Class 4A: Introduction to Programming in Python
Contents
Class 4A: Introduction to Programming in Python¶
We will begin at 2:00 PM! Until then, feel free to use the chat to socialize, and enjoy the music!
Firas Moosvi
Class Outline:¶
1st hour - Introduction to Python
Announcements (2 mins)
Introduction (3 mins)
Writing and Running Code (15 min)
Interpreting Code (15 min)
Review and Recap (5 min)
Learning Objectives¶
Look at some lines of code and predict what the output will be.
Convert an English sentence into code.
Recognize the order specific lines of code need to be run to get the desired output.
Imagine how programming can be useful to your life!
Part 1: Introduction (5 mins)¶
Addition¶
4 + 5 +2
11
# Subtraction
4-5
-1
# Multiplication
4*5
20
# Division
10/2
5.0
# Square, cube, ...
2**3
8
# Squareroot, Cuberoot, ...
4**(1/2)
2.0
Assigning numbers to variables¶
You can assign numbers to a “variable”.
You can think of a variable as a “container” that represents what you assigned to it
There are some rules about “valid” names for variables, we’ll talk about the details later
Rule 1: Can’t start the name of a variable with a number!
General guideline for now: just use a combination of words and numbers
Demo (side-by-side)¶
# Two numbers
num1 = 4000000000000
num2 = 8
print(num1,num2)
4000000000000 8
# Multiply numbers together
num1*num2
32000000000000
Assigning words to variables¶
You can also assign words and sentences to variables!
Surround anything that’s not a number with double quotes ” and “
mysentence = "This is a whole sentence with a list of sports, swimming, tennis, badminton"
print(mysentence)
This is a whole sentence with a list of sports, swimming, tennis, badminton
Using Python to work with words¶
Python has some nifty “functions” to work with words and sentences.
Here’s a table summarizing some interesting ones, we’ll keep adding to this as the term goes on.
Task |
Function |
|---|---|
Make everything upper-case |
|
Make everything lower-case |
|
Capitalize first letter of every word |
|
Count letters or sequences |
|
Demo (side-by-side)¶
mysentence
'This is a whole sentence with a list of sports, swimming, tennis, badminton'
# split on a comma
mysentence.split(',')
['This is a whole sentence with a list of sports',
' swimming',
' tennis',
' badminton']
# make upper case
mysentence.upper()
'THIS IS A WHOLE SENTENCE WITH A LIST OF SPORTS, SWIMMING, TENNIS, BADMINTON'
# make lower case
mysentence.lower()
'this is a whole sentence with a list of sports, swimming, tennis, badminton'
# count the times "i" occurs
mysentence.count('i')
8
# count two characters: hi
mysentence.count('hi')
1
mysentence2 = " Hello. World ..... "
mysentence2
' Hello. World ..... '
mysentence2.strip(' ')
'Hello. World .....'
mysentence2.replace(' ','^')
'^^^^^Hello.^^^^^World^.....^^^^^'
Part 3: Interpreting code (15 mins)¶
Q1: Interpret Code¶
Look at the following code chunk, can you predict what the output will be?
some_numbers = [1, 50, 40, 75, 400, 1000]
for i in some_numbers:
print(i*5)
A. Prints 6 random numbers.
B. Prints the 6 numbers in some_numbers.
C. Prints the 6 numbers in some_numbers multiplied by 5.
D. I don’t know.
# Let's try it!
some_numbers = [1, 50, 40, 75, 400, 1000]
for i in some_numbers:
print(i*5)
5
250
200
375
2000
5000
Q2: Interpret Code¶
Look at the following code chunk, can you predict what the output will be?
some_numbers = [1, 50, 40, 75, 400, 1000]
for i in some_numbers:
if i > 50:
print(i/5)
else:
print(i)
A. Prints the 6 numbers in some_numbers.
B. Prints the number in some_numbers if it is less than or equal to 50, otherwise prints the number divided by 5.
C. Prints the number in some_numbers if it is greater than 50, otherwise prints the number divided by 5.
D. I don’t know.
# Let's try it!
some_numbers = [1, 50, 40, 75, 400, 1000]
for i in some_numbers:
if i > 50:
print(i/5)
else:
print(i)
1
50
40
15.0
80.0
200.0
Q3: Interpret Code¶
Look at the following code chunk, can you predict what the output will be?
some_numbers = [1, 50, 40, 75, 400, 1000]
def process_number(number):
return (number**2)/10
for i in some_numbers:
if i > 50:
print(process_number(i))
A. Prints the number in some_numbers if it is greater than 50, otherwise prints nothing.
B. Prints the output of the process_number() function applied to some_numbers.
C. Prints the output of the process_number() function if the original number is greater than 50, otherwise prints nothing.
D. I don’t know.
# Let's try it!
some_numbers = [1, 50, 40, 75, 400, 1000]
def process_number(number):
return (number**2)/10
for i in some_numbers:
if i > 50:
print(process_number(i))
562.5
16000.0
100000.0
Q4: Order matters!¶
Suppose you are asked to complete the following operation:
Take the number 5, square it, subtract 2, and then multiply the result by 10
Does the order of the operations you do matter? Yes!
# Let's try it:
((5**2) -2)*10
230
# Here is the same operation as above but in multiple lines
number = 5
number = number**2
number = number - 2
number = number * 10
print(number)
230
Q5: Parson’s problem¶
A Parson’s Problem is one where you are given all the lines of code to solve the problem, but they are jumbled and it’s up to you to get the right order.
A student would like to get this as the final output of some code that they are writing:
3 is smaller than, or equal to 10.
4 is smaller than, or equal to 10.
5 is smaller than, or equal to 10.
6 is smaller than, or equal to 10.
7 is smaller than, or equal to 10.
8 is smaller than, or equal to 10.
9 is smaller than, or equal to 10.
10 is smaller than, or equal to 10.
11 is bigger than 10!
12 is bigger than 10!
13 is bigger than 10!
14 is bigger than 10!
15 is bigger than 10!
Here are ALL the lines of code they will need to use, but they are scrambled in the wrong order. Can you produce the desired output?
Hint: Pay attention to the indents!
my_numbers = [3,4,5,6,7,8,9,10,11,12,13,14,15]
for i in my_numbers:
if i > 10:
print(i,'is smaller than, or equal to 10.')
else:
print(i,'is bigger than 10!')
my_numbers = [3,4,5,6,7,8,9,10,11,12,13,14,15]
for i in my_numbers:
if i > 10:
print(i,'is bigger than 10!')
else:
print(i,'is smaller than, or equal to 10.')
3 is smaller than, or equal to 10.
4 is smaller than, or equal to 10.
5 is smaller than, or equal to 10.
6 is smaller than, or equal to 10.
7 is smaller than, or equal to 10.
8 is smaller than, or equal to 10.
9 is smaller than, or equal to 10.
10 is smaller than, or equal to 10.
11 is bigger than 10!
12 is bigger than 10!
13 is bigger than 10!
14 is bigger than 10!
15 is bigger than 10!
Congratulations!!¶
You have just shown that you can program!
Over 75% of the course programming content will be focused on details of the things you’ve seen above:
Numbers and Strings
Loops and Conditionals
Functions
If you followed along with most of what we covered, you’re in good shape for this course
