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In this video, we're going to create a
function that'll let us print text

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with different effects. I'll include
escape codes for the main colors,

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as well as bold, underline
and inverted text. Now I

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mentioned in the last video, that
these escape codes were horrible.

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Something like backslash n is easy
to type and quite easy to remember.

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The codes we need, aren't. I'm not
going to ask you to type them in,

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and heck, I'm not even going to type them
in myself. You'll find them in the

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colour_codes.txt file, in the
resources for this video. We need

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to create a new Python file.
We'll go ahead and do that in our

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current project. I'm going to call this
one colour_print.py.

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Alright, I'm going to paste in
the contents of that text file.

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So the escape sequences are defined
in a series of Python constants.

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We can define them once and then use the
friendlier names, and that's much better

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than remembering that red is escape, open
square bracket, three, one, m.

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Those ANSI escape sequences on lines 2
through 14, start with an escape code,

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followed by an opening square bracket.
So that tells the terminal that the next

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few characters will be special commands,
that it should perform.

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All you have to do to use these escape
sequences is print them to a terminal,

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that understands the ANSI sequences. The
good news is that the IntelliJ run

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window does understand them.
So let's have a go at doing that.

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On line 16, I'm going to type
print parentheses RED comma

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and in double quotes, this will be in red.

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Okay, when I run this - and I'll just move
this run window down to the bottom.

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Alright, so you can see
that that's in red.

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Alright, so our text printed in red, as
you can see, in the IntelliJ run terminal.

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What's not obvious, is that
all output is now red.

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So if I add another line
- let's do that;

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print parentheses and so is this.
and if we run this,

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even though we didn't specify
red this time, the output

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is still red. The changes we
make to the colors, etc,

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will stay in effect until we cancel them.
Now we can reset the text effects,

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by printing the reset sequence. That's
on line 10, as you can see there.

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It's going to be a bit tedious doing
that every time, so this sounds like a

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good use for a function.
So I'm going to delete those two lines

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of output there, on lines
16 and 17, and replace that

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with a function declaration. I'm going to
call this function colour_print,

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so def colour_print, and in parenthesis,

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text colon space str comma effect
colon str. We're going to close it

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with a right parentheses,
and it returns None. So we've got our

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arrow, our dash and a greater than,
None and a colon.

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And you can see that I've annotated the
function. It takes the text to print, a

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string, as its first argument,
and the effect we want, again

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as a string, for the second one.
It's returning None because it doesn't

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return anything useful. The function prints
to the screen - it doesn't return a value.

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Alright, so I'd better document that.

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So I'm going to do just that with a Docstring, so

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three double quotes again. I'll press
enter there, and I'll close the run pane

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so you can see it a bit better. And
we're going to print - I'm going to use my

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backticks again - text using the ANSI

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sequence, or sequences rather,
to change colour, etc.

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In terms of the parameters, we've got
text, which is The text to print,

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and effect, well that's the effect we want,

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and it's one of the constants

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defined at the start of this module.

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Alright, I'm going to remove return because,
in fact, we're not returning anything.

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Okay, so the body of the
function will be quite simple.

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We want to print the ANSI escape
sequence, then the string that was passed

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into the function,
then the reset sequence. So let's start

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by building up the string using dot
format and printing it.

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Notice before I do that, I'm going to add
another line here, line 15, because

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remember, we want to have two blank
lines between the start and ending

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of a function, definition.
Alright, so line 25 now, I'm going to

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type output underscore string is equal
to, and in double quotes, we want

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three replacement strings.
So zero in curly braces, one in curly

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braces and two in curly braces, and we've got our

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double quote dot format, and
in parentheses, effect, text

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comma then reset, which is our constant,
defined on line 10. Okay, so we've

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defined our output string,
let's print it now; print output_string.

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Alright, so let's add some
code here - some test code.

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We're remembering here,
to add two blank lines

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after the end of our function.
So line 29, I'm going to paste in some

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code here - also available
in the resources section.

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So you can see that we're accessing our
new function, but on line 31, I've used

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the built-in print function to print some text.

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That tests that our function has
correctly reset the terminal to the

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default colour.
So run the program now and marvel

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at what we've done.

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So that's pretty cool, and we can make
our output more interesting.

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If you didn't get the different colours
and effects, don't worry. As I said, we'll

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be making a small change
so this code works for you,

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very soon. Our function isn't perfect,
though. There's no way to print yellow

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and bold, or blue and inverted, for example.

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And that's easily done, but we need
to know a bit more about functions.

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We haven't covered how to
write functions that take a variable

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number of arguments, and that's what we
need here. Once we've covered star args,

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we'll come back to this function and
improve it. We'll be doing that a bit later.

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Alright, so make sure you test the Docstring,

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and experiment using this
function, and in the next video,

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we'll run this code the way that our
users will run it. That's a very

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important test, and we'll see 
that it doesn't work on Windows.

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See you in the next video.