WEBVTT

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So in the previous two videos, we learned
about reading and writing to text files.

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So they're the two modes that you
would use, probably, fairly often.

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And we can also append to a text file
by using an A as the mode for append.

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Now, opening a text file in append
mode causes data to be written to

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the end of the file.

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Without overriding the existing contents.

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In fact these three modes are short for
RT, WT, and AT.

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Or TR, TW, and TA.

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The letters can be specified
either way around.

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So the T stands for
text mode which is the default.

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You don't ask for text or binary.

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Now there's an interesting
link here that you can go to

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to find out more about
the file opening mode.

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So I'm just going to
open that up to show you.

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And this link will be in
the resources section.

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And you can see here the modes on the
screen, so we've got various modes there.

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And you can see if you don't specify mode,

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the default is auto is set to RT to
open a file, a text file, for reading.

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And as it turns out, we'll be looking at
a binary file next in the next video,

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but it's also possible to open a file for
both reading and writing by using plus.

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But that doesn't replace r or w so
you have to use r plus or w plus or such.

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Now mode x on the screen there,

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it can be useful if you expect that file
shouldn't already exist and so it will

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raise an error if you try to create a file
with the same name as the existing one.

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And there can be some situations and
circumstances where that can be useful.

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So before we move on
now to binary files and

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better ways to store variables,
it's time for a challenge.

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So let's go back to our code.

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And we're gonna create a new file,
new path and file,

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we're just gonna call it challenge.

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So the challenge is
going to be as follows.

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And what I'm going to do is I'm just
going to paste the code in Okay so

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there is our challenge.

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So we're going to write a program
to append a times table to our

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in sample dot text.

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So we want the tables from two
to 12 similar to the output

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from the lecture which was in
section six of this course.

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So the first column of numbers
should be right justified.

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As an example, the two times table should
look like you can see there below.

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You can see how that's
formatted going from 1 to 12.

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So again what you're going to want to
do is write a program that's going to

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append these tables, these time tables,
to the Jabberwocky palm and

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sample dot text which you've
worked within the last few videos.

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So pause the video now, go away, and
see if you can come up with that.

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Based on what I talked to you about very
briefly in this video about a pending.

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And you can also refer back to that
documentation page that I showed you

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to find out the appropriate modes and
so forth to use.

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So have a go at that and
when you're ready to come back and

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see a solution or our solution to it
come back and I'll show you that.

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Okay so did you get on?

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Hopefully you managed to get it to work.

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So here's the solution
now we came up with.

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So we're going to start by opening
the file so it's with open,

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and of course it's going to be sample.txt.

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Whoops, I now need to specify the mode,
which is a for

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pending I'm going to call it tables.

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And then I'm going to go 4 I in range,
to 215.

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And then I'm going to put for
J, for J in range 113.

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And then I'm going to print
using replacement field syntax

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Two like so times is two and

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we use a .format which is gonna be i j and
of course i times j.

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And then in the end of it files = tables.

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And then we finish it off with a print

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times 20, files = tables.

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File yet, that should be file.

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That should be it, so just confirming
that our sample got text at the moment

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it's just got the Jabberwocky poem so
I'll just close it down again.

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And if we now run this we don't
get anything output directly

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because we've written everything
to a file not the console.

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But now if I check my sample dot text.

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You can see we've got the times tables,
correctly showing in the end of that file.

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So we've correctly appended to that file.

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Now note that each time that we've
run this program, I run it again.

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And I'll just close it down to open it up,
to make it easier.

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And, we've got the data repeated twice so
its actually come back and done it again.

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Because pent output H time we run the
program in effect starting at the end of

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the file, and if you wanted
to create a new file instead,

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obviously, head back to our code and
change the A to a W.

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And, that would create
the new file each time.

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So, for example, And

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I'll just call name something else so
we don't overwrite the original file.

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And you'll run that.

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You'll see sample two appear
there on the left hand side.

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There's our code.

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143 lines there, and
if we run it again Just to confirm,

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I've still got 143, so it's obviously
creating the file each time.

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So that's it, that's the end of
these three videos on reading and

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writing text files.

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In the next video, we're going to
start looking at binary files,

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which is a different mechanism for
saving different types of data.

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So, see you int hat next video.