Beginners Programming Course

Lesson one

Ismail S

November 2018

Who am I?

Studied maths & physics at Leeds uni
Learnt to program in my spare time, initially via Youtube
Got a job at a software consultancy
Gets paid money to program

Who are you?

Introductions

Comms

Email, WhatsApp?

Why am I doing this?

I want to see if I can teach people to program
To introduce you guys to a new skill (maybe a new career)

What we will cover

Basics of programming in Python eg:
- Numbers, strings etc
- Variables
- Functions
- Lists, dictionaries
Making basic programs

What we won’t cover

Classes (unless we do well with everything else)
Making websites
Making apps
Making anything with a graphical interface
Loads of other stuff
But you’ll take the first steps to being able to do these things

How I’ll teach

We’ll work through Automate the Boring Stuff with Python (with a few tweaks/additions)
Work at your pace, but ideally everyone stays roughly together
At some points, I’ll present some stuff lecture-style
I go around and help people

What I expect of you

Be respectful (of everyone).
- This includes being on time (let me know in advance if you’ll be late).
Ask questions, no matter how basic they may seem (but also try and figure things out yourself)
I may ask you to look things up yourselves - this is intentional, I’m not being lazy

Homework?

This isn’t school
But doing stuff outside of the lessons will help. A lot.
You can only help yourself.

Exam

There isn’t one
But depending on how things go, I may set a final (challenging-ish) exercise

Warning

Programming is hard (it requires you to think)
But, if done right, it can be enjoyable/addictive
Programming is not for everyone (but give it a decent shot before giving up)
However, software is eating the world

A little bit of background

What are computers?

Machines that follow instructions
Example instructions:
- Add these 2 numbers together
- Check if this number is equal to 0
- Go (jump) to another instruction
- Store this number in this place in memory

The instructions computers follow aren’t too fancy or complicated
But computers can perform these instructions very fast
- By fast, we mean billions of instructions a second (1 billion = 1 000 000 000)
And computers don’t get tired or complain. Ever.

What is programming?

Writing the instructions that computers can then follow (execute)
The language that computers understand is very boring and tedious to write instructions in
So we use easier languages to write the instructions in (like Python)

Then we either:
- Run this through another program to turn it into the instructions a computer understands. Like translating from eg French to English. Except we get a program to do it for us.
- Run a virtual computer on top of the actual computer. The virtual computer understands our instructions.
  - I know, it sounds crazy, but it does work
  - This is how we’ll run our Python code
A program is just a bunch of instructions for a computer to follow

What is Python?

A good programming language for beginners
One of the most popular programming languages in industry
Named after Monty Python

Self-directed part

Now let’s go over what you learned

Numbers

>>> 1 + 1
2
>>> 1.1 + 2
3.1
>>> 3 - 2
1

>>> 5 * 2
10
>>> 5.5 * 2
11.0

>>> 10 / 2
5
>>> 7 / 2
3.5
>>> 7 // 2
3

Strings

>>> 'this is a string'
'this is a string'
>>> "this is a string"
'this is a string'

>>> 'hello' * 2
'hellohello'
>>> 'hello' + ' ' + 'world'
'hello world'

Variables

>>> blah = 50
>>> blah
50
>>> blah = 'something else'
>>> blah
'something else'

>>> first  = 'something'
>>> second = 'else'
>>> first + " " + second
'something else'

Print function

The print function takes something and prints it to the screen
print('like this')
print(50)
print('or even ' + 'like this')

Other functions

len takes a string and returns the length
input asks the user for input and returns it
int turns things into an integer
str turns things into a string

Example code

x = "This is some Python code"
print(x)

print("And this is some more Python code")
some_input = input()
print("You just typed: " + some_input)

Lesson 2 - Flow Control

Booleans

>>> True
True
>>> False
False
>>> x = True
>>> x
True

>>> True == True
True
>>> False == True
False
>>> True != False
True

Comparing numbers and strings

>>> 23 == 'a string'
False
>>> 23 == '23'
False
>>> 23 == int('23')
True

Comparing numbers

>>> 2 < 4
True
>>> 4 <= 4
True
>>> 4 < 4
False
>>> 3.2 > 3.123
True

`and`, `or` and `not`

`and`

>>> True and True
True
>>> True and False
False
>>> False and False
False

Truth table

First	Second	Result
`True`	`True`	`True`
`True`	`False`	`False`
`False`	`True`	`False`
`False`	`False`	`False`

`or`

>>> True or True
True
>>> True or False
True
>>> False or False
False

Truth table

First	Second	Result
`True`	`True`	`True`
`True`	`False`	`True`
`False`	`True`	`True`
`False`	`False`	`False`

`not`

>>> not True
False
>>> not False
True

Truth table

First	Result
`True`	`False`
`False`	`True`

Examples

>>> x = 5
>>> 1 < x and x < 7
True
>>> not (1 < x)
False
>>> (x == 4) or (not (x >= 3))
False

Control Flow

`if` statements

>>> name = 'Ismail'
>>> if 'Ismail' == name:
    print('My name is Ismail!')


My name is Ismail!

>>> name = 'Adam'
>>> if 'Ismail' == name:
    print('My name is Ismail!')
else:
    print('My name is not Ismail')


My name is not Ismail

>>> name = 'Mohammed'
>>> if 'Ismail' == name:
    print('My name is Ismail!')
elif len(name) == 8:
    print('My name is 8 letters long')
else:
    print('My name is not Ismail and doesn\'t have 8 letters')


My name is 8 letters long

`while` loops

>>> x = 0
>>> while x < 4:
    print('x is ' + str(x))
    x = x + 1


x is 0
x is 1
x is 2
x is 3

>>> while True:
    print('Hello!')


Hello!
Hello!
Hello!
Hello!
Hello!
...

>>> while True:
    number = input('Please enter a number: ')
    if int(number) == 12:
        print('You guessed the number!')
        break
    print('You guessed incorrectly. Try again.')


Please enter a number: 1
You guessed incorrectly. Try again.
Please enter a number: 3
You guessed incorrectly. Try again.
Please enter a number: 12
You guessed the number!

>>> x = 0
>>> while x < 4:
  print('x is ' + str(x))
  print('x is less than 4')
  x = x + 1
  if x > 2:
    continue
  print('x is also less than 2')


x is 0
x is less than 4
x is also less than 2
x is 1
x is less than 4
x is also less than 2
x is 2
x is less than 4
x is 3
x is less than 4

`for` loops

>>> for i in range(5):
    print(i)


0
1
2
3
4

This is equivalent to:

>>> i = 0
>>> while i < 5:
    print(i)
    i = i + 1


0
1
2
3
4

Modules

Modules are collections of functions and other stuff
You have to import a module, then you can use the things that are in it

Importing modules

>>> import sys
>>> sys.exit()

>>> from sys import exit
>>> exit()

>>> from sys import *
>>> exit()

Importing in this way can make code confusing

Lesson 3 - Functions

Example function

def hello():
  print("We're in a function")
  print("And we're still in it")
  print('And this is the last line')

What can functions do?

Functions can:

take 1 or more inputs
return 1 or more outputs (more than 1 output will be covered later)
do anything that can be done outside functions
- eg print to screen, get input from the user, add numbers etc

def anotherFunc(x, y):
  print('We're inside this function')
  return x + (y * y)

`None`

None is the only value of type NoneType
If a function doesn’t execute a return statement, then None is implicitly returned

>>> def nn():
    print('test')


>>> x = nn()
test
>>> print(x)
None

Keyword arguments

>>> print('this', 'gets', 'spaced', 'out', sep = '   ')
this   gets   spaced   out

Local & global scope

Variables assigned inside a function exist in the local scope of that function
Variables assigned outside all functions exist in the global scope

Local scopes are created every time a function is called
Scopes sound confusing at first, but with practice, they become intuitive

x = 5

def some_func():
  print(x) # Will print 5

x = 5

def some_func():
  x = 7

print(x) # Will print 5

Try not to do this to avoid confusion

x = 5

def some_func():
  global x
  x = 7

print(x) # Will print 7

In practice, we rarely use global as it makes code confusing

def some_func():
  x = 7
  some_other_func()

def some_other_func():
  print(x)

some_func() # Get an exception
# as some_other_func doesn't
# have x in it's local scope

Exception handling

def foo(x, y):
  try:
    return x / y
  except ZeroDivisionError:
    print('Tried to divide by zero')
    print('Returning 0')
    return 0

def bar(x, y, operation):
  try:
    return operation(operation(x, y), y)
  except Exception:
    print('Got an exception whilst trying to run operation')

Beginners Programming Course

Who am I?

Who are you?

Comms

Why am I doing this?

What we will cover

What we won’t cover

How I’ll teach

What I expect of you

Homework?

Exam

Warning

A little bit of background

What are computers?

What is programming?

What is Python?

Self-directed part

Now let’s go over what you learned

Numbers

Strings

Variables

Print function

Other functions

Example code

Lesson 2 - Flow Control

Booleans

Comparing numbers and strings

Comparing numbers

and, or and not

and

Truth table

or

Truth table

not

Truth table

Examples

Control Flow

if statements

while loops

for loops

Modules

Importing modules

Lesson 3 - Functions

Example function

What can functions do?

None

Keyword arguments

Local & global scope

Exception handling

`and`, `or` and `not`

`and`

`or`

`not`

`if` statements

`while` loops

`for` loops

`None`