Python Fundamentals (Sets & Dictionaries)

Here are notes in regards to how Python handles sets and dictionaries as well as how to get built in functions to work utilizing the help section.

List Operations

• Concatenate -- [1,2] + [3,4] = [1,2,3,4]
• Append -- list.append()
• Extend -- list.extend([])
• Reverse -- list.reverse()
• Pop -- list.pop()
• Insert -- list.insert(index, item)
• Delete -- del list[index]

Sets: unordered collection of unique objects

List to set:
>>> setA = set([1,2,3,3,2])
>>>
>>> setA
set([1, 2, 3])
>>>
>>> setB = set([3,4,5])
>>>
>>> setB
set([3, 4, 5])
>>>

Set operations: Union
>>> setA|setB
set([1, 2, 3, 4, 5])
>>>

Set operations: Intersection
>>> setA&setB
set([3])

Set operations: Difference
>>> setA-setB
set([1, 2])
>>>
>>> setB-setA
set([4, 5])

Dictionaries: unordered key-value pairs which values can change.  Keys are unique and immutable objects.

• dict = {} (empty dictionary)
• dict['name'] = 'bob'
• dict(name='bob', age='33')
• dict = { 'name' : 'bob', 'age' : 33 }

How to test for alias keys in dictionary.

>>> myInfo

{'hobby': 'hacking', 'age': 33, 'name': 'bob'}

>>> myInfo.has_key('hobby')

True

>>>

>>> myInfo.has_key('hobbies')

False

>>>

>>> 'name' in myInfo

True

>>>

Get a list of keys:

>>> myInfo.keys()

['hobby', 'age', 'name']

>>>

Get a list of values:

>>> myInfo.values()

['hacking', 33, 'chris']

>>>

Get a tuple of items:

>>> myInfo.items()

[('hobby', 'hacking'), ('age', 33), ('name', 'chris')]

>>>

Get a particular item:

>>> myInfo.get('age')

33

How to get built in functions for a particular object.

>>> dir(myInfo)

['__class__', '__cmp__', '__contains__', '__delattr__', '__delitem__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__init__', '__iter__', '__le__', '__len__', '__lt__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__setitem__', '__sizeof__', '__str__', '__subclasshook__', 'clear', 'copy', 'fromkeys', 'get', 'has_key', 'items', 'iteritems', 'iterkeys', 'itervalues', 'keys', 'pop', 'popitem', 'setdefault', 'update', 'values']

Getting help on methods.

>>> help(myInfo.__delattr__)