Dictionaries

• Collection of unordered data.
• Key-Value pairs
  • You access the value by refering the key.

d = {
  "key1": "value1",
  "key2": "value2",
  "key3": "value3"
}

d["key1"]    # Call
d["key1"] = "value12"   # Set

d.items()
d.keys()
d.values()
len(d)    d.len()
d.update( { “key4” : “value4” } )

d2 = {}
  # Empty Dictionary
d2["key2_1"] = "value2_1"
d.union(d2)

print(d)
print(d["key2_1"])

del d["key1"] 
d.pop("key1") 
d.clear()

Loops

for k in d:
print("%s  : %s" %( k , d[k ]))

for k, val in d.items():
print("%s  : %s" %( k , val ))

for k in d.keys():
print("%s  : %s" %( k , val ))
    print(k, “\t”, d[k])

for value in d.values():
    print(value)

---

player = {
  "Name": "N00b_Master",
  "Character": "Malzahar",
  "Level": 25
}
len( player)   #  3
player[“Name”]   #  "N00b_Master"
player[“Weapon”]=  “Axe”
player[“Level] =+ 1
if “weapon” in player:
    del “weapon”   # Delete

---

phonebook = {
"John" : 938477566,
"Jack" : 938377264,
"Jill" : 947662781 }
for name, number in phonebook.items():
    print("Phone number of %s is %d" % (name, number))
del phonebook["John"]
if "John" not in phonebook:
    phonebook["John"] = 938478998

Compare Dictionaries

for k in d1.keys():
if k in d2: 
...
cmp(d1,d2) #  0 if equal

Indexation List

colours = { 1:"red",2:"blue",3:green}
colours[2] = "yellow"

Dictionary Merge

# How to merge two dictionaries

x = {'a': 1, 'b': 2}
y = {'b': 3, 'c': 4}

z = {**x, **y}

# z
# {'c': 4, 'a': 1, 'b': 3}




# In Python 2.x you could
# use this:
>>> z = dict(x, **y)
>>> z
{'a': 1, 'c': 4, 'b': 3}

# How to sort a Python dict by value
# (== get a representation sorted by value)

>>> xs = {'a': 4, 'b': 3, 'c': 2, 'd': 1}

>>> sorted(xs.items(), key=lambda x: x[1])
[('d', 1), ('c', 2), ('b', 3), ('a', 4)]

# Or:

>>> import operator
>>> sorted(xs.items(), key=operator.itemgetter(1))
[('d', 1), ('c', 2), ('b', 3), ('a', 4)]

# How to merge two dictionaries
# in Python 3.5+

>>> x = {'a': 1, 'b': 2}
>>> y = {'b': 3, 'c': 4}

>>> z = {**x, **y}

>>> z
{'c': 4, 'a': 1, 'b': 3}

# In Python 2.x you could
# use this:
>>> z = dict(x, **y)
>>> z
{'a': 1, 'c': 4, 'b': 3}

# In these examples, Python merges dictionary keys
# in the order listed in the expression, overwriting 
# duplicates from left to right.

# The get() method on dicts
# and its "default" argument

name_for_userid = {
    382: "Alice",
    590: "Bob",
    951: "Dilbert",
}

def greeting(userid):
    return "Hi %s!" % name_for_userid.get(userid, "there")

>>> greeting(382)
"Hi Alice!"

>>> greeting(333333)
"Hi there!"

food = { “Kiwi”:1, “Apple”:5}
print(“Strawberry” in food.keys())
food.update({ “Kiwi”:1, “Apple”:3}
foos.pop(“Kiwi”)

Dictionary methods

Get value

person = { "name" : 'John'}
print( person.get("name")) # returns the name
print( person.get("age", "Age unknown.")
  # provides alternative value. SAFE