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