_1_name().select(table_1_name.field_name)
print results[1]
print results[4]
Now we only selected 1 column in this example, but a Row object is
essentially a Python dictionary, so if we had
multiple fields,
results = db(table_1_name().select(table_1_name.field1_name,
table_1_name.field2_name)
print results[1][field1_name]
would use the string field1_name as the key, and print the value of
field1 in the second Row object returned.
This should look familiar if you've been reading
URL:http://web2py.com/books/default/chapter/29/06/the-database-abstraction-layer#select
The methods .first() and .last() can pick up the first Row object and
last Row object without your knowing how many Row objects there are; nice
convenience tools.
[1] You can also do things in the web2py shell ('python web2py.py -S
appname', but you need to invoke your model declarations explicitly (I did
cut-and-paste of the 'db = ' line of db.py, and then the 'db.define _table'
line of the particular table I was using for checking my answers.
Welcome aboard the web2py cruise; I hope this helps.
Dave
/dps
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[web2py] Re: field value from row in a view
I think we need to see actual code, including the model definitions and the
query in the controller, as well as the actual error reported (the NoneType
error doesn't quite make sense if the previous example did really return a
Row).
On Sunday, August 2, 2015 at 12:18:11 PM UTC-4, P Page-McCaw wrote:
I am having a hard time understanding how to get values from a row in a
view. I think I am being really dim. (It would really help us amateurs to
have a more full description of how to do database queries. Really I need
The Very Stupid Person's Guide to... because I read the guide and then do
what it says (or so I think) and can't get it to work.
The generic problem is how to retrieve data from a linked table in a view.
I have problems (this tells you how pathetic I am [really though I'm a good
biologist]) both where I want to traverse from the table that carries the
'reference other_table' field and from the target table. I keep thinking I
get the syntax, but the next time I try, fail.
I have tried many things and though I can get the entire row to show up on
the web page with many variants of:
{{ =db.table_1_name(m.field_name) }}
This shows in the page as Row {'other_table_field_name', 'value'} with
the whole row rendered as text. So clearly the row is accessed in the view.
But what I want is table_1_name.'other_table_field_name' and
{{ =db.table_1_name(m.field_name).field_name }}
returns an error: can't get field_name from None Type and m.field_name
yields the id for the correct reference to the table_1_name. m is the row
of the set being iterated through.
Somewhere, something is being gently and kindly coerced. But I am not
smart enough to figure out what is happening.
Thanks
--
Resources:
- http://web2py.com
- http://web2py.com/book (Documentation)
- http://github.com/web2py/web2py (Source code)
- https://code.google.com/p/web2py/issues/list (Report Issues)
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[web2py] Re: field value from row in a view
can you show us your controller? and db model?
On Sunday, August 2, 2015 at 11:18:11 AM UTC-5, P Page-McCaw wrote:
I am having a hard time understanding how to get values from a row in a
view. I think I am being really dim. (It would really help us amateurs to
have a more full description of how to do database queries. Really I need
The Very Stupid Person's Guide to... because I read the guide and then do
what it says (or so I think) and can't get it to work.
The generic problem is how to retrieve data from a linked table in a view.
I have problems (this tells you how pathetic I am [really though I'm a good
biologist]) both where I want to traverse from the table that carries the
'reference other_table' field and from the target table. I keep thinking I
get the syntax, but the next time I try, fail.
I have tried many things and though I can get the entire row to show up on
the web page with many variants of:
{{ =db.table_1_name(m.field_name) }}
This shows in the page as Row {'other_table_field_name', 'value'} with
the whole row rendered as text. So clearly the row is accessed in the view.
But what I want is table_1_name.'other_table_field_name' and
{{ =db.table_1_name(m.field_name).field_name }}
returns an error: can't get field_name from None Type and m.field_name
yields the id for the correct reference to the table_1_name. m is the row
of the set being iterated through.
Somewhere, something is being gently and kindly coerced. But I am not
smart enough to figure out what is happening.
Thanks
--
Resources:
- http://web2py.com
- http://web2py.com/book (Documentation)
- http://github.com/web2py/web2py (Source code)
- https://code.google.com/p/web2py/issues/list (Report Issues)
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