|
LESSON NOTE/GUIDE
|
|
THE
CODE #Pat Campeau #This is our first Python program. print("Hello
world") |
|
EXPLANATION In the above code, the first two
lines that start with a # symbol are comments. They are completely ignored when the
program is executed. The last line uses the print
function (or command) to output a string (or message) to screen. Strings are always placed inside double
quotes. |
PROGRAM
2 – VARIABLE TYPES (int, float, string)
·
Explain that we
should now create a new file for a new program.
·
Create three
variables and set them to integer values and add them up. Output the result.
·
Show how to
output text and the number at once.
·
Do the same for
floating point numbers (float).
·
Do the same for
strings. What happens when you add
strings together?
·
Also show the
comma used in a print statement
|
THE
CODE #1-Integers (int) x = 4 y = 6 answer = x + y print("The
answer is", answer) #2-Floating point numbers (float) a = 4.2 b = 3.1 answer2 = a + b print("The
answer is", answer2) #3-Strings w1 = "hi" w2 = "yo" answer3 = w1 + w2 print("The
answer is", answer3) |
|
EXPLANATION We are using variables for the
first time. Variables allow us to
store information from one line of code and use it in another. We create a variable by giving it a
name and assigning it a value.
Variable names must start with a letter and can contain
numbers. We are considering three types of
variables in the program above:
In the third section, you may
notice that the third line is apparently adding two words together. In Python, this is called string
concatenation. It simply means that both words are glued together to create
on word. |
PROGRAM
3A – USER INPUT (TEXT)
·
Use the input
function to get users to input a string value.
·
Do the greeting
app.
·
Show how type
casting can be used to get a number.
|
THE
CODE name = input("Enter your
name") print("Hello
there", name) |
|
EXPLANATION The input function displays a
message (usually an instruction to the user) and waits until the user
enters a word (or a number) and hits enter.
The value entered is then stored in the name variable. In the second line, we output the
greeting message along with the name that was just entered by the user. |
PROGRAM 3B – USER INPUT (NUMBERS)
·
Get the user to
input numbers.
·
Learn how to
convert (type cast) a value from string to number.
|
THE
CODE num1 = input("Enter a
number") num2 = input("Enter a
number") ans = int(num1) + int(num2) print("The
sum is", ans) |
|
EXPLANATION The first two lines simply get
input from the user. Eventhough the user enters numbers (we hope), the
information is still seen as strings. In the third line, we first convert
each string to its integer value and then we add them up. Note that to convert from string to
int, we use the int() function. The float() function
works similarly. In the final line, we simply output
the sum to screen. |
PROGRAM
4 – BASIC ARITHMETIC
·
Get two numbers
from the user. Remember that by
default, you will get string variables, so you need to type cast them to int
or float.
·
Add them
together and output the value.
·
Multiply them
together and output the result.
·
Divide one from
the other and output the result.
|
THE
CODE num1 = int(input("Enter a
number")) num2 = int(input("Enter a
number")) #Adding numbers ans1 = num1 + num2 print("The
sum is", ans1) #Multiplying numbers ans2 = num1 * num2 print("The
product is", ans2) #Dividing numbers ans3 = num1 / num2 print("The
quotient is", ans3) |
|
EXPLANATION The first two lines simply get
input from the user. Note that we
immediately use the int() functions to make the
inputted data an integer. So our
variables are integers! The rest of the program shows
addition, multiplication and division.
Notice the symbols used. |
PROGRAM
5 – MATH EXPRESSIONS & BEDMAS
·
Write a program
that evaluates different expressions.
Show the effect of BEDMAS.
·
Show how to use
brackets to specify an order of operations.
|
THE
CODE #BEDMAS forces the * to be first x = 1 + 3 * 2 print(x) #Brackets force the + to be first y = (1 + 3) * 2 print(y) #BEDMAS forces the / to be first z = 3 + 4 / 6 + 1 print(z) |
|
EXPLANATION BEDMAS is used to decide the order
of operations. Brackets need to be
used to force a specific operation to be done first. |
PROGRAM
6 – MORE ARITHMETIC (remainder, exponents)
·
Demonstrate the
mod operator %.
·
Demonstrate the
exponentiation operator **.
·
Recall that the
square root is the same as exponent 0.5.
·
Write a program
that outputs the remainder of 100 divided by 3.
·
Then, at the
bottom of the same program, calculate 28.
|
THE
CODE #Exponents print(2**3) print(2**10) #Square root print(100**0.5) #Remainders (mod) print(100 % 3) print(7 % 5) |
|
EXPLANATION We can do exponents in Python by
using the **. So the value of 210
is written as 2**10. The square root of a number is the
same giving that number an exponent of 0.5.
So, 100**0.5 is 10. Do you remember when divisions lead
to an answer along with a remainder.
For example, 12 divided by 5 gave us 2 with a remainder of 2. Oh the good ole days… Well, if we want to know what the
remainder would be for such a divisions, we can
simply use the mod symbol %. So, 12
% 5 gives 2. |