WEBVTT

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let's start talking now about the Python
Standard Library now this standard

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library that ships with Python
provides a wide range of modules that we

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can use so it includes everything built
into the language that we can use

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without explicitly importing anything
plus whole lot of other useful modules

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such as shelve and random which of course
we've used in the course previously now

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I did say without explicitly importing
anything because the core built in modules

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are imported for us automatically
so I'm gonna create a new file this is the

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same project from the previous video so I'm gonna create a new Python

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file and will call this one example so when
useful command that's gonna let us see

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is dir command or dir function and thoes that uses will note that this is not

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related to the dir command you can use
from a command prompt to print out a

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list of directories so to see what is
imported for us automatically we can

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print the output from dir so we could do
something like....

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to call the dir method run that and right

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click Tim and click run example I remember this time
and you can see when I've done that

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we got a whole heap of information

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as you can see there, now we're gonna be
covering this in a lot more detail later

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but it's worth noting that anything
whose name starts with an underscore

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here is something that we shouldn't be
changing without good reason so if the

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name starts with two underscores like
these two and then not intend to be

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changed at all so in fact
there's no such thing as private

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variables in Python and everything is
available everywhere but the convention

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is to use underscores to intention so starting a name

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with an underscore indicates that it's
private to its module but it's up to you

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as the programmer to inspect that convention
because Python itself doesn't prevent you

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from changing and that's done by design

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but getting back to the dir as you can see on the screen
here now we are not going to look at most of the entries as they are

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to do with the internal running
of Python but a good one here is this

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first one underscore underscore builtins
underscore underscore this is the module containing

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the Python built-in identifiers and there is
actually a list that I'm going to put on the

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screen and I'll share this link in the
Resources section and will just open a

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browser and go that URL now that's a decent list of all
the built-in functions from or based on

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that module the built-in
modules but with that said that's one way of

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doing it but we can
also use the command to find out a bit more as well

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so come here on the next line ill put..

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...and if we run that that gives us a whole heap of

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stuff and obviously you want to scroll that
but this is Python so we can easily

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display that of course in a more readable
format as we've done this before so

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let's just comment that line out and use our

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handy for so.....so run again and I need a colon there so run again and now we got a decent list here so we got

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a whole heap of errors at the top but also just scrolling
down the list you will see there is the false one

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there is none we seen that before and true down here as well that just 3 and....

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if you go a bit further you can see the dir hex input

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and bin up here

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slice and so on so essentially you should be able to
recognize quite a few of these other

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entries and even things like list is
there on the screen

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map open print etc of course that's more
interesting than actually useful but if

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we import shelve we can have a look at
what that provide so lets close this down

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so just delete the codes here and start again so
what we can do is import shelve and

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have a look at what it actually provides so...

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....and run that and you can see
we got a whole heap of bits and pieces there

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relating to shelve and the first list
shows you shelve on the list because we imported

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it that's now coming up in our list when
we print dir and printing dir on the shelve as you see on the

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third line there has shown the objects and
methods available from the shelve module

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of course we've used the open function
before to open a shelve and this returns

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a shelve object so you may notice that
close doesn't appear in the list and I'll just run it again

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so looking at the list when we use open there is the
open method in the end and when we do

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that it returns a shelve object one of these
but you will notice that close doesn't

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appear in the list and that's because
it's a method of the shelve

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class we're not interested in the
underscore method so we can filter out to see what

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a shelve object provides just to show you how that works so we can do something like, will leave the shelve import there and will put...

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and I will put a test here to ignore underscore so..so let us run that and you can see now

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that apart from pop and popitem we've
seen all these other methods either when

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looking at shelve or when discussing
dictionaries and in face Intellij provides

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a similar list plus a lot more in order
of completion we type the full stuff after shelve

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so if we type something here going back
to the code so if we type....you can see there is

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a big list of things that IntelliJ
will bring up automatically

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IntelliJ is quite smart that way that it
can present all this information to us as well

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now some of the standard modules are
written in C these are generally the

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ones that provide access to system
functionality such as File I/O but many of

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them are actually written in Python
and we can examine the source code from

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IntelliJ holding down the Ctrl
key and clicking on the module name shelve

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in this case so we can come over here
and we can I believe its control

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on a PC but on a MAC it is command click on
a command hold command down and click on

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shelve that's gonna give us access to the
source code for the shelve.py and

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you can just scrolling down there is some actual code
that is part and parcel of Python

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so until we have covered functions and classes the code you can see on the screen

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probably looks a bit horrible to you so we are gonna leave it there and have a look at some of the

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standards library code later in the course
so on the next few videos we are gonna look at

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some of the modules that come with Python but
will finish this video by saying how the

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help function can be useful to work out how to use some of the

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various modules

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so let us just close this file off we only got shelve imported so what I'm gonna do is delete that and on

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line 3 I'm gonna type....

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if I run that you can see that actually
gives us quite a bit of information

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about , quite a detailed amount of
information about shelve how to use it

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description of what it is the various
parameters interfaces and so on and also a link to the

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documentation

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so you can see here there is a link we can get and from
their we can click on that goes straight

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to documentation in a browser so copy that
go back to the browser and press enter

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generally following the link is better
because you get the object or output rather

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you got this way of looking at the data or coming
back to a browser and seeing it in that format

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to me I would prefer to use this format the
browser I think it's a lot easier to

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read but it's personal preference and
you got the ability to choose either way

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when you actually choosing a
documentation and we do suggest that you

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do take some time in read this
documentation you don't need to know

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or understand it word for word but it can
be a good way to help solidify your

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understanding of how some of the
internals work within Python it is really really

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handy and you can also request help on
individual functions so for

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example we could change that to import
random and here we could type...

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.....and we can get some help just on that again it is quite
short but it does give you the

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information relating to the parameters and so forth for that particular function

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so I'm gonna end this video here in the next one
we're going to continue our discussions

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of modules and imports