1. Python Bootcamp - C4Dlab
SCI labs, University of Nairobi
Nov 24th 2013
Kenny Rachuonyo

2. Introduction to Python
Features of Python
● Simplicity - pseudocode
● Free and Open Source - community
● High-level – no low-level mngt
● Interpreted – run from source
● Object-Oriented – simple to use
● Extensible – C/C++

3. Features (cont.)
● Embeddable – games, graphics,
● Extensive Libraries (batteries included) – data
compression, OS, Networking, Internet,
Multimedia, Graphics

4. Python in the Industry
Web
● Google – Youtube, backend tasks..
● Reddit – news aggregation site
● Disqus – commenting service
● Numerous web frameworks – django, Zope,
webapp2, web.py, pyramid, flask

5. Python in the Industry
Desktop
● Games – Counterstrike, Civilization IV
● Cinema 4D – Graphics
● Dropbox
● GUI frameworks – PyGTK, PyQT,

6. Python in the Industry
Scientific Computing
● NASA
● Packages: Scipy, Numpy, Matplotlib,

7. Python in the Industry
Mobile
● Nokia Symbian Series 60
● Android – Scripting Layer for Android
● Blackberry
● Kivy – cross-platform: iOS, Android, Linux,
Windows, Mac

8. Python Basics
● The interpreter
– Installation
– Windows (set path)
● Datatypes: int, str, float, lists, tuples,
dictionaries
● Basic I/O

9. Python Basics
● Variables
– Dynamically-typed vs statically-typed
>>> x = 1
>>>y = “hello”
– Strongly-typed
>>> x + y
● Type function
>>> type(x)
● Integer vs float
>>> z = 1.0

10. Python Basics
Operator Operation
+ Addition
- Subtraction
/ Division
* Multiplication
** Power
% Modulus

11. Python Basics
● How will this be evaluated?
>>>X = 1 + 2 – 3 ** 4 * ( 5+6)

12. Python Basics
● Operator Precedence rules
Parenthesis
Power
Multiplication
Addition
Left-to-right

13. Python Basics
● Integer division
>>> 4/2
>>> 5/2
● Mixing integer and floats
>>> 5/2.0
● Casting between integer and floats
>>> float(5)
>>>int(5.0)

14. Python Basics
Strings – sequence of characters
>>> s = “hello world”
● Looking inside
>>> s[0]
● Concatenation
>>> s = ”hello ” + “world”
● Finding length
>>> len(s)
● Slicing
>>> s = s[0:5]

15. Python Basics
Handy String functions
● find
>>> s.find('e')
● Replace
>>> n = s.replace('e', 'a' )
● Make upper, lower
>>> u = s.upper()

16. Python Basics
● Get the second word 'world' by slicing
>>> “hello, world”[x:y]

17. Python Basics
Lists – collection of values
● Declaring
>>> l = list()
>>> l = []
● Can hold different types
>>> l = [1, 'a', [2, 3], 4]
>>> l[2]
● Appending
>>> l.append('an item')
>>>del(l[2])

18. Python Basics
Lists – collection of values
● Getting length
>>> len(l)
● Slicing
>>> l[1:4]
● Converting between strings and lists
>>> strlist = “this is a string”.split('s')
>>> “z”.join(strlist)

19. Python Basics
● Append an item to the list within the list
>>> l = [1, 'a', [2, 3], 4]
>>> l = [1, 'a', [2, 3, 5], 4]

20. Python Basics
● Handy functions
Sum
>>> sum([2, 3, 4])
Max
>>> max([2, 3, 4])
Min
>>> min([2, 3, 4])

21. Python Basics
Dictionaries – key, value pairs
Associative array, hash table
● Declaring
>>> d = dict()
>>> d = {}
● Setting a value
>>> d[“event”] = “bootcamp”
>>> d = {“event” : “bootcamp” }
● Getting a value
>>> d[“event”]

22. Python Basics
Mutability
● Mutable – can change
– Lists, dictionary
● Immutable – cannot change
– Strings, tuples
● Try set, del..

23. Python Basics
Casting – numbers and strings
● Strings and numbers
>>> int(“234”)
>>> str(234)

24. Python Basics
● Importing modules
>>> import math
>>> math.sqrt(4)
>>> from math import sqrt
>>> sqrt(4)
● dir() function
>>> dir(math)

25. Python Basics
● Basic I/O
>>> name = raw_input()
>>> name = raw_input(“Name: “)
Input numbers:
>>>age = raw_input(“Age: “)
>>>age = int(raw_input(“Age: “))

26. Modules
● Interactive mode vs modules
● Indentation

27. Boolean Values
● True
>>> 1 < 2
● False
>>> 1 > 2
● Also evaluate to False:
“”, [], {}, 0

28. Loops
● While loop – while condition is true
x=0
while x < 10:
print x
x=x+1
● For loop – loops over items
words = ['this' , 'is', 'a', 'list']
for w in words:
print w
● Loop over strings, dictionaries..
● Range() function
>>> range(3)
>>> range(0, 10, 2)

29. Functions
● Defining functions
def say_hello():
print “hello”
● Calling functions
say_hello()
● Parameters
def sub(a, b):
s=a-b
return s
sub(b=3, a=2)

30. Functions
● Commenting in Python
def sub(a, b):
d = a – b #subtracts b from a
return d
● Doc strings
def sub(a, b):
“””this functions takes in 2 integers and returns their
difference”””
d=a–b
return d

31. File I/O
● Writing to a file
f = open('text.txt', 'wb')
f.write('This is a line.n')
f.close()
● Reading a file
f = open('text.txt', 'rb')
stream = f.read()
f.close()

32. Accessing the Web
● Establishing a connection
– sockets
● Requests and Responses
– GET, retrieve a webpage
– POST, save data
● Download a webpage
fopen = urllib.urlopen(“http://www.google.com”)
data = fopen.read()

33. Demo
● Web demo
● Scientific computing

34. Next Steps
● Intermediate topics:
– Classes and objects in Python
– Regular Expressions
– Exceptions etc
● Python on Appengine
● Python user group

35. Resources
● Official Python Docs tutorial
http://docs.python.org/2/tutorial/
● A byte of Python
http://www.swaroopch.com/notes/python/
● Think like a Computer Scientist
http://www.openbookproject.net/thinkcs/python/english2e/