d = {}

d['a'] = 1

d['b'] = 2

print(d)

{'a': 1, 'b': 2}

print(d['a'])

1

d['c'] = 3

d['a'] = 100

print(d)

{'a': 100, 'b': 2, 'c': 3}

del d['b']

print(d)

{'a': 100, 'c': 3}

len(d)

2

d.get('a')

100

d.get('z', 'not found')

'not found'

'c' in d

True

'z' in d

False

d.keys()

dict_keys(['a', 'c'])

d.values()

dict_values([100, 3])

d.items()

dict_items([('a', 100), ('c', 3)])

for key in d: print(key)

a
c

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

100
3

for k, v in d.items(): print(k, v)

a 100
c 3

dict1 = {'x': 1, 'y': 2}

dict2 = {'y': 3, 'z': 4}

dict1.update(dict2)

print(dict1)

{'x': 1, 'y': 3, 'z': 4}

dict3 = dict1.copy()

print(dict3)

{'x': 1, 'y': 3, 'z': 4}

dict3.clear()

print(dict3)

{}

dict4 = dict(a=1, b=2)

print(dict4)

{'a': 1, 'b': 2}

dict5 = {i: i**2 for i in range(5)}

print(dict5)

{0: 0, 1: 1, 2: 4, 3: 9, 4: 16}

tuple_key = (1, 2)

d[tuple_key] = 'tuple as key'

print(d)

{'a': 100, 'c': 3, (1, 2): 'tuple as key'}

try: print(d['missing'])
except KeyError: print('KeyError')

KeyError

default = d.setdefault('new', 999)

print(d)

{'a': 100, 'c': 3, (1, 2): 'tuple as key', 'new': 999}

print(default)

999

d.pop('new')

999

print(d)

{'a': 100, 'c': 3, (1, 2): 'tuple as key'}

d.popitem()

((1, 2), 'tuple as key')

print(d)

{'a': 100, 'c': 3}

from collections import defaultdict

dd = defaultdict(int)

dd['a'] += 1

print(dd)

defaultdict(<class 'int'>, {'a': 1})

from collections import OrderedDict

od = OrderedDict()

od['a'] = 1

od['b'] = 2

print(od)

OrderedDict({'a': 1, 'b': 2})

od.move_to_end('a')

print(od)

OrderedDict({'b': 2, 'a': 1})

od.popitem(last=False)

('b', 2)

print(od)

OrderedDict({'a': 1})

d = dict([('x', 10), ('y', 20)])

print(d)

{'x': 10, 'y': 20}

zipped = zip(['a', 'b'], [1, 2])

d = dict(zipped)

print(d)

{'a': 1, 'b': 2}

d = {chr(65+i): i for i in range(10)}

print(d)

{'A': 0, 'B': 1, 'C': 2, 'D': 3, 'E': 4, 'F': 5, 'G': 6, 'H': 7, 'I': 8, 'J': 9}

d = {x: x+1 for x in range(10) if x % 2 == 0}

print(d)

{0: 1, 2: 3, 4: 5, 6: 7, 8: 9}

hash('abc')

-6797330088782940123

hash(123)

123

hash((1,2))

-3550055125485641917

d = {'a': {'nested': 1}}

print(d['a']['nested'])

1

d['a']['nested'] += 1

print(d)

{'a': {'nested': 2}}

d = {i: chr(65+i) for i in range(5)}

for k in sorted(d): print(k, d[k])

0 A
1 B
2 C
3 D
4 E

inverse = {v: k for k, v in d.items()}

print(inverse)

{'A': 0, 'B': 1, 'C': 2, 'D': 3, 'E': 4}

import json

json_str = json.dumps(d)

print(json_str)

{"0": "A", "1": "B", "2": "C", "3": "D", "4": "E"}