Data structures

    • collection of elements with defined order

    • flexible: elements can be added, removed, replaced: d.append('B')

    • indexed elements, zero-based: d[0]


    • like lists that cannot be changed

    • ordered (indexed)

    • constant: elements cannot be changed


    • collection of unique elements (duplicated values are removed)

    • no particular order (no index)

    • flexible: elements can be added, removed, replaced: d.add('B')

    • logical operations between sets: d1.union(d2)

    • loop / test: if 'B' in d:

    • a set is like a dictionary with no values

    • like sets, but with the possibility to add data to each element: d['Mike']=('Berlin',1983)

    • no particular order (no index)

    • elements are unique (key-words)

    • flexible: elements and data can be added, removed, replaced


d={} is an empty dictionary

d={'A'} is a set

d=set() is an empty set

d=() is an empty tuple

d=[] is en empty list

It's a bit confusing.. to check the data type use:

>>> type(d)

<type 'list'>

Convert data type

# check type

>>> mylist = ['A', 'B', 'A']

>>> type(mylist)

<type 'list'>

# convert list to set

>>> myset=set(mylist)

>>> myset

set(['A', 'B'])

>>> type(myset)

<type 'set'>