Difference between revisions of "Object and Data Structure Basics"

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==Sets==
==Sets==
Sets are unordered collections of unique elements, meaning there can only be one representative of the same object
Sets are unordered collections of unique elements, meaning there can only be one representative of the same object
myset = set()
myset.add(1)
mylist = [1,1,1,2,2,3,3]
set(mylist) # will return only the unique values
output {1,2.3}

Revision as of 16:50, 4 January 2019

List

mylist= ['string', 1,2,3]
len(mylist) # get length of list
Result 3

Get part of a list (Slicing)

mylist[1:] gets from index one to the end
result 1,2,3

Concatenate list

another_list = [5,6]
newlist = mylist + anohter_list
result ['string', 1,2,3,5,6]

Add an item to the end of a list

newlist.append('hello')

Remove item from list

newlist.pop() # will pop last item
newlist.pop(0) # will pop index item 0

Sort and Reverse

newlist.sort() # sort list in place, which means you have to call newlist again to get the sorted results. you cannot do x = newlist.sort() becasue it will return nothing
numlist.reverse() # reverse in place

Dictionaries

Has key value pairs

mydict = {'key1':'value1', 'key2':'value2'}
mydict[key1]
out: value1
mydict2 = {'k1':123, 'k2':[0,1,2], 'k3':{'insidekey':100}}
mydict2['k2'][2]
mydict2['k3']['insidekey']

Add to dictionary

mydict2['k4'] = 300

List all keys in dictionary

mydict2.keys()

List all values in dictionary

dict2.values()

List both items and keys

dict2.items()

Tuples

Tuples are immutable

t=(1,2,3)
len(t)
t[0]
t.count(1) # will count the amount of time 1 appears
t.index(1) # will return the first index that 1 occurs

Sets

Sets are unordered collections of unique elements, meaning there can only be one representative of the same object

myset = set()
myset.add(1)
mylist = [1,1,1,2,2,3,3]
set(mylist) # will return only the unique values
output {1,2.3}