Heads up! To view this whole video, sign in with your Courses Plus account or enroll in your free 7-day trial. Sign In Enroll
Preview
Start a free Courses trial
to watch this video
There's an amazingly handy plugin for Django that helps us spot dangerous queries and other problems. Let's take a look at `django-debug-toolbar`.
Sending emails? This panel gives you a preview of your emails right in the Django debug toolbar.
If you want the documentation for django-debug-toolbar, it's right here.
Remember, you don't need the SHOW_PANEL_CALLBACK setting when you're using django-debug-toolbar locally or on a live server. I did that only because I'm using Workspaces.
Quite often,
when you're building a Django site,
0:00
you need a sanity check on
various bits and pieces.
0:02
Did that template actually get used?
0:05
How many queries did I run?
0:06
How long did all those queries take?
0:08
You could of course track all of
these things down in the code and
0:10
log them out to a file of the terminal.
0:12
Raise your hand if you wanna do that?
0:15
Yeah, I don't either.
0:16
Thanks to Rob Hudson and many o we
don't have to do all of that work.
0:18
Their project, Django Debug Toolbar,
came out several years ago and
0:22
quickly became an indispensable part
of many Django developers workflow.
0:25
Django Debug Toolbar provides us with
a huge amount of valuable information
0:29
as we're building and yes,
debugging our software.
0:33
Let's look at how to install and use it.
0:36
Installing Django Debug Toolbar is
actually just remarkably simple.
0:39
It used to be a bit more involved and if
you're working on an older Django project,
0:43
you might see more settings
related to the toolbar.
0:46
In fact, we have to do a special thing
now just because we're on workspaces but
0:49
I'll walk you through that in a minute.
0:53
We're gonna to start by installing
the debug toolbar with pip.
0:55
So pip install django-debug-toolbar.
0:59
And I actually know that for running
things in a new workspace, you don't see
1:04
this but I fork workspaces a whole lot
when I'm creating these courses for you.
1:08
I need to install markdown too, so
I'm gonna go ahead and do that.
1:12
All right, so
we have two are installed and
1:17
now we need to go to our settings file.
1:21
Settings.pi and we're gonna come
down here and in installed apps,
1:24
after static files,
we're going to add debug toolbar.
1:30
And you can put it after
courses if you want,
1:37
but I like to always have my
own custom things that I built
1:39
listed last just because that way,
I'm kinda know where things are.
1:43
You have to come in after static
files though because Django the debug
1:48
toolbar needs some static files.
1:51
So here's the thing that's special
that we have to add ourselves.
1:53
So, let me explain a bit
of how this works.
1:57
Django debug toolbar expects that
all the requests coming to your app,
1:59
it checks to make sure that
the setting debug is set to true and
2:04
it also checks to make sure that
you're coming from your localhost.
2:08
So from 127.0.0.1.
2:12
So, we can do this setting
in two different ways.
2:15
First thing is we have to
add in debug toolbar config.
2:20
And this is a dictionary.
2:25
So we have two settings that we can set,
2:27
one of these is show toolbar callback and
the other is internal IPs.
2:29
Internal IPs is a little bit easier.
2:33
We can just do internal_IPs, and
then this is set to a list of IPs.
2:35
So the one that we want to set it to
is we'd want to have say, 127.01.01.1.
2:42
And maybe we don't wanna have ::1 for
the IP6.
2:50
And then we can just do all zeroes and
2:53
everything's considered an internal IP,
I do believe.
2:58
But, this is a little bit messy and
it's a little weird.
3:02
So, instead of doing that one,
3:06
I'm actually going to do something
that's arguably even more messy.
3:07
But, it's explicitly like weird so
I'll remember to take it out.
3:11
So I'm gonna make a new key here
that is SHOW_TOOLBAR_CALLBACK.
3:16
And so this is a function to
be run to determine whether or
3:21
not to show the toolbar.
3:24
So this gonna be an actual
function that you write or
3:25
this can be a dotted path to
a function somewhere else.
3:27
I'm just gonna write a lambda and
it's gonna get an argument.
3:31
I don't even care what the argument is,
I just wanna return true.
3:33
All right, so,
we added it to installed apps and
3:37
then simply because we're on work spaces,
we added this.
3:41
You will not need these last three lines.
3:44
If you're working on your local machine,
leave those out.
3:47
You don't need these at all.
3:50
And you don't want to put
these on to a remote server.
3:51
All right, so we've saved that and
now let's go run our server.
3:55
Oops, sorry I got to
get into learning site.
4:05
And there we go.
4:11
And then we can preview
our site on port 8000 and
4:12
look, here's our debug toolbar,
isn't that cool?
4:16
So, this is our toolbar and one of
the things that you know right away,
4:20
is that you can hide it by
clicking this hide button.
4:23
And now you have this
little tab that sticks out,
4:26
you can click that to bring
out the toolbar again.
4:28
Django Debug Toolbar is really smart.
4:31
It will remember whether or
not you wanted hidden.
4:32
And if you said to hide it, then it won't
show up on page except there's a little
4:36
button and if you leave it open,
then it'll be open all the pages.
4:39
So, let's look at what's
below the hide button.
4:42
There's a lot of stuff here.
4:45
So this version's tab tells us the version
of things that we are running.
4:46
So we have 1.4 the toolbar,
1.9 of Django and 3.5.0 of Python.
4:51
So that's cool.
4:56
The time tab tells us how long the page
the pager whee're on took to render and
4:58
this is both in Python and in the browser.
5:02
So this is kinda cool.
5:06
You can kind of see like
what's taken the most time,
5:07
look we're spending a whole
lot of time in the CPU.
5:09
Maybe we can get rid
of that kind of stuff.
5:12
Settings, it just shows
you all of your settings.
5:15
There's a lot of settings.
5:18
Headers shows you the HTTP headers and
5:20
the WSGI environ settings for
your current page, your current view.
5:23
Request, that's our next one and this
shows us information about the request.
5:31
This is what view we're in,
we're in the hello world view.
5:34
There were no arguments, there were no
keyword arguments, and a URL name is home.
5:37
So this is really handy for debugging
like how did I get the view that I'm in?
5:41
SQL shows us how many queries were
run on the page that we're on.
5:47
So currently there was one query and
it took 19 and a half milliseconds.
5:50
So that's cool.
5:54
And this cell, that shows you like
what was actually run and everything.
5:55
And then the expel, E-X-P-L,
6:01
will show you the explanation of
the query if your engine supports it.
6:03
So pretty handy.
6:09
We're gonna be using this panel a lot.
6:10
So just kinda get used to it.
6:11
Static files shows you all the static
files that were loaded for
6:14
the particular page that you're on.
6:17
What's cool though,
6:20
is it shows you the apps that have
static files that are being loaded.
6:21
And then also like, everywhere that's
being looked at for static files and
6:25
all that stuff.
6:29
So this can be really really handy for
debug.
6:30
Templates works very similarly.
6:33
These are the templates that were loaded.
6:35
So you can see that we loaded home.html,
6:37
we loaded layout.html, and
we loaded coursenav.html.
6:39
And we also get the context
processors that handle
6:44
putting things into the template.
6:46
If we had a cache,
then the cache stuff would show up.
6:49
Signals run depending on what's
happening in your Django app.
6:53
So like when you save a model,
there is a pre-save and
6:57
post save signals that are fired off.
7:01
So the show you which signals are like
7:05
involved in the requests
that we're currently on.
7:08
We'll, do more of these in a workshop or
something later on.
7:10
And the last panel is this logging panel
and if we were sending any messages out to
7:14
the logging system that Django go has,
they would show up here.
7:18
Pretty handy to be able to see like I
logged that but I can still look at it.
7:22
The last thing on the panel is this thing
down here that has intercept redirects,
7:25
if you check this box.
7:31
And then you go to a view
that would do a redirect.
7:33
So like you submit a form the form, hits
the view the view is like yeah everything
7:35
is good and
does a redirect to another page.
7:39
Checking that box would
stop that redirect.
7:42
This is really handy, if you want to
be able to see in the debug toolbar
7:45
what happens after your submit a post.
7:49
Most the time I leave this off until I
need it because it's one of those thingsll
7:52
just get in your way.
7:55
And the checkmarks also
let you turn off panels.
7:57
If you don't gonna be using them like if
we don't care about the settings panel.
7:59
Then we can turn off the settings panel.
8:03
Sometimes that's handy sometimes
it's not leave it up for you.
8:05
The debug panel will help us a lot with
our Django development and fine tuning.
8:08
You should go do a search on pipe API for
debug panel and
8:13
see just how many packages are out there
to add new panels to the Django debug tool
8:15
bar I'll put a link to the toolbars
documentation in the teachers note too
8:19
You need to sign up for Treehouse in order to download course files.
Sign up