5. PLEAC Julia: Dictionaries¶

PLEAC = Language Examples Alike Cookbook PLEAC examples are drawn from the "Perl Cookbook" by Tom Christiansen & Nathan Torkington, published by O'Reilly. They provide a nice range of examples oriented toward data munging, the type of work I tend to want to do first when learning a new language.

The Julia examples below are principally translations from the Python version

A Caution¶

I'm learning as I go, so the code below probably doesn't represent best practice. Your suggestions are welcome! Please file an issue or make a pull request to the github repo.

The examples are not complete. Missing items are generally noted in comments.

PLEAC 5.0: Introduction¶

In [1]:

#Dict of Any
age = {"Nat"=> 24,       "Jules"=> 24,       "Josh"=> 17}

Out[1]:

{"Jules"=>24,"Josh"=>17,"Nat"=>24}

In [2]:

#typed Dict-- the type will be inferred
age = ["Nat"=> 24,       "Jules"=> 24,       "Josh"=> 17]

Out[2]:

["Jules"=>24,"Josh"=>17,"Nat"=>24]

In [3]:

age=Dict()
age["Nat"] = 24
age["Jules"] = 25
age["Josh"] = 17

Out[3]:

In [4]:

#in Julia, keys can be Symbols
food_color = [:Apple => "red",
              :Banana=> "yellow",
              :Lemon => "yellow",
              :Carrot=> "orange"
             ]

Out[4]:

[:Apple=>"red",:Carrot=>"orange",:Lemon=>"yellow",:Banana=>"yellow"]

PLEAC 5.1: Adding an element to a Dict¶

In [5]:

# food_color defined per the introduction
food_color[:Raspberry] = "pink"
print( "Known foods:" )
for food in food_color
    print( food )
end

Known foods:(:Apple,"red")(:Raspberry,"pink")(:Carrot,"orange")(:Lemon,"yellow")(:Banana,"yellow")

PLEAC 5.2: Testing for the presence of a key in a Dict¶

does dict have a value for key?

In [6]:

key = "Joe"
haskey(age,key)

Out[6]:

false

In [7]:

key="Nat"
haskey(age,key)

Out[7]:

true

In [8]:

# food_color per the introduction
for name in (:Banana, :Martini)
    if name in keys(food_color)
        println("$name is a food.")
    else
        println( "$name is a drink.")
    end
end

Banana is a food.
Martini is a drink.

In [9]:

age = Dict()
age["Toddler"] = 3
age["Unborn"] = 0
age["Phantasm"] = None

Out[9]:

None

In [10]:

thing="Toddler"
thing ==Nothing

Out[10]:

false

In [11]:

for thing in ("Toddler", "Unborn", "Phantasm", "Relic")
    print("\n$thing: ")
    if haskey(age, thing)
        print( "Exists ")
        if age[thing] != None
            print(" Defined")
        end
        if age[thing]==true
            print( " true")
        end
    end
    #println()
end

Toddler: Exists  Defined
Unborn: Exists  Defined
Phantasm: Exists 
Relic:

In [11]:

#SKIP
# Get file sizes for the requested filenames
"""
import fileinput, os
size = {}
for line in fileinput.input():
    filename = line.rstrip()
    if filename in size:
        continue
    size[filename] = os.path.getsize(filename)
""";

PLEAC 5.3: Delete from a Dict¶

remove key and value from dict

In [12]:

delete!(age, "Nat")

Out[12]:

{"Toddler"=>3,"Unborn"=>0,"Phantasm"=>None}

In [13]:

foodstr = {"carrot"=>"orange", "lemon"=>"yellow", 
           "apple"=>"green", "banana"=>"yellow"}

Out[13]:

{"apple"=>"green","carrot"=>"orange","lemon"=>"yellow","banana"=>"yellow"}

In [14]:

function print_foods()
    foods = keys(foodstr)
    println("Keys: $(join(foods,' '))")
    println("Values: $( join(values(foodstr),' ') )")
end

Out[14]:

print_foods (generic function with 1 method)

In [15]:

println("Initially:")
print_foods()

Initially:
Keys: apple carrot lemon banana
Values: green orange yellow yellow

In [16]:

println("\nWith banana set to nothing")
foodstr["banana"]=None  # works for Dict{String,Any}.  for typed Dict, would need a Union(T,None)
print_foods()

With banana set to nothing
Keys: apple carrot lemon banana
Values: green orange yellow None

In [17]:

println("\nWith banana deleted")
delete!( foodstr, "banana" )
print_foods()

With banana deleted
Keys: apple carrot lemon
Values: green orange yellow

In [18]:

for key in ["Banana", "apple", "Cabbage"] 
    delete!(foodstr,key)  #delete!() does not mind getting non-existant keys
end
foodstr

Out[18]:

{"carrot"=>"orange","lemon"=>"yellow"}

PLEAC 5.4: Traversing a Dict¶

In [19]:

foodstr = {"carrot"=>"orange", "lemon"=>"yellow", 
           "apple"=>"green", "banana"=>"yellow"}

Out[19]:

{"apple"=>"green","carrot"=>"orange","lemon"=>"yellow","banana"=>"yellow"}

In [20]:

for k in keys(foodstr)
  println("$k $(foodstr[k])")
end

apple green
carrot orange
lemon yellow
banana yellow

In [21]:

for (k,v) in collect(foodstr)
   println("$k $v")
end

apple green
carrot orange
lemon yellow
banana yellow

In [22]:

for (k,v) in sort(collect(foodstr))
   println("$k $v")
end

apple green
banana yellow
carrot orange
lemon yellow

In [23]:

text = """From: Jo
To: Jim
From: Jane
"""
infile = IOBuffer(text)

Out[23]:

IOBuffer([0x46,0x72,0x6f,0x6d,0x3a,0x20,0x4a,0x6f,0x0a,0x54  …  0x72,0x6f,0x6d,0x3a,0x20,0x4a,0x61,0x6e,0x65,0x0a],true,false,true,false,28,9223372036854775807,1)

In [24]:

counts = Dict()
for line in readlines(infile)
    if line[1:6]=="From: "
        name=chomp(line[7:end])
        counts[name] = get(counts,name,0)+1
    end
end

In [25]:

for (name, count) in collect(counts)
    println("$name $count")
end

Jo 1
Jane 1

PLEAC 5.5: Printing a Dict¶

In [26]:

for (name, count) in collect(counts)
    println("$name => $count")
end

Jo => 1
Jane => 1

In [27]:

join(["$k => $v" for (k,v) in collect(counts)],'\n')

Out[27]:

"Jo => 1\nJane => 1"

In [28]:

print(counts)

{"Jo"=>1,"Jane"=>1}

In [29]:

show(counts)

{"Jo"=>1,"Jane"=>1}

PLEAC 5.6: Retrieving from a Dict in Insertion Order¶

In [30]:

#install OrderedCollections.jl ?

In [31]:

# @@INCOMPLETE@

PLEAC 5.7: Dicts with multiple values per key¶

In [36]:

LOAD_PATH

Out[36]:

2-element Array{Union(ASCIIString,UTF8String),1}:
 "C:\\Temp\\julia-rc4\\local\\share\\julia\\site\\v0.2"
 "C:\\Temp\\julia-rc4\\share\\julia\\site\\v0.2"

In [32]:

multfood = ["carrot"=>["orange","green"], 
            "lemon"=>["yellow","brown"], 
            "apple"=>["green","red"], 
            "banana"=>["yellow","brown"] 
            ]

Out[32]:

["apple"=>["green","red"],"carrot"=>["orange","green"],"lemon"=>["yellow","brown"],"banana"=>["yellow","brown"]]

PLEAC 5.8: Inverting a Dict¶

In [33]:

{v=>k for (k,v) in [(1,2),(3,4)]}

Out[33]:

{4=>3,2=>1}

In [34]:

surname = {"Mickey"=>"Mantle", "Babe"=>"Ruth"}

Out[34]:

{"Babe"=>"Ruth","Mickey"=>"Mantle"}

In [35]:

first_name = {v=>k for (k,v) in collect(surname)}

Out[35]:

{"Ruth"=>"Babe","Mantle"=>"Mickey"}

In [36]:

print(first_name["Mantle"])

Mickey

In [41]:

color_dict = {"Apple"=>  "red",
              "Banana"=> "yellow",
              "Lemon"=>  "yellow",
              "Carrot"=> "orange",
             }

Out[41]:

{"Banana"=>"yellow","Lemon"=>"yellow","Carrot"=>"orange","Apple"=>"red"}

In [42]:

food_dict = {v=>k for (k,v) in collect(color_dict)}

Out[42]:

{"orange"=>"Carrot","red"=>"Apple","yellow"=>"Lemon"}

In [46]:

given = "Apple"
if given in keys(color_dict)
    println("$given is a food with color $(color_dict[given])")
elseif given in keys(food_dict)
    println("$(color_dict[given]) is a food with color $given ")
end

Apple is a food with color red

In [50]:

food_color

Out[50]:

[:Apple=>"red",:Raspberry=>"pink",:Carrot=>"orange",:Lemon=>"yellow",:Banana=>"yellow"]

In [53]:

foods_with_color=Dict()
for (food,color) in color_dict
  if haskey(foods_with_color,color)
    push!(foods_with_color[color], food)
  else
    foods_with_color[color] = [food]
  end
end
foods_with_color

Out[53]:

{"orange"=>["Carrot"],"red"=>["Apple"],"yellow"=>["Banana","Lemon"]}

In [57]:

println( join(foods_with_color["yellow"], ' '), " were yellow foods.")

Banana Lemon were yellow foods.

PLEAC 5.9: Sorting a Dictionary¶

In [64]:

for (f,c) in sort(collect(color_dict))
    println(f," is ",c)
end

Apple is red
Banana is yellow
Carrot is orange
Lemon is yellow

In [73]:

function compare_length(x,y)
    return length(string(x))<length(string(y))
end

Out[73]:

compare_length (generic function with 1 method)

In [78]:

for k in sort(collect(keys(color_dict)),lt=compare_length)
    println(k," is ",color_dict[k])
end

Lemon is yellow
Apple is red
Banana is yellow
Carrot is orange

In [76]:

collect(keys(color_dict))

Out[76]:

4-element Array{Any,1}:
 "Banana"
 "Lemon" 
 "Carrot"
 "Apple"

In [79]:

for k in sort(collect(keys(color_dict)), by=length, rev=true)
    println(k," is ",color_dict[k])
end

Banana is yellow
Carrot is orange
Lemon is yellow
Apple is red

PLEAC 5.10: Merging Dictionaries¶

In [89]:

d1 = Dict((1,2,3),(4,5,6))

Out[89]:

[2=>5,3=>6,1=>4]

In [90]:

d2 = Dict((1,4),(7,8))

Out[90]:

[4=>8,1=>7]

In [92]:

merge(d1,d2)  #where a key is shared between d1 and d2, the result keeps the key-value pair from d2

Out[92]:

[4=>8,2=>5,3=>6,1=>7]

In [93]:

# food_color as per section 5.8
drink_color = {"Galliano"=> "yellow",
               "Mai Tai"=> "blue"}

Out[93]:

{"Galliano"=>"yellow","Mai Tai"=>"blue"}

In [95]:

ingested_color = copy(drink_color)

Out[95]:

{"Galliano"=>"yellow","Mai Tai"=>"blue"}

In [96]:

merge!(ingested_color, food_color)

Out[96]:

{:Apple=>"red",:Raspberry=>"pink",:Carrot=>"orange","Galliano"=>"yellow","Mai Tai"=>"blue",:Lemon=>"yellow",:Banana=>"yellow"}

PLEAC 5.11: Finding Common or Different Keys in Two Dictionaries¶

In [98]:

common = [k for k in intersect(keys(d1),keys(d2))]

Out[98]:

1-element Array{Any,1}:
 1

In [101]:

this_not_that = [(k,d1[k]) for k in setdiff(keys(d1),keys(d2))]

Out[101]:

2-element Array{(Any,Any),1}:
 (2,5)
 (3,6)

In [102]:

# citrus_color is a dict mapping citrus food name to its color.
citrus_color = {"Lemon"=>  "yellow",
                "Orange"=> "orange",
                "Lime"=>   "green"}

Out[102]:

{"Lime"=>"green","Lemon"=>"yellow","Orange"=>"orange"}

In [105]:

# build up a list of non-citrus foods
non_citrus = [ (k,color_dict[k]) for k in setdiff(keys(color_dict),keys(citrus_color)) ]

Out[105]:

3-element Array{(Any,Any),1}:
 ("Banana","yellow")
 ("Carrot","orange")
 ("Apple","red")

PLEAC 5.12: Dictionary references¶

In [106]:

# @@INCOMPLETE@

PLEAC 5.13: Presizing a dictionary¶

In [107]:

mydict = Dict()
sizehint(mydict, 100)

Out[107]:

Dict{Any,Any}()

PLEAC 5.14: Finding the most common anything¶

In [114]:

myarray = [1,2,4,5,3,4,7,8,4,3,2,5,5,7,8]
count = Dict()
for element in myarray
    count[element] = get(count,element, 0) + 1
end
count

Out[114]:

{5=>3,4=>3,7=>2,2=>2,8=>2,3=>2,1=>1}

In [110]:

for element in myarray
    print(element)
end

124534784325578

PLEAC 5.15: Representing Relationships Between Data¶

In [116]:

father = {"Cain"=> "Adam",
          "Abel"=> "Adam",
          "Seth"=> "Adam",
          "Enoch"=> "Cain",
          "Irad"=> "Enoch",
          "Mehujael"=> "Irad",
          "Methusael"=> "Mehujael",
          "Lamech"=> "Methusael",
          "Jabal"=> "Lamech",
          "Tubalcain"=> "Lamech",
          "Enos"=> "Seth",
         }

Out[116]:

{"Methusael"=>"Mehujael","Irad"=>"Enoch","Mehujael"=>"Irad","Lamech"=>"Methusael","Enos"=>"Seth","Tubalcain"=>"Lamech","Abel"=>"Adam","Enoch"=>"Cain","Jabal"=>"Lamech","Seth"=>"Adam","Cain"=>"Adam"}

In [117]:

#SKIP fileinput stuff
# @@INCOMPLETE@

In [127]:

children=Dict()
for (k, v) in collect(father)
    if haskey(children,v)
        push!(children[v],k)
    else
        children[v]=[k]
    end
end
children

Out[127]:

{"Methusael"=>["Lamech"],"Irad"=>["Mehujael"],"Adam"=>["Abel","Seth","Cain"],"Mehujael"=>["Methusael"],"Lamech"=>["Tubalcain","Jabal"],"Enoch"=>["Irad"],"Seth"=>["Enos"],"Cain"=>["Enoch"]}

In [118]:

dd=Dict()

Out[118]:

Dict{Any,Any}()

In [128]:

# RE on filenames skipped
# Will not implement
# @@INCOMPLETE@

PLEAC 5.16: Program dutree¶

In [129]:

# Will not implment
# @@INCOMPLETE@

In [38]:

;ipython nbconvert 5_pleac_dictionaries.ipynb

[NbConvertApp] Using existing profile dir: u'C:\\Users\\keithc\\.ipython\\profile_default'
[NbConvertApp] Converting notebook 5_pleac_dictionaries.ipynb to html
[NbConvertApp] Support files will be in 5_pleac_dictionaries_files\
[NbConvertApp] Loaded template html_full.tpl
[NbConvertApp] Writing 268953 bytes to 5_pleac_dictionaries.html

In [ ]: