The document provides an introduction to Python programming concepts including functions, variables, data types, conditionals, loops, and data structures. It demonstrates a simple "Hello, World!" function and how to define, call, and assign the return value of functions. It also shows how to check variable types, use if/else conditional logic, iterate with for loops, and define a dictionary with nested data. The document uses examples and commentary to explain Python syntax and programming concepts in a beginner-friendly manner.

1. to...
NortHACKton

2. Why?

3. •Easy to learn
• Multi paradigm
• Extensive library
• Great community
• Fun!

4. http://python.org/download/
(for now use the 2.7 version)

5. “Hello, World!”
>>> print "Hello, World!"

6. “Hello, World!”
$ python
Python 2.6.1 (r261:67515, Jun 24 2010, 21:47:49)
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
Type "help", "copyright", "credits" or "license"
for more information.
>>> print "Hello, World!"
Hello, World!

7. “Hello, World!”
Start the Python interpreter
$ python
from the command line
Python 2.6.1 (r261:67515, Jun 24 2010, 21:47:49)
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
Type "help", "copyright", "credits" or "license"
for more information.
>>> print "Hello, World!"
Hello, World!

8. “Hello, World!”
$ python
Python 2.6.1 (r261:67515, Jun 24 2010, 21:47:49)
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
Type "help", "copyright", "credits" or "license"
for more information.
>>> print "Hello, World!"
Hello, World!
Generic information about the
Python interpreter.

9. “Hello, World!”
$ python
Python 2.6.1 (r261:67515, Jun 24 2010, 21:47:49)
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
Type "help", "copyright", "credits" or "license"
for more information.
>>> print "Hello, World!"
Hello, World!
You type this bit...

10. “Hello, World!”
$ python
Python 2.6.1 (r261:67515, Jun 24 2010, 21:47:49)
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
Type "help", "copyright", "credits" or "license"
for more information.
>>> print "Hello, World!"
Hello, World!
Python returns the result (you made that happen!)

11. “Hello, World!” function
def hello(name="World!"):
"""
Makes Python say hello.
:param name: who to greet
"""
return "Hello, %s" % name

12. “Hello, World!” function
Functions are named blocks of code that do stuff.
def hello(name="World!"):
"""
Makes Python say hello.
:param name: who to greet
"""
return "Hello, %s" % name

13. “Hello, World!” function
def = define
def hello(name="World!"):
"""
Makes Python say hello.
:param name: who to greet
"""
return "Hello, %s" % name

14. “Hello, World!” function
hello = name of function
def hello(name="World!"):
"""
Makes Python say hello.
:param name: who to greet
"""
return "Hello, %s" % name

15. “Hello, World!” function
an argument (input) into the function
def hello(name="World!"):
"""
Makes Python say hello.
:param name: who to greet
"""
return "Hello, %s" % name

16. “Hello, World!” function
a default value for the name arg
def hello(name="World!"):
"""
Makes Python say hello.
:param name: who to greet
"""
return "Hello, %s" % name

17. “Hello, World!” function
def hello(name="World!"):
"""
Makes Python say hello.
:param name: who to greet
"""
return "Hello, %s" % name
Whitespace (a 4 space indent) indicates scope

18. “Hello, World!” function
def hello(name="World!"):
"""
Makes Python say hello.
comments
& docs :param name: who to greet
"""
return "Hello, %s" % name

19. “Hello, World!” function
def hello(name="World!"):
"""
Makes Python say hello.
:param name: who to greet
"""
return "Hello, %s" % name
return = result

20. “Hello, World!” function
def hello(name="World!"):
"""
Makes Python say hello.
:param name: who to greet
"""
return "Hello, %s" % name
a string (use either ' or ")

21. “Hello, World!” function
def hello(name="World!"):
"""
Makes Python say hello.
:param name: who to greet
"""
return "Hello, %s" % name
string formatting

22. Call the function (note the brackets)
>>> hello()
'Hello, World!'
>>> hello("NortHACKton")
'Hello, NortHACKton'
>>> hello("Widget")
'Hello, Widget'

23. >>> hello() Here’s the result...
'Hello, World!'
>>> hello("NortHACKton")
'Hello, NortHACKton'
>>> hello("Widget")
'Hello, Widget'

24. >>> hello()
'Hello, World!'
>>> hello("NortHACKton")
'Hello, NortHACKton'
>>> hello("Widget")
'Hello, Widget'
Aha! Pass in arguments between the brackets...

25. HELP!
>>> dir()
['__builtins__', '__doc__',
'__name__', '__package__', 'hello']
>>> help(hello)
Help on function hello in module __main__:
hello(name='World!')
Makes Python say hello.
:param name: who to greet

26. HELP!
>>> dir() return the attributes of given scope
['__builtins__', '__doc__',
'__name__', '__package__', 'hello']
>>> help(hello) display help from docstring
Help on function hello in module __main__:
hello(name='World!')
Makes Python say hello.
:param name: who to greet

27. Assignment
>>> greeting = hello('NortHACKton!')
>>> greeting
'Hello, NortHACKton!'
>>> type(greeting)
<type 'str'>
>>> foo = 1
>>> type(foo)
<type 'int'>
>>> bar = 1.234
>>> type(bar)
<type 'float'>
>>> dir(greeting)
['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__', '__format__',
'__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__getslice__', '__gt__',
'__hash__', '__init__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__',
'__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__',
'__sizeof__', '__str__', '__subclasshook__', '_formatter_field_name_split',
'_formatter_parser', 'capitalize', 'center', 'count', 'decode', 'encode', 'endswith',
'expandtabs', 'find', 'format', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower',
'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'partition', 'replace',
'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines',
'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']

28. Assignment
>>> greeting = hello('NortHACKton!')
>>> greeting
greeting holds the return value
'Hello, NortHACKton!'
and it’s a string (of characters)!
>>> type(greeting)
<type 'str'>
>>> foo = 1
>>> type(foo)
<type 'int'>
>>> bar = 1.234
>>> type(bar)
<type 'float'>
>>> dir(greeting)
['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__', '__format__',
'__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__getslice__', '__gt__',
'__hash__', '__init__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__',
'__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__',
'__sizeof__', '__str__', '__subclasshook__', '_formatter_field_name_split',
'_formatter_parser', 'capitalize', 'center', 'count', 'decode', 'encode', 'endswith',
'expandtabs', 'find', 'format', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower',
'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'partition', 'replace',
'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines',
'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']

29. Assignment
>>> greeting = hello('NortHACKton!')
>>> greeting
'Hello, NortHACKton!'
>>> type(greeting)
foo holds the number 1
<type 'str'>
>>> foo = 1
>>> type(foo)
<type 'int'>
>>> bar = 1.234
and it’s an integer (whole number)!
>>> type(bar)
<type 'float'>
>>> dir(greeting)
['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__', '__format__',
'__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__getslice__', '__gt__',
'__hash__', '__init__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__',
'__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__',
'__sizeof__', '__str__', '__subclasshook__', '_formatter_field_name_split',
'_formatter_parser', 'capitalize', 'center', 'count', 'decode', 'encode', 'endswith',
'expandtabs', 'find', 'format', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower',
'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'partition', 'replace',
'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines',
'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']

30. Assignment
>>> greeting = hello('NortHACKton!')
>>> greeting
'Hello, NortHACKton!'
>>> type(greeting)
<type 'str'>
>>> foo = 1
>>> type(foo)
bar holds the number 1.234
<type 'int'>
>>> bar = 1.234
>>> type(bar)
<type 'float'>
>>> dir(greeting)
and it’s a float (’ing point number)!
['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__', '__format__',
'__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__getslice__', '__gt__',
'__hash__', '__init__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__',
'__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__',
'__sizeof__', '__str__', '__subclasshook__', '_formatter_field_name_split',
'_formatter_parser', 'capitalize', 'center', 'count', 'decode', 'encode', 'endswith',
'expandtabs', 'find', 'format', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower',
'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'partition', 'replace',
'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines',
'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']

31. Assignment
>>> greeting = hello('NortHACKton!')
>>> greeting
'Hello, NortHACKton!'
>>> type(greeting)
<type 'str'>
>>> foo = 1
>>> type(foo)
<type 'int'>
>>> bar = 1.234
>>> type(bar)
<type 'float'>
>>> dir(greeting) remember this..?
['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__', '__format__',
'__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__getslice__', '__gt__',
'__hash__', '__init__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__',
'__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__',
'__sizeof__', '__str__', '__subclasshook__', '_formatter_field_name_split',
'_formatter_parser', 'capitalize', 'center', 'count', 'decode', 'encode', 'endswith',
'expandtabs', 'find', 'format', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower',
'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'partition', 'replace',
'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines',
'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']

32. Assignment
>>> greeting = hello('NortHACKton!')
>>> greeting
'Hello, NortHACKton!'
>>> type(greeting)
<type 'str'>
>>> foo = 1
>>> type(foo)
<type 'int'>
>>> bar = 1.234
>>> type(bar)
<type 'float'>
>>> dir(greeting)
['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__', '__format__',
'__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__getslice__', '__gt__',
'__hash__', '__init__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__',
'__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__',
'__sizeof__', '__str__', '__subclasshook__', '_formatter_field_name_split',
'_formatter_parser', 'capitalize', 'center', 'count', 'decode', 'encode', 'endswith',
'expandtabs', 'find', 'format', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower',
'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'partition', 'replace',
'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines',
'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']
All of the attributes/functions of “greeting”

33. Program flow...
>>> world_is_flat = False
>>> if world_is_flat:
... print "The world is flat!"
... else:
... print "The world is round"
...
The world is round

34. Program flow...
>>> world_is_flat = False
>>> if world_is_flat: “if” tests for truth
... print "The world is flat!"
... else: “else” if “if” evaluates to false
... print "The world is round"
...
The world is round
The result of this logic...

35. Program flow...
>>> world_is_flat = False
>>> if world_is_flat:
... print "The world is flat!"
... else:
... print "The world is round"
...
The world is round
NB: there is NO switch in Python. Use elif for
further clauses in the logic.

36. Loops
>>> for number in range(10):
... print number
...
Basically, for each “something” in a
group of “somethings” do something
(for each number in a group of
numbers print the number)

37. Loops
>>> for number in range(10):
... print number
...
0
1
2
3 Like many programming languages,
4 Python starts counting from 0 (zero)
5
6
7
8
9
There’s also while

38. Data structures
>>> my_dictionary = { curly brackets!
... 'key': 'value',
... 1: 2, dict = key/value store
... 'branch': {
... 'leaf': 'node' (think phone book)
... }
... }
>>> my_dictionary['key'] get the value from the dict
'value'
>>> my_dictionary[1]
2
>>> my_dictionary['branch']['leaf']
'node'
>>> my_dictionary
{1: 2, 'branch': {'leaf': 'node'}, 'key': 'value'}
Why not try dir(my_dictionary)and play.?

39. Data structures
>>> shopping = ['eggs', 'ham', 'spam', 'parrot'] a list
>>> len(shopping)
4 square brackets!
>>> shopping
['eggs', 'ham', 'spam', 'parrot'] lists remain in order
>>> shopping[0]
'eggs'
>>> shopping[3] get a specific item by position
'parrot'
>>> shopping[4]
Traceback (most recent call last): start counting from
File "<stdin>", line 1, in <module>
IndexError: list index out of range zero (remember?)
>>> shopping[1:]
['ham', 'spam', 'parrot']
>>> shopping[:1]
['eggs']
>>> shopping[:-1]
slicing
['eggs', 'ham', 'spam']
>>> shopping[-1:]
['parrot']

41. Modules
import antigravity
from antigravity import stasisfield
stasisfield.generate()

42. OOP(s)

43. In a nutshell
(there’s much more to it than this)
Classes define sorts of things
Objects are instances of classes

44. Cow = class
Buttercup = object (an
instance of cow)

45. In a nutshell (part 2)
(there’s still much more to it than this)
Methods do things (they’re functions)
Attributes define, er, attributes...

46. Moo! Buttercup.moo()
Buttercup.breed = “friesian”

47. A very simple view...
Nouns = Classes
Proper Nouns = Objects
Verbs = Methods
Adjectives = Attributes
er, sort of... I’m making this up as I go along... :-)

48. class Cow(object):
"""
A pythonic cow
"""
def __init__(self, name="Cow", breed=None):
"""
Called when the class is instantiated
"""
self.name = name
self.breed = breed
def moo(self, message="MOO!"):
"""
A bovine hello world!
"""
return "%s says, %s" % (self.name, message)

49. Indicates we’re defining a new class...
class Cow(object):
"""
A pythonic cow
"""
def __init__(self, name="Cow", breed=None):
"""
Called when the class is instantiated
"""
self.name = name
self.breed = breed
def moo(self, message="MOO!"):
"""
A bovine hello world!
"""
return "%s says, %s" % (self.name, message)

50. ... that we’re calling “Cow”...
class Cow(object):
"""
A pythonic cow
"""
def __init__(self, name="Cow", breed=None):
"""
Called when the class is instantiated
"""
self.name = name
self.breed = breed
def moo(self, message="MOO!"):
"""
A bovine hello world!
"""
return "%s says, %s" % (self.name, message)

51. ... that inherits attributes/behaviour
from the“object” class.
class Cow(object):
"""
A pythonic cow
"""
def __init__(self, name="Cow", breed=None):
"""
Called when the class is instantiated
"""
self.name = name
self.breed = breed
def moo(self, message="MOO!"):
"""
A bovine hello world!
"""
return "%s says, %s" % (self.name, message)

52. class Cow(object): A docstring that explains
"""
A pythonic cow what this class represents
"""
def __init__(self, name="Cow", breed=None):
"""
Called when the class is instantiated
"""
self.name = name
self.breed = breed
def moo(self, message="MOO!"):
"""
A bovine hello world!
"""
return "%s says, %s" % (self.name, message)

53. class Cow(object):
"""
A pythonic cow
"""
def __init__(self, name="Cow", breed=None):
"""
A special Called when the class is instantiated
"""
method self.name = name
self.breed = breed
called when
a new def moo(self, message="MOO!"):
"""
object is A bovine hello world!
"""
created return "%s says, %s" % (self.name, message)
with this
class

54. class Cow(object):
"""
A pythonic cow “self” refers to the new
"""
object (e.g. Buttercup)
def __init__(self, name="Cow", breed=None):
"""
Called when the class is instantiated
"""
self.name = name
self.breed = breed
def moo(self, message="MOO!"):
"""
A bovine hello world!
"""
return "%s says, %s" % (self.name, message)

55. class Cow(object):
"""
A pythonic cow
"""
def __init__(self, name="Cow", breed=None):
"""
Called when the class is instantiated
"""
self.name = name self.name and self.breed
self.breed = breed
are attributes of the
def moo(self, message="MOO!"): instantiated object
"""
A bovine hello world! (Buttercup)
"""
return "%s says, %s" % (self.name, message)

56. class Cow(object):
"""
A pythonic cow
"""
def __init__(self, name="Cow", breed=None):
"""
Called when the class is instantiated
"""
self.name = name
self.breed = breed
def moo(self, message="MOO!"):
"""
A bovine hello world!
A method """
return "%s says, %s" % (self.name, message)
makes the
object do
something

57. >>> from example import Cow
>>> buttercup = cow("Buttercup", "friesian")
>>> buttercup.name
'Buttercup'
>>> buttercup.breed
'friesian'
>>> buttercup.moo()
'Buttercup says, MOO!'

58. http://docs.python.org/tutorial/introduction.html

59. and now for something completely different...

60. Your task:
Create a Parrot class. It must be able to squawk, flap and,
ahem, become deceased. If the parrot is deceased then
calling squawk and flap return the message “This is an ex-
parrot”. We should be able to indicate the parrot’s breed
and give it a name. Use your imagination! HAVE FUN!

61. Show and tell...

62. End (the)
http://python.org/