Questions tagged [frozenset]
66 questions
43
votes
2 answers
Set vs. frozenset performance
I was tinkering around with Python's set and frozenset collection types.
Initially, I assumed that frozenset would provide a better lookup performance than set, as its immutable and thus could exploit the structure of the stored items.
However, this…
Sven Hager
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19
votes
5 answers
'frozenset' object is not callable
When I attempt to import hashlib in any context, it throws this error:
File "", line 1, in
File "build/bdist.macosx-10.11-intel/egg/hashlib.py", line 115, in
"""
TypeError: 'frozenset' object is not callable
Any idea…
Alex Beals
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15
votes
5 answers
What are the differences between Set, FrozenSet, MutableSet and AbstractSet in python typing module?
I am trying to annotate my code with types but I am a little confused when it comes to sets. I read some points in PEP 484:
Note: Dict , List , Set and FrozenSet are mainly useful for annotating return values. For arguments, prefer the abstract…
marcotama
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14
votes
3 answers
Is it safe to use frozen set as Dict key?
It obviously works but are there cases where two sets of same elements happen to add two entries in Dict? I guess I got this condition earlier and changed my code from frozenset(...) to tuple(sorted(frozenset(...))). Can someone who knows how Dict…
balki
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5
votes
4 answers
Which takes less memory, a frozenset or a tuple?
I have an object which needs to be "tagged" with 0-3 strings (out of a set of 20-some possibilities); these values are all unique and order doesn't matter. The only operation that needs to be done on the tags is checking if a particular one is…
Draconis
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5
votes
3 answers
Maintaining the order of the elements in a frozen set
I have a list of tuples, each tuple of which contains one string and two integers. The list looks like this:
x = [('a',1,2), ('b',3,4), ('x',5,6), ('a',2,1)]
The list contains thousands of such tuples. Now if I want to get unique combinations, I…
mlRocks
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5
votes
2 answers
Python - issue with using a list of frozenset entries in a for loop
I am trying to learn the apriori machine learning algorithm from a book that uses Python, and as part of that learning, I am currently stuck with this following problem:
The following code construct seems to work fine:
Ck = [[1], [2], [3], [4],…
user3755648
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5
votes
1 answer
Different python frozensets with same hash value
My understanding is that hashing two different frozensets (immutable Python sets), which need to contain hashable objects, should lead to two different hashes. Why do I get the output below for two different frozensets?
In [11]: a
Out[11]:…
Roy
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4
votes
2 answers
How is frozenset equality implemented in Python?
How is frozenset equality implemented in CPython? In particular, I want to know how individual elements in the fronzenset are compared with each other and their total time complexity.
I took a look at set and frozenset difference in implementation…
James Parker
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4
votes
1 answer
Complexity of converting a set to a frozenset in Python
What is the computational complexity of "freezing" a set in Python?
For example, does the second line in
a = {1,2,3}
b = frozenset(a)
require O(n) time? Or is it simply a "view" created in constant time?
erensezener
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3
votes
1 answer
numpy.unique has the problem with frozensets
Just run the code:
a = [frozenset({1,2}),frozenset({3,4}),frozenset({1,2})]
print(set(a)) # out: {frozenset({3, 4}), frozenset({1, 2})}
print(np.unique(a)) # out: [frozenset({1, 2}), frozenset({3, 4}), frozenset({1, 2})]
The first out is correct,…
klapeyron
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3
votes
2 answers
Extract string from rules frozensets
With the following statement:
rules = association_rules(frequent_itemsets, metric="lift", min_threshold=1.2)
I get a data frame of rules in the format:
frozenset({'Co_Apples'})
But I need to extract a Co_Apples as a string.
How can I do that?
Erez Ben-Moshe
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3
votes
2 answers
Time-complexity of checking if two frozensets are equal in Python
Couldn't find the details of this anywhere online, when comparing two frozensets does Python iterate through the elements in one of the sets or does it check the hash values of the frozensets since frozensets are hashable?
SW Williams
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3
votes
1 answer
Add the empty set to a family of sets in a frozenset in python
Suppose I generate a frozenset with
A = frozenset(frozenset([element]) for element in [1,2,3])
And I have the empty set
E = frozenset(frozenset())
Now I want to have the union of both sets:
U = A | E
This gives me
frozenset({frozenset({2}),…
Johannes Bleher
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3
votes
5 answers
Immutable Dictionary with key-object pairs Python
I have a dictionary filled with key-object pairs. I want to make the dictionary immutable and I thought the best/easiest way is to cast it to a frozenset but frozenset(dict) and also tuple(dict) only stores the keys.
Using frozenset(dict.items()) I…
ThunderM
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