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Lecture 2

Printing, Strings, and Constants

Benjamin Dicken

CSc 250 - Spring 2018

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Programming in Python

Using wing101 this semester

Go to https://wingware.com/downloads/wingide-101
Download and install correct version
Open up the program
Ready to start writing some code

If you have not downloaded it, do so now!

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Wing 101

The Wing101 UI look like this
The main text area is where you write your code!

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Wing 101

Should rearrange to look like this
The top area is where you write code
The bottom area is the Python Console. This is where the output of your python programs goes to

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Print!

The first thing we’ll learn how to do is print text to the console
To do this, we are going to use the print function . . .

print("Text to print in here")

print is one of many functions that we will learn about in processing
This will cause the text (not including the quotes) to be printed on the console

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Print!

After print runs, a line-break is added to the console

Like hitting “Enter” in a text editor

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Print!

After print runs, a line-break is added to the console

Like hitting “Enter” in a text editor

Thus, this code:

print("Don’t know much about history")

print("Don’t know much biology")

Produces something different than this code:

print("Don’t know much about history Don’t know much biology")

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Printing some lyrics

Song lyrics are often formatted on multiple lines
Write a simple python program that prints the following to the console:

If I ever took a loss, I learned a lesson

I won't ever think I'm better than the next man

I've been down before the come up, I ain't stressin'

Baby I'm too busy countin' all these blessings

(From “Blessings” by Lecrae)

ICA

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Printing some lyrics

Solution:

print("If I ever took a loss, I learned a lesson")

print("I won't ever think I'm better than the next man ")

print("I've been down before the come up, I ain't stressin'")

print("Baby I'm too busy countin' all these blessings")

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Print!

What is we need to print some very repetitive lyrics?
For example, the entire lyrics to Daft Punk’s “Around the World” is

Around the world, around the world

(x18)

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Print!

One way to print this out would be:

print("Around the world, around the world")

print("(x18)")

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Use a variable

You can actually give a string a “name” and then reference the string using the name, instead of repeating the entire text

lyric = "Around the world, around the world"

print(lyric)

print("(x18)")

This is actually called declaring a variable
We will cover this in more depth in a few lectures

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Printing repetitive lyrics

Write a program that prints out these repetitive lyrics using TWO variables

Yeah, they like the way I do this

When I crank it like a chainsaw

Yeah, they like the way I do this

When I crank it like a chainsaw

(From “Chainsaw” by Family Force 5)

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Printing repetitive lyrics

Solution:

yeah = "Yeah, they like the way I do this"

chain = "When I crank it like a chainsaw"

print(yeah)

print(chain)

print(yeah)

print(chain)

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Use a variable

How about these lyrics?

Right about now The funk soul brother

Check it out now The funk soul brother

Right about now The funk soul brother

Check it out now The funk soul brother

Right about now, 'bout now 'Bout now, 'bout now

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Use a variable

How about these lyrics?

Right about now The funk soul brother

Check it out now The funk soul brother

Right about now The funk soul brother

Check it out now The funk soul brother

Right about now, 'bout now 'Bout now, 'bout now

Where is the repetition?

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Use a variable

How about these lyrics?

Right about now The funk soul brother

Check it out now The funk soul brother

Right about now The funk soul brother

Check it out now The funk soul brother

Right about now, 'bout now 'Bout now, 'bout now

Where is the repetition?

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Use a variable

How about these lyrics?

Right about now The funk soul brother

Check it out now The funk soul brother

Right about now The funk soul brother

Check it out now The funk soul brother

Right about now, 'bout now 'Bout now, 'bout now

Where is the repetition?
There are four repetitive sections, so . . .

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Use a variable

right = "Right about now"

check = "Check it out now"

funk = " The funk soul brother"

Bout = ", 'bout now 'Bout now, 'bout now"

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Use a variable

right = "Right about now"

check = "Check it out now"

funk = " The funk soul brother"

Bout = ", 'bout now 'Bout now, 'bout now"

Now how do we use them?

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Use a variable

right = "Right about now"

check = "Check it out now"

funk = " The funk soul brother"

bout = ", 'bout now 'Bout now, 'bout now"

print(right + funk)

print(check + funk)

print(right + funk)

print(check + funk)

print(right + bout)

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String concatenation

When the plus-sign is placed between two strings this concatenates them together

Puts one after the other

This can be used in printing like we just saw
Or can be used in any case you would use a string

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String concatenation

What will the another1 and another2 variables have in them?

right = "Right about now"

check = "Check it out now"

funk = " The funk soul brother"

bout = ", 'bout now 'Bout now, 'bout now"

another1 = right + right

another2 = funk + another1

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More Strings

Let’s revisit the “Around the world” example:

lyric = "Around the world, around the world"

print(lyric)

print("(x18)")

This is better than the original, but do you think there’s something we could do to make it EVEN BETTER?

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Multiplication

In python the asterisk (*) can be used to repeat (multiply) a string some number of times

class = "CSC 250 - Essential Computing for the Sciences"

print(class * 5)

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Multiplication

In python the asterisk (*) can be used to repeat (multiply) a string some number of times

class = "CSC 250 - Essential Computing for the Sciences"

print(class * 5)

Or . . .

name = "Your name here! " * 3

print(name * 2)

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More Strings

How could we use multiplication to improve upon this?

lyric = "Around the world, around the world"

print(lyric)

print("(x18)")

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More Strings

How could we use multiplication to improve upon this?

lyric = "Around the world, around the world"

print(lyric)

print("(x18)")

Will this work?

lyric = "Around the world, around the world"

print(lyric * 4)

print("(x18)")

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Newline

We can put a line-break (also called a newline) into a string wherever we want with a special two-character sequence: \n
\n Will be replaces with a newline when the string is printed

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Printing with newlines

How could we get the following to print using a single string?

AAA

BBBBBB

CCCCCCCCC

DDDDDD

EEE

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Printing with newlines

Solution:

print("AAA\nBBBBBB\nCCCCCCCCC\nDDDDDD\nEEE")

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More Strings

This is what we really need:

lyric = "Around the world, around the world\n"

print(lyric * 4 + "(x18)")

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Which is better? Why?

print("Around the world, around the world")

print("(x18)")

lyric = "Around the world, around the world\n"

print(lyric * 4 + "(x18)")

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Constant numbers

When we have a number that we want to save and use repeatedly, can store it as a CONSTANT

REPEAT = 4

lyric = "Around the world, around the world\n"

print(lyric * REPEAT + "(x18)")

Constants are typically in all caps
These should be used to store a number that will keep the same value the entire time the program runs

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Dynamic Sizing

Write a program that prints out a tie-fighter
The width of the tie-fighter is sized according to the WIDTH constant

WIDTH = 0

/ \

<-O->� \ /

WIDTH = 5

/ \

<------O------>� \ /

WIDTH = 3

/ \

<----O---->� \ /

ICA