*Memo:
- My post explains dictionary functions (1).
- My post explains dictionary functions (2).
- My post explains a dictionary (1).
fromkeys() can create a dictionary with pairs of a key and default value as shown below:
*Memo:
- The 1st argument is
iterable
(Required-Type:Iterable):- Don't use
iterable=
.
- Don't use
- The 2nd argument is
value
(Optional-Default:None
-Type:Any or NoneType) to set its default value with the keys ofiterable
:- Don't use
value=
.
- Don't use
# 1D dictionary
print(dict.fromkeys(['A', 'B', 'C']))
print(dict.fromkeys(['A', 'B', 'C'], None))
# {'A': None, 'B': None, 'C': None}
# 1D dictionary
print(dict.fromkeys(['A', 'B', 'C'], 'X'))
# {'A': 'X', 'B': 'X', 'C': 'X'}
# 2D dictionary
print(dict.fromkeys(['A', 'B', 'C'], {'X':'Y'}))
# {'A': {'X': 'Y'}, 'B': {'X': 'Y'}, 'C': {'X': 'Y'}}
# 3D dictionary
print(dict.fromkeys(['A', 'B', 'C'], {'X':{'Y':'Z'}}))
# {'A': {'X': {'Y': 'Z'}}, 'B': {'X': {'Y': 'Z'}}, 'C': {'X': {'Y': 'Z'}}}
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=
.
- Don't use
- 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.
- Be careful,
<1D dictionary>:
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)]
<2D dictionary>:
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=
.
- Don't use
- By default, the list which has the zero or more keys of a dictionary is used.
<1D dictionary>:
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')]
<2D dictionary>:
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')]
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