Dictionary in Python (3)

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*Memo:

• My post explains a dictionary (1).
• My post explains a dictionary (2) and the dictionary with keying and copy.
• My post explains dictionary functions (2).

items(), keys() and values() can be used with a dictionary as shown below:

*Memo:

• items() can get zero or more keys and values from the dictionary:
  • It has no arguments.
• keys() can get zero or more keys from the dictionary:
  • It has no arguments.
• values() can get zero or more values from the dictionary:
  • It has no arguments.

v = {'name':'John', 'age':36}

print(v.keys())
# dict_keys(['name', 'age'])

print(v.values())
# dict_values(['John', 36])

print(v.items())
# dict_items([('name', 'John'), ('age', 36)])

v = {'person1':{'name':'John', 'age':36},
     'person2':{'name':'Anna', 'age':24}}

print(v.keys())
# dict_keys(['person1', 'person2'])

print(v.values())
# dict_values([{'name': 'John', 'age': 36},
#              {'name': 'Anna', 'age': 24}])

print(v.items())
# dict_items([('person1', {'name': 'John', 'age': 36}),
#             ('person2', {'name': 'Anna', 'age': 24})])

print(v['person2'].keys())
# dict_keys(['name', 'age'])

print(v['person2'].values())
# dict_values(['Anna', 24])

print(v['person2'].items())
# dict_items([('name', 'Anna'), ('age', 24)])

By default, the one or more keys of a dictionary are used with an iterable unpacking as shown below:

v1 = {'name':'John', 'age':36}

v2, v3 = v1
v2, v3 = v1.keys()

print(v2, v3)
# name age

v1 = {'name':'John', 'age':36}

v2, v3 = v1..values()

print(v2, v3)
# John 36

v1 = {'name':'John', 'age':36}

v2, v3 = v1.items()

print(v2, v3)
# ('name', 'John') ('age', 36)

v1 = {'person1':{'name':'John', 'age':36},
      'person2':{'name':'Anna', 'age':24}}

v2, v3 = v1
v2, v3 = v1.keys()

print(v2, v3)
# person1 person2

v1 = {'person1':{'name':'John', 'age':36},
      'person2':{'name':'Anna', 'age':24}}

v2, v3 = v1.values()

print(v2, v3)
# {'name': 'John', 'age': 36} {'name': 'Tom', 'age': 24}

v1 = {'person1':{'name':'John', 'age':36},
      'person2':{'name':'Anna', 'age':24}}

v2, v3 = v1.items()

print(v2) # ('person1', {'name': 'John', 'age': 36})
print(v3) # ('person2', {'name': 'Anna', 'age': 24})

v1 = {'person1':{'name':'John', 'age':36},
      'person2':{'name':'Anna', 'age':24}}

v2, v3 = v1['person2']
v2, v3 = v1['person2'].keys()
print(v2, v3)
# name age

v2, v3 = v1['person2'].values()
print(v2, v3)
# Anna 24

v2, v3 = v1['person2'].items()
print(v2, v3)
# ('name', 'Anna') ('age', 24)

v1 = {'person1':{'name':'John', 'age':36},
      'person2':{'name':'Anna', 'age':24}}.values()

v2, v3 = v1

print(v2, v3)
# {'name': 'John', 'age': 36} {'name': 'Anna', 'age': 24}

v1 = {'person1':{'name':'John', 'age':36},
      'person2':{'name':'Anna', 'age':24}}.items()

v2, v3 = v1

print(v2) # ('person1', {'name': 'John', 'age': 36})
print(v3) # ('person2', {'name': 'Anna', 'age': 24})

sorted() can convert a dictionary to the list which has the zero or more keys and/or values of the dictionary, then sort the list as shown below:

*Memo:

• The 1st argument is iterable(Required-Type:Iterable):
  • Don't use iterable=.
• The 2nd argument is key(Optional-Default:None-Type:Callable or NoneType).
• The 3rd argument is reverse(Optional-Default:False) to reverse the list.
• By default, the list which has the zero or more keys of a dictionary is used.
• sorted() creates a copy:
  • Be careful, sorted() does shallow copy instead of deep copy as my issue.

v = {'name':'John', 'age':36}

print(sorted(v))
print(sorted(v, key=None, reverse=False))
print(sorted(v.keys()))
# ['age', 'name']

print(sorted(v.values(), key=lambda key: str(key)))
# [36, 'John']

print(sorted(v.items()))
# [('age', 36), ('name', 'John')]

print(sorted(v, reverse=True))
print(sorted(v.keys(), reverse=True))
# ['name', 'age']

print(sorted(v.values(), key=lambda key: str(key), reverse=True))
# ['John', 36]

print(sorted(v.items(), reverse=True))
# [('name', 'John'), ('age', 36)]

v = {'person1':{'name':'John', 'age':36},
     'person2':{'name':'Anna', 'age':24}}

print(sorted(v))
print(sorted(v.keys()))
# ['person1', 'person2']

print(sorted(v.values(), key=lambda key: str(key)))
# [{'name': 'Anna', 'age': 24},
#  {'name': 'John', 'age': 36}]

print(sorted(v.items()))
# [('person1', {'name': 'John', 'age': 36}),
#  ('person2', {'name': 'Anna', 'age': 24})]

print(sorted(v, reverse=True))
print(sorted(v.keys(), reverse=True))
# ['person2', 'person1']

print(sorted(v.values(), key=lambda key: str(key), reverse=True))
# [{'name': 'John', 'age': 36},
#  {'name': 'Anna', 'age': 24}]

print(sorted(v.items(), reverse=True))
# [('person2', {'name': 'Anna', 'age': 24}),
#  ('person1', {'name': 'John', 'age': 36})]

print(sorted(v['person2']))
print(sorted(v['person2'].keys()))
# ['age', 'name']

print(sorted(v['person2'].values(), key=lambda key: str(key)))
# [24, 'Anna']

print(sorted(v['person2'].items()))
# [('age', 24), ('name', 'Anna')]

print(sorted(v['person2'], reverse=True))
print(sorted(v['person2'].keys(), reverse=True))
# ['name', 'age']

print(sorted(v['person2'].values(), key=lambda key: str(key), reverse=True))
# ['Anna', 24]

print(sorted(v['person2'].items(), reverse=True))
# [('name', 'Anna'), ('age', 24)]

reversed() can return the iterator which has the reversed zero or more keys and/or values of a dictionary, then the iterator is converted to a list with list() as shown below:

*Memo:

• The 1st argument is seq(Required:Type-Sequence):
  • Don't use seq=.
• By default, the list which has the zero or more keys of a dictionary is used.

v = {'name':'John', 'age':36}

print(reversed(v))
# <dict_reversekeyiterator object at 0x000001F3B9E51530>

print(list(reversed(v)))
print(list(reversed(v.keys())))
# ['age', 'name']

print(list(reversed(v.values())))
# [36, 'John']

print(list(reversed(v.items())))
# [('age', 36), ('name', 'John')]

v = {'person1':{'name':'John', 'age':36},
     'person2':{'name':'Anna', 'age':24}}

print(list(reversed(v)))
print(list(reversed(v.keys())))
# ['person2', 'person1']

print(list(reversed(v.values())))
# [{'name': 'Anna', 'age': 24},
#  {'name': 'John', 'age': 36}]

print(list(reversed(v.items())))
# [('person2', {'name': 'Anna', 'age': 24}),
#  ('person1', {'name': 'John', 'age': 36})]

print(list(reversed(v['person2'])))
print(list(reversed(v['person2'].keys())))
# ['age', 'name']

print(list(reversed(v['person2'].values())))
# [24, 'Anna']

print(list(reversed(v['person2'].items())))
# [('age', 24), ('name', 'Anna')]