I just set up the environment for an existing Django project, on a new Mac. I know for certain there is nothing wrong with the code itself (just cloned the repo), but for some reason, Django can't seem to retrieve data from the database.
I know the correct tables and data is in the db.
I know the codebase is as it should be.
I can make queries using the Django shell.
Django doesn't throw any errors despite the data missing on the web page.
I realize that it's hard to debug this without further information, but I would really appreciate a finger pointing me to the right direction. I can't seem to find any useful logs.
EDIT:
I just realized the problem lies elsewhere. Unfortunately I can't delete this post with the bounty still open.
Without seeing any code, I can only suggest some general advice that might help you debug your problem. Please add a link to your repository if you can or some snippets of your database settings, the view which includes the database queries etc...
Debugging the view
The first thing I would recommend is using the python debugger inside the view which queries the database. If you've not used pdb before, it's a life saver which allows you to set breakpoints in your Python script and then interactively execute code inside the interpreter
>>> import pdb
>>> pdb.set_trace()
>>> # look at the results of your queries
If you are using the Django ORM, the QuerySet returned from the query should have all the data you expect.
If it doesn't then you need to look into your database configuration in settings.py.
If it does, then you must might not be returning that object to the template? Unlikely as you said the code was the same, but double check the objects you pass with your HttpResponse object.
Debugging the database settings
If you can query the database using the project settings inside settings.py from the django shell it sounds unlikley that there is a problem with this - but like everything double check.
You said that you've set up a new project on a mac. What is on a different operating system before? Maybe there is a problem with the paths now - to make your project platform independent remember to use the os.path.join() method when working with file paths.
And what about the username and password details....
Debugging the template
Maybe your template is referencing the wrong object variable name or object attribute.You mentioned that
Django doesn't throw any errors despite the data missing on the web
page.
This doesn't really tell us much - to quote the Django docs -
If you use a variable that doesn’t exist, the template system will
insert the value of the TEMPLATE_STRING_IF_INVALID setting, which is
set to '' (the empty string) by default.
So to check all the variables available to your template, you could use the debug template tag
{{ debug }}
Probably even better though is to use the django-debugging-toolbar - this will also let you examine the SQL queries your view is making.
Missing Modules
I would expect this to raise an exception if this were the problem, but have you checked that you have the psycopg module on your new machine?
Related
My django app uses update_or_create() to update a bunch of records. In some cases, updates are really few within a ton of records, and it would be nice to know what got updated within those records. Is it possible to know what got updated (i.e fields whose values got changed)? If not, does any one has ideas of workarounds to achieve that?
This will be invoked from the shell, so ideally it would be nice to be prompted for confirmation just before a value is being changed within update_or_create(), but if not that, knowing what got changed will also help.
Update (more context): Thought I'd give more context here. The data in this Django app gets updated through various means (through users coming on the web site, through the admin page, through scripts (run from the shell) that populate data from a csv etc.). The above question is important mostly for the shell scripts that update data from csvs, hence a solution at the database/trigger/signal level may not be helpful here (I guess).
This is what I ended up doing:
for row in reader:
school_obj0, created = Org.objects.get_or_create(school_id = row[0])
if (school_obj0.name != row[1]):
print (school_obj0.name, '==>', row[1])
confirmation = input('proceed? [y/n]: ')
if (confirmation == 'y'):
school_obj1, created = Org.objects.update_or_create(
school_id = row[0], defaults={"name": row[1],})
Happy to know about improvements to this approach (please see the update in the question with more context)
This will be invoked from the shell, so ideally it would be nice to be
prompted for confirmation just before a value is being changed
Unfortunately, databases don't work like that. It's the responsibility of applications to provide this functionality. And django isn't an application. You can however use django to write an application that provides this functionality.
As for finding out whether an object was updated or created, that's what the return value gives you. A tuple where the second value is a flag for update or create
I have tried many, many times to get my apps running on Heroku without success. The fact that they run locally seems to be totally irrelevant. Clearly I don’t understand how this works.
So … here are a couple of questions, which I've decided to group to gether in a single question on SO:
1. Why does Heroku have so many different places that influence the settings (Procfile, wsgi.py, config vars, and settings.py)?
2. How do they relate to one another?
3. Which has precedence?
4. Do they all have to be exactly the same?
5. What am I supposed to do with / how am I supposed to configure the database settings given in the Heroku Django template?
# Parse database configuration from $DATABASE_URL
DATABASES['default'] = dj_database_url.config()
# this line blank in original. I put text here to make it format correctly
# Enable Connection Pooling (if desired)
DATABASES['default']['ENGINE'] = 'django_postgrespool'
a) Doesn’t DATABASE [‘ENGINE’], coming after DATABASE [default] overwrite DATABASE [default]?
b) Why aren’t these two in the same format as the default Django settings, which is a simple dictionary, instead of all these extra and confusing brackets?
c) Are they supposed to be treated as two different settings, so that you have to use database routers if you want both?
d) Why does the devcenter article say to import postgrespool but the template says nothing about that?
e) Why is ‘default’ optional with dj_database_url but mandatory with Django?
f) When I tried commenting out line 82, I got an error about resetting queries, why?
g) I have the postgres string from my config vars as the argument to dj_database_url, but I get a NAME ERROR, database undefined. Why?
You're making this much much much more difficult than it actually is. All dj_database_url does is use an environment variable to create a dictionary suitable for use in the DATABASES setting. It doesn't do anything else.
The devcenter article you link to mentions processpool as a way of increasing concurrency. It doesn't say or even hint that you need it when you're starting out. There is no reason for you to even be reading that article at this point.
The only article you need to read is the Getting started with Django one, which tells you exactly what to do.
In my Django app, I'm getting a 404 Page Not Found response that looks like it's being caused by some logic in one of my custom template tags -- but I don't know which one.
Using Django Debug Toolbar's Request Vars panel, I can see the view causing the 404 is go_back.utils._register_wrapped_view -- which is how I know it's coming from one of my go_back.utils template tags.
Unfortunately, because template tags need to be decorated and thus show up as _registered_wrapped_view, I can't tell which tag it is, much less where in the tag code the problem happens. (The tag code is a special utility which works with urls and calls resolve in several places so it's not obvious.)
Thus I can't use the normal import pdb; pdb.set_trace() approach because I don't know where to set the trace.
So how can I get pdb to break when the 404 happens so I can see the stack trace leading to that point?
Try using the Django Debug Toolbar, it can intercept redirects, good for when you cant find where to add a breakpoint.
In settings make sure you have
DEBUG_TOOLBAR_CONFIG = {'INTERCEPT_REDIRECTS': True}
Old question, but there is django-pdb which has a post mortem flag for runserver. It doesn't look well maintained (2 years ago is the last commit), but it is simple middleware and updating it shouldn't be too hard.
I'm not sure if you know this:
You can try putting import pdb; pdb.set_trace() in the function which you want to debug and development server. When that function triggers it will break into pdb shell and you can debug your code.
So I'm working on a website where there are a couple important values that get used in various places throughout the site. For example, certain important dates, like the start and end dates for registration.
One way I can do this is making a model that stores these values, but that sounds like overkill (since I'd only have one instance). Another way is to store these values in the settings.py file, but if I wanted to change them, it seems like I would need to restart the webserver for them to take effect. I was wondering what would be the best practice in Django to handle this kind of stuff.
You can store them in settings.py. While there is nothing wrong with this (you can even organize your settings into multiple different files, if you have to many custom settings), you're right that you cannot change these at runtime.
We were solving the same problem where I work and came up with a simple app called django-constance (you can get it from github at https://github.com/comoga/django-constance). What this lets is store your settings in a settings.py, but once you need to turn them into settings configurable at runtime, you can switch to a Redis data store with django admin frontend. You can even use the value from settings as your default. I suggest you try this app out.
The changes to your code are pretty minimal, as pasted from docs you initialize your dynamic settings like this:
CONSTANCE_CONFIG = {
'MY_SETTINGS_KEY': (42, 'the answer to everything'),
}
And then instead of importing settings from django conf, you do this:
from constance import config
if config.MY_SETTINGS_KEY == 42:
answer_the_question()
If you want a specific set of variables available to all of your template, what you are looking for is Context Processors.
http://docs.djangoproject.com/en/dev/ref/templates/api/#writing-your-own-context-processors
More links
http://www.b-list.org/weblog/2006/jun/14/django-tips-template-context-processors/
http://blog.madpython.com/2010/04/07/django-context-processors-best-practice/
The code for your context processors, can live anywhere in your project. You just have to add it to your settings.py under:
TEMPLATE_CONTEXT_PROCESSORS =
You could keep the define your constants in your settings.py or even under a constants.py and just
from constants import *
However as you mentioned, you would need to reload your server each time the settings are updated. I think you first need to figure out how often will you be changing these settings? Is it worth the extra effort to be able to reload the settings automatically?
If you wanted to automatically enable the settings, each time they are updated you could do the following:
Store settings in the DB
Upon save/change, write output to a file
settings.py / constants.py reads files
reload server
In addition, you have a look at the mezzanine project which allows you to update settings from the django admin interface and will reload as well.
See: http://mezzanine.jupo.org/docs/configuration.html
If the variables you need will be updated infrequently, i suggest just store them in settings.py and add a custom context processor.
If you are using source control such as GIT, updating will be quite easy, you can just update the file and push to your server. For really simple reloading of the server you could also create a post-recieve hook for git that will automatically reload the server when new code is pushed.
I would only suggest the other option if you are updating settings fairly regularly.
I have a Django app that runs a tool and displays the results from the tool back to the user using a Django template. Sometimes Django does not display the results. It doesn't complain about anything, it just doesn't display the results. I'm guessing this is something to do with one or more of the characters in the results being illegal as far as Django is concerned. How can I get more information about what it is that Django doesn't like? Also, is there some method I can use to filter out "bad" characters? The results are normally just lots of text. They contain company confidential stuff, so I can't give an example unfortunately. I have DEBUG set to True and TEMPLATE_DEBUG set to DEBUG.
UPDATE:
I added some code to filter out all chars with a decimal value greater than 127 and it now works.
If you are using the development server, put in a breakpoint with pdb and see what is going on. Or print out the string that you think has "bad" characters. If you aren't using the development server you could use the Python logging module to log the string you are getting from the tool.
You might be leaping to conclusions about the data containing bad characters. It may be something else, and without debugging further it is hard to speculate.
you could try using the built in django encoding methods to remove illegal characters.
from django.utils.encoding import smart_str
smart_str(your_string)