Python slide

Keep Calm and Code Python

Let’s Python

Department of Computing!
Faculty of Science!
Silpakorn University


Who am I ?
Kiattisak Anoochitarom!
Graduated from Computer Science at SU, 2013!
Software Developer at Charged Concept Co, LTD.!

!

Skill Sets: iOS, Rails, Node.js, Ruby, Python, Javascript, !
C++, C, Java, Badminton!

!

Contacts:!
macbaszii@gmail.com!
Twitter: @iMacbaszii!
http://www.facebook.com/baszii!
http://www.macbaszii.com!

Who Invented ?

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Guido van Rossum!

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Dutch!

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2005 - 2012 at Google inc.!

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2013 at Dropbox inc.

Langauge Characteristic
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Open Source (Python Software Foundation)

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Rapid Development

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Rapid Development

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Short and Readable Code

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Rapid Development

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Indentation!

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Rapid Development

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Indentation!

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Strong and Dynamic Typing

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Rapid Development

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Indentation!

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Strong and Dynamic Typing

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Interpreter Style

PEP - 8
Python Coding Style Guide
http://www.python.org/dev/peps/pep-0008/

Input & Output
name = raw_input()
print "Hello, %s" % (name)
print "Hello, " + name
x = input()
y = input()
print x * y

Input & Output
name = raw_input()
print "Hello, %s" % (name)
print "Hello, " + name
x = input()
y = input()
print x * y

Hands - on!!

Data Type
Dictionary

String
Integer

Boolean
Floating Point

List

Set
None

Class Instance

Data Type
Dictionary
sentence = 'this is a cat'

Integer
Boolean
Floating Point

List

Set
None

Class Instance

Data Type
Dictionary
x = 20

Boolean
Floating Point

List

Set
None

Class Instance

Data Type
Dictionary
x = 20
you_love_me = True

Floating Point

List

Set
None

Class Instance

Data Type
Dictionary
x = 20
you_love_me = True

pi = 3.1415927

List

Set
None

Class Instance

Data Type
Dictionary
x = 20
you_love_me = True

pi = 3.1415927

List

Set
nothing = None

Class Instance

Data Type
Dictionary
x = 20
you_love_me = True

pi = 3.1415927

even_numbers = [2, 4, 6, 8, 10]

Set
nothing = None

Class Instance

Data Type
Dictionary
x = 20
you_love_me = True

pi = 3.1415927

even_numbers = [2, 4, 6, 8, 10]

odd_numbers = {1, 3, 5, 7, 9}

nothing = None

Class Instance

Data Type
profile = { 'name': 'Bas',
'email': 'macbaszii@gmail.com'}
x = 20
you_love_me = True

pi = 3.1415927

even_numbers = [2, 4, 6, 8, 10]

odd_numbers = {1, 3, 5, 7, 9}

nothing = None

Class Instance

Data Type
profile = { 'name': 'Bas',
'email': 'macbaszii@gmail.com'}
x = 20
you_love_me = True

pi = 3.1415927

even_numbers = [2, 4, 6, 8, 10]

odd_numbers = {1, 3, 5, 7, 9}

nothing = None

my_car = Car('Lamborghini',
'Aventador LP 700-4', 'White')

Math Operator
x = 10
y = 20
x + y
x - y
x * y
x / y
x % y
x**y
x += y
y *= x

Math Operator
x = 10
y = 20
x + y
x - y
x * y
x / y
x % y
x**y
x += y
y *= x

## Tips ##
int + int = int
int**(-int) = float
int / float = float
string + string = concat_string
string * int = multiply_string
list + list = list

Comparison Operator
x = 10
y = 20
x
x
x
x
x
x
x

> y
>= y
< y
<= y
== y
!= y
is y

Comparison Operator
x = 10
y = 20
x
x
x
x
x
x
x

> y
>= y
< y
<= y
== y
!= y
is y

# Chain Comparison
5 < x < y
1 < y < 100
# Contains Operator
prime = [2, 3, 5, 7, 11]
9 in prime # False
'cat' in sentence # True

Logical Operator
Although Python have & and | (pipe) to do logical operation !
but it isn’t readable and it will confuse with other symbol. !
But Python have special symbols to do logical operation that is …

Logical Operator
Although Python have & and | (pipe) to do logical operation !
but it isn’t readable and it will confuse with other symbol. !
But Python have special symbols to do logical operation that is …

and, or

Range and Lazy Generator
range(10)
# [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
range(3, 10)
# [3, 4, 5, 6, 7, 8, 9]
range(1, 20, 3)
# [1, 4, 7, 10, 13, 16, 19]
xrange(10)
xrange(3, 10)
xrange(1, 20, 3)

Conditional Statement
if
number = input("Enter Number: ")
if number > 0:
print "Number is Positive"
elif number < 0:
print "Number is Negative"
else:
print "Number is Zero"

if
if number > 0:
elif number < 0:
else:
result = (number % 2 == 0) ? 'Even' : 'Odd'

if
if number > 0:
elif number < 0:
else:
result = 'Even' if number % 2 is 0 else 'Odd'

Iteration Statement
for
for i in xrange(1, 11):
print i**2

Iteration Statement
for
print i**2
socials = ['Facebook', 'Twitter']
for social in socials:
print 'I played %s' % social

Iteration Statement
for
print i**2
message = 'Hello, CPSU'
for letter in message:
print letter

Iteration Statement
for
print i**2
message = 'Hello, CPSU'
for letter in message:
print letter

# Endless Loop #
while True:
# Do something

Problem#1: Most Letter Count
Hint: You can get list of alphabets with this code

import string
!

alphabets = list(string.lowercase)

Function
def function_name(params):
# Do something
# Do anything

Function
# Do something
# Do anything
def fibonacci(n):
fibo = 0
for k in xrange(0, int(math.floor((n - 1) / 2)) + 1):
fibo += math.factorial(n - k - 1) /
(math.factorial(k) * math.factorial(n - k - 1 - k))
return fibo

Function
# Do something
# Do anything
def fibonacci(n):
fibo = 0
for k in xrange(0, int(math.floor((n - 1) / 2)) + 1):
fibo += math.factorial(n - k - 1) /
(math.factorial(k) * math.factorial(n - k - 1 - k))
return fibo
def colorMultiply(r, g=0, b=0):
return [ r * 3.14159,
g * 1.414,
b * 3.27 ]

Built-in Functions
http://docs.python.org/2/library/functions.html

Problem#2: Make a
Palindrome StringgnirtS emordnilaP
Way Too Long Words
Sometimes some words like "localization" or "internationalization" are so long that writing them
many times in one text is quite tiresome.!
Let's consider a word too long, if its length is strictly more than 10 characters. All too long words should
be replaced with a special abbreviation.!
This abbreviation is made like this: we write down the ﬁrst and the last letter of a word and between
them we write the number of letters between the ﬁrst and the last letters. That number is in decimal
system and doesn't contain any leading zeroes.!
Thus, "localization" will be spelt as "l10n", and "internationalization will be spelt as “i18n".!
and make Palindrome from that word after that :)

http://codeforces.com/problemset/problem/71/A

Indexing and Slice
message = 'Hello, world'
message[0] # H
message[len(message) - 1] # d
message[-1] # d

Indexing and Slice
message[0] # H
message[-1] # d
fibo = [1, 1, 2, 3, 5, 8, 13, 21, 34]
fibo[:5] # [1, 1, 2, 3, 5]
fibo[2:] # [2, 3, 5, 8, 13, 21, 34]
fibo[3:6] # [3, 5, 8, 13]
fibo[::2] # [1, 2, 5, 13, 34]

Indexing and Slice
message[0] # H
message[-1] # d
fibo = [1, 1, 2, 3, 5, 8, 13, 21, 34]
fibo[:5] # [1, 1, 2, 3, 5]
fibo[2:] # [2, 3, 5, 8, 13, 21, 34]
fibo[3:6] # [3, 5, 8, 13]
fibo[::2] # [1, 2, 5, 13, 34]
fibo[::-1] # ???
message[::-1] # ???

String and Collections methods

Demo!

List Comprehensive
The Other way to create and manipulation Python’s List

List Comprehensive

[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

List Comprehensive

[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
squares = []
for x in range(10):
squares.append(x**2)

List Comprehensive

[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
squares = [x**2 for x in range(10)]

List Comprehensive

[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

set1 = [1, 2, 3]
set2 = [3, 1, 4]

List Comprehensive

[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

set1 = [1, 2, 3]
set2 = [3, 1, 4]
combs = []
for x in set1:
for y in set2:
if x != y:
comb.append((x, y))

List Comprehensive

[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

set1 = [1, 2, 3]
set2 = [3, 1, 4]
combs = [(x, y) for x in set1 for y in set2 if x != y]
[(1, 3), (1, 4), (2, 3), (2, 1), (2, 4), (3, 1), (3, 4)]

Working with File
open('filename', mode)
# r: open file for read
# w: open file for write
# a: open file for append

Working with File
f = open('data.txt', r)
f.read() # read file to string
f.readline() # read file for one line
f.readlines() # read file to lines

Working with File
f = open('data.txt', r)
f.read() # read file to string
f.readline() # read file for one line
f.readlines() # read file to lines
f.write('this is a cat') # write string to file
f.writelines([list of line]) # write lines to file

Object Oriented Programming
Class

Class

Instance

class Book:
def __init__(self, name, size):
self.name = name
self.size = size
class BookStack:
def __init__(self):
self.books = []
self.top = 0
def push(self, book):
self.books.append(book)
self.top += 1
def pop(self):
self.top -= 1
return self.books.pop()

!

Unit Test
import unittest

! TestBookStack(unittest.TestCase):
class

# when book is created, it can return name, size
def test_book_created(self):
hunger_book = Book('The Hunger Games', 4)
self.assertEqual(hunger_book.name, 'The Hunger Games')
self.assertEqual(hunger_book.size, 4)
# when Book Stack is created / top is 0
def test_book_stack_created(self):
book_stack = BookStack()
self.assertEqual(book_stack.top, 0)
self.assertEqual(book_stack.books, [])
# when push book / top increase by one
def test_book_stack_push(self):
book_stack.push(hunger_book)
self.assertEqual(book_stack.books[0].name, 'The Hunger Games')
# when pop book / top decrease by one
def test_book_stack_pop(self):
harry_book = Book('Harry Potter', 3)
book_stack.push(harry_book)
present_size = book_stack.top
poped_book = book_stack.pop()
self.assertEqual(book_stack.top, present_size - 1)
self.assertEqual(poped_book.name, 'Harry Potter')

if __name__ == '__main__':
unittest.main()


Problem#3: Books
Instruction:!
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- Using TDD!!
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- Each Book have a name, size!
!
- Books have size and all of book!

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Test case:!
!
- paste the new book on top!
!
- pick a book at top of books!
!
- when paste new book you must take a
larger book to below!
!
- program can tell a present Books size

Migrate to Python 3

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print is function instead of
statement!

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input()!

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range instead of xrange!

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more usage on lazy generator

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