python dict.fromkeys() returns empty

python dict.fromkeys() returns empty

By : BudimÄn
Date : November 18 2020, 07:00 PM
This might help you I wrote the following function. It returns an empty dictionary when it should not. The code works on the command line without function. However I cannot see what is wrong with the function, so I have to appeal to your collective intelligence. , fromkeys is a class method, meaning
code :

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Passing in a new value to each key using Python's `dict.fromkeys`

Passing in a new value to each key using Python's `dict.fromkeys`

By : Jason Ko
Date : March 29 2020, 07:55 AM
may help you . How can I get around this limitation: , Then don't give them the same instance of the object.
code :
test_dict = dict((x, dict()) for x in ['k1', 'k2'])
dict.fromkeys method in Python 3.2

dict.fromkeys method in Python 3.2

By : Bidaya APP
Date : March 29 2020, 07:55 AM
wish helps you I want to create the new dictionary that contents a dictionary with lists. My code is: , I'd simply use a dict comprehension instead:
code :
>>> SERVICES = "FTP Download", "FTP Upload", "HTTP"
>>> received = {k: {'MS1': []} for k in SERVICES}
>>> received
{'FTP Download': {'MS1': []}, 'HTTP': {'MS1': []}, 'FTP Upload': {'MS1': []}}
>>> received["HTTP"]["MS1"].append(17)
>>> received
{'FTP Download': {'MS1': []}, 'HTTP': {'MS1': [17]}, 'FTP Upload': {'MS1': []}}
>>> received = dict.fromkeys(SERVICES , {'MS1':[]})
>>> received.values()
dict_values([{'MS1': []}, {'MS1': []}, {'MS1': []}])
>>> [id(v) for v in received.values()]
[141458940, 141458940, 141458940]
Using dict.fromkeys(), assign each value to an empty dictionary

Using dict.fromkeys(), assign each value to an empty dictionary

By : Heka
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further The problem is that {} is a single value to fromkeys, and not a factory. Therefore you get the single mutable dict, not individual copies of it.
defaultdict is one way to create a dict that has a builtin factory.
code :
from collections import defaultdict as dd
from pprint import pprint as pp

a = dd(dict)
for key in range(3):
    a[key][0] = key

a = {key: {} for key in range(3)}
a = {key: {0: key} for key in range(3)}
Python: Why does the dict.fromkeys method not produce a working dicitonary

Python: Why does the dict.fromkeys method not produce a working dicitonary

By : Beatrice
Date : March 29 2020, 07:55 AM
will help you fromkeys(S, v) sets all of the keys in S to the same value v. Meaning that all of the keys in your dictionary new_dict refer to the same dictionary object, not to their own copies of that dictionary.
To set each to a different dict object you cannot use fromkeys. You need to just set each key to a new dict in a loop.
code :
{i: {a: 0 for a in aas} for i in ref_range}
python dict.fromkeys with function as parameter

python dict.fromkeys with function as parameter

By : Masoud.A
Date : March 29 2020, 07:55 AM
may help you . dict.fromkeys() will set all keys to a the same, single value. You can't use it to set to multiple distinct values.
Use zip() to pair up your keys and values, then pass the resulting sequence of (key, value) pairs to the dict() type directly:
code :
classes = ('colore1', 'colore2', 'colore3', 'colore4', 'colore5', 'colore6', 'colore7', 'colore8', 'colore9', 'colore10')
result = dict(zip(set(test_input), classes))
>>> classes = ('colore1', 'colore2', 'colore3', 'colore4', 'colore5', 'colore6', 'colore7', 'colore8', 'colore9', 'colore10')
>>> dict(zip(set(test_input), classes))
{33: 'colore1', 103: 'colore2', 73: 'colore3', 83: 'colore4', 53: 'colore5', 23: 'colore6', 93: 'colore7', 63: 'colore8'}
result = {key: 'colore{}'.format(i) for i, key in enumerate(set(test_input), 1)}
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