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one of the simplest modules in the
Python standard libraries is web browser

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which doesn't actually implement a web browser
despite the name but what it does it is allows

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you to launch one of your installed
browsers and navigate to a particular url

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so this example is going to do just
we are going to launch using your

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computers default browser the system's
default browser and navigate to

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the python home page so type....
to

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import that library and type... and
type in the URL so....

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and if I right click that and click on run and by the way I've
created a new project called web

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browser and a new Python file called browser.py
so I run browser you can see

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it automatically open the browser and the
and the browser opens up Python.org

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so you saw previously how the help function can
display a url giving more help on a

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module or a function so help itself has
actually as it turns out user's Web

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browser to perform that
functionality

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because this is such a simple module
provides what we think is a

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good example for looking at the
documentation and

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learning how to read it so we're not
gonna cover every single module on the

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standard library but by the time you
finish this section we should be able to

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work out how to use any other modules
that we don't specifically cover by sort

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of referring to the documentation so
gonna go to the documentation for web

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browser explaining how it is set out and
what are the various terms in the

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documentation actually mean now the aim
here again is to provide you with the

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knowledge you need to use a
documentation for any other modules so

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whether that part of the standard library or for
that matter additional modules that you

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may install on your computer and as part
of you will get a general idea of the style and the

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level of detail required for useful
documentation and that will help when it

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when the time comes to document your own
functions and

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modules which is another important aspect
of programming let's go ahead and

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just make a modification to our
program we got our web browser opened so what we gonna do

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is add another line now we are going to type....
and put web browser in brackets like so

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we're gonna run it which will open the
browser and that's navigating you

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can see its open another tab in the browser
and that's worked find but if we now tab

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back to our program on the
right hand side we actually got some

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documentation showing up and that's
what's come up as a result of calling

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helped or putting the code line 5 help web browser being name of the standard

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library module so getting help web
browser itself provides a link to this

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link and I'm going to click on that and copy it rather
and go back to our browser so we can see it in

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there its actually going to their you can see the link
is...

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....and that can
be slightly different to using a

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different version of Python but
let us go through that page anyway and explain any

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details that we haven't explained before
that you may not come across before

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incidentally if we go back to our code there is the
link that I was talking and this

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one is actually 3.5 the other one is 3.4 but it does depend
on the version and you got a good overview of

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what this module is all about

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obviously interfaces for launching
remotely controlling web browser and

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its got the various functions and so on so
go back to the browser and you can see

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it's telling us their that it provides a high-level
interface to allow displaying a web

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based documents to users and most
circumstances simply calling the open

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function which already done from this
module will do the right thing and you

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can see that in our case it successfully
worked and when I use the term

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high level interface what it is saying is no
need to understand such things as

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transport protocols or networking really
your just calling open and everything else

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happens magically so that's really
what it is saying in there now this is a

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standard way of displaying documentation
for the various modules in Python

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and the descriptions generally within
going to describe any special situations

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that you should be aware of in other
words any behavior that may vary from

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one operating system to the next and also
some usage instructions if the module

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can be called in various ways and you can see on
the screen for the web browser module will

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warned that the program will block on
UNIX systems if a graphical browser is not

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available so that might seem odd but at
one time all browsers were texts base and

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I remember myself being introduced to the
internet in 1992 and I

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was using a text based browser
and even npw there is still some text base browsers

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on linux platforms primarily linux such as links
in which is use fairly heavily

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the other thing to note is that some browsers
for people with vision impairment

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count as text mode browsers so when it
says the calling process will block the

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documentation means that the program
will not continue until the text mode

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browser has been closed

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obviously in the case of this
application when we ran it , it open the browser for

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us automatically but it didn't stop the program
so the program continued on and created

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that helped to the right hand side of
code, created this automatically in another words

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executed the next line so it didn't
block in other ways in other words so

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this documentation in the screen here is
basically to textual representation of

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that graphical documentation from
that's in the chrome browser and you can

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see it automatically because I'm running
a Mac it loaded that that was my default

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browser chrome and that's why use that to
open the url that we gave on line 3

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so if a graphical browser is available or the
program's not running under UNIX the program will continue

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once the browser has been launched and we saw
that work there if the program had been block though

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we wouldn't see the results of calling
help until we close the browser and

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clearly the browsers still running when we got it to
work so it's quite important to

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understand that and that's the sort of
thing that's generally mentioned

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documentation to give you some gotchas
to know that under certain circumstances

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specific things may happen and we are gonna
cover this when we look at creating our

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own modules but it is possible to create
a .py file that can be executed as a

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script and also imported into other
modules now web browser itself that modules

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is being written in this way so that the
documentation mentions how it can be

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executed as a script from the command
line

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you can see there its talking about how
it can be invoked from a command line

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and you notice that the line has got a
couple of extra parameters as well and you

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notice there is a couple of options on
their -m as a parameter if your calling from the command

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line opens the URL in the browser window
if possible and -t

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opens the url in a new browser page which is a
tab and obviously can only do one or the

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other you can't do both because it is only gonna be only the being new browser window or

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a tab the point of all this is that the
documentation is where you go to find this

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types of information when you're
dealing with Python modules now there is also

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talk there about exceptions as you can see
and we haven't looked at

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exceptions yet but they're a really
useful way to handle errors in programs

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the note about the exception what they
talk about their with the error that will

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make more sense later in the course once
we have been through exceptions so the rest of the

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documentation as we scroll down is describing
the various functions available in

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details of how to use them the open
function for example you could see there

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we got that at the top of the screen there is called
to provide it with the url which will

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then attempt to open a window in
which we saw and there is also other versions

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of that as well there is other parameters we
can call when we're creating that so again you

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can see how it's very useful to go
through a module and find the

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documentation for it particularly with
a standard library module that's part of

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Python to understand the various
parameters and how to use them and to

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see what's available sometimes just going
through the list the documentation

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should say for specific a module is really
handy to see different parameters and

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again we used the .open but there's
also there's this other options here ....

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.....and describing what they're
actually used for as well so we've been using

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functions a lot of course the most
common is using print which we have seen

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numerous times which just displays the
arguments provided on the screen so this is a

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probably a good time now to have a quick
look on arguments parameters in Python's

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named parameters so what we would do is to stick to the
print function to define those terms

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back to the code editor and I know you have seen
something similar to this and I'll just

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closed down this run window as well and we will close this down and comment those out for now we won't use those

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will comment out the help line as well so you've seen this before...

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and we run that....unsurprisingly the numbers from 0 through 9
but notice as I stop typing

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when I was typing now notice there its got objects but its got these other
things on the end of the list as well so

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the Asterix before objects that means
that we can provide several objects

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separated by commas and we've used this
couple of times in the course so it shows

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that we can do things like the following
we could do something like

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print.....and noting that they are all
parameters as you can see so we provided nine arguments

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and print displays them on a single line so
I won't run that but we know that it does that the values printed are

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separated by the character that is provided
for the key word argument which is the

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sep which is the second parameters which you can see there
so the default for value for sept is a

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space so we didn't specified value and
numbers were separated by spaces so let just

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run that actually so that we can see what we are talking about and that
was executed multiple times because I

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got a for loop but you can see that there's a
space between each number and that's the

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of course the default for that parameter is a space so if you
want to change that what will do is we close

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that down and at the end of the list where we
don't want to put anymore parameters we put another comma but we type....

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...for separator remember that we brought up the list before....

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....and if we run that you can see we got a semi
colon and a space between each number

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because we've set the separator is a
semicolon and a space and likewise we

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could have got rid of the space, run that and now literally the
numbers are separated only by a

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semicolon now print text three more
arguments and we have a look at those again we

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can type print...

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what we could do here is you can see the other
three parameters file and flush we've

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talked about those in section ten when we
were dealing with input output but there is also other

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option for end and that's why by default you can see its going to go to a new line /n which

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means by default after we have process the line of
output not individual pieces of

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information within a print but when it's
finished the entire print statement as to

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whether or goes to new line or not we change that to put
for example....and get rid of the second print and run that and you can see now

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that we're not going to a new line at
the end of every print is staying just

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separating it by space so this is just an example
of the print method and the various

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arguments that will actually take so let us just
go back to the web browser documentation

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documentation for the functions provided
by the web browser module it really is just showing

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the arguments the functions will accept
and then describing what they do so the

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open function requires a url which you could
see here and it can also accept two named arguments

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new and auto raise which will default to 0 when true
if not specified

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back in the code you saw the end had default value of /n in which mean the print

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will automatically go to a new line at the
of the print statement by default which if course you can override

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so lets try out some of these examples here
of using the open functions so if we go

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back to our code I'm gonna comment out that for code and actually what I'll do is just delete it to make it easier and now if we go back and

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uncomment the web browser open by
default we can you can see that would

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actually set that up to go to the url
but we can put an unnamed parameter...

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and run that

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now the thing interesting here is don't be
surprised if as in this case even though

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we used new equals 1 and we have a look at the documentation again

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new=1 a new browser window is open
if possible and new=2 a browser page

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tab is opened and in theory you think
that new=1 should open new instance of a browser so

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something like this new window that would be
completely new window but it didn't actually

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do that so the key words to remember
in this documentation is here if possible

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in this case it didn't do it opened it didn't in a
new tab and this does apply to Google

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chrome and also to Fire Fox on Ubuntu Linux for
example if you do that all three values

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result in your url being opened in a new tab of the
current browser instance as you saw in mac

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when I did that as well again the
documentation isn't incorrect it does state that

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the behaviors when apply when possible but
moving on let us look at the open_new

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this provides the same
functionality specify new=1

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and open_new_tab the next
one down provides the same providing the

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parameter the parameter new=2 and actual fact each of these functions just

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call open with the new set value or new
set sorry with new the named

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parameters set to the corresponding
value so far the web browser module has been quite

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simple you can open a URL in one of
three ways either by passing a value from

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the new parameter or calling one of the
three open functions so the urls is going to be

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opened using your operating system's
default browser and you can see in my case

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it was chrome let's look at another
function this is the get function this

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is described as returning controller object
for the specified browser type so

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hopefully you can see the table or the
defined browser types and further down the

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document we can see the available methods in a
controller on a controller is provided the three

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different ways of opening the URL that
would actually just seen using the controller as you can see their so its

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a slightly different way of accessing in
other words I just want to point out

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also that we've deliberately avoided the
register function this is a good tip when

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reading module documentation focus on the
functions that appear to do what you

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want

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only try to make sense of the other ones
if you can't find any obvious way to do

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something

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so the get function provides everything we need
to use a different browser to the system

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default so the following code if we go back to the browser I should
actually opened the url in another

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browser so if we go back to the code close this
down so comment that code out and if we change the code

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and you wanted to open in Google
chrome and I've use that as a default but on your computer you should be able

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to type....

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.....

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......

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....so if I run that I should probably get the same result
because I'm actually running chrome

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anyway that would be the code that
actually works but because I'm using a

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Mac I need to try one from another table
so go back to the documentation

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you can see Mac with the mac options I can choose Safari by typing Safari
or whatever the Mac OS X default is and just

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looking at this notes here obviously the
Mac OS X ones are only applicable for

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the Mac platform and likewise with 2 Windows
default is obviously only applicable to

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Windows platform

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so Chrome didn't work so let's just try
running chrome in our test code

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so Google Chrome and run that you can see that didn't work either so what we can also
try and do again this is probably MAC

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specific you should find these commands
I've done here should work ok on

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a Windows machine or Linux machine but
on a Mac you might have to do it slightly

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different so we can put Chrome...
instead of putting

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using we get rid of using and will just make it.....

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...lets try running again and see if that works that didn't work so I'll try actually what I did there I made a mistake

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so I need to put like so need to close of the bracket
and put .open and you can see .open is now a method within that

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function so we close it down and run it again no error this time
but we didn't see it actually open anything

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so we're on the right track here so let us try closing that down and putting Google

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Chrome run that will try .open_new_tab.....like so

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run that close that down and we will just make that chrome again I'll just try one more and again this is a Mac specific problem....

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will try and execute that and again no luck so not having much
luck with the Mac version but if we just got back

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to the documentation again what we can
do we know that we can get it to work

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using Safari so that's something that
does work on a Mac and again these

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problems are pretty much because I'm
actually running this on a Mac and you

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can see on Windows you should be able to
use Chrome or Google_chrome that

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should work just fine but it is not working on
my Mac at the moment so I'm gonna use

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Safari which we know I haven't
executed before lets go back and change

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the code for that so I'm gonna make it a lot simpler so I'm gonna go back to the code

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I have and I'm going to comment out that line for now
I'm gonna put....

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...and will put....which should now work
because we are on a Mac and that will only work on a Mac

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Chrome sorry Safari....

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...lets try that so that worked of screen so I'm going to close the tab down and

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opened it moved Safari over to
this screen and I'm just gonna make it big so we got

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2 tabs opened as you can see and if I run this
again you can see that came up and work this

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time so that's using Safari so basically the
code I was trying to work was Mac

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specific and it didn't work because we're
on a Mac but once I started putting Mac

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specific code it actually worked and again
getting back to the other code if

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you're using these codes on a Windows
machine not Mac OS X and safari but the

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other ones you should find that there's
no problems basically problem initially

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with those errors was as far as Mac was concerned
it couldn't find Google Chrome and it needs to

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be in the system path and it raise an error
and you saw those exceptions coming up

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on the screen and you'll be learning how
to deal with those exceptions later in the

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course and doing so will provide a way
to check gracefully whether a

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particular browser is available so you can
try another one if not so again you might want to

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as an exercise just try one of these
options on your computer and see if it

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actually works and you can see I actually use safari in my case and just finishing off

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I know this is getting quite long but the register
function that we skipped over getting back to the

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documentation register here that can be
used to make additional browsers

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available when Python doesn't list them in the table so in actual fact it can be

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used to make unknown browsers available in the system path and that was

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obviously the case here with those errors I was getting however with this bit of the documentation is fairly weak it doesn't

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specifically say what the constructor argument is although we could guess
what it does some sort of function there is no

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indication of what it should do the final paragraph
of register does say that the function is

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only useful if you plan to either set the
browse variable or declaring your own handler

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but again what is handler does and what form it should take is unspecified
so if you do get to the point where you feel you need

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to use a function or method that's
poorly documented your only real choices

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are to searched the internet or examine
the module source code we don't actually

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use this function right

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now which is fortunate because an
internet search in this particular

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function throws up far less information
than is normally available when it's a

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bit too soon and of course for examining
the web browser source code so hopefully this tour

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of the library documentations has given you
like a solid idea of how to use it

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and how to work out what various functions
do and how they used occasionally you'll

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find the odd bit of documentation that's not
as good as it should be as in the register

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example here on the screen but generally
speaking the Python documentation is

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quite good so we are gonna finish this lecture now with 2 last comments that be useful when

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looking at documentation and method
descriptions the first is the difference

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between arguments and parameters and
why it doesn't matter so strictly

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speaking when you write your own
function what you doing is your defining

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the parameters that its going to use and
when the function is called these

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parameters are replaced with the actual
arguments in practice most programmers

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now used to the two words interchangeably
and generally favor the word parameter

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over arguments and the Python documentation
does have a glossary entry explaining

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the difference but in the description of
the register function that we just

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looked at it states that the constructor can
be called without parameters when it

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actually means without arguments which
justifies our advise not to worry too much

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about the terms and a second thing I want
to point out is the parameter called

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self

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we are going to be covering classes in the next section
actually and you'll learn about the

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difference between functions and methods
but until then when you call a method in

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the same way you do a function as we did
with shelve.open for example in the

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previous section but in the documentation
for method you see that the first

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parameter or argument to a method is self
but you don't have to provide a value

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for it when you calling the method Python
takes care of this for you so just

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ignore self for now and again this will all
be revealed in covered in detail when we

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cover object orientated programming
classes later in the course so that's it

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I'm gonna finish is very long video now
and I'll see you in the next video