set.union accepts not set iterables for all but the first argument.

[krastanov-stefan]

BPO	15085
Nosy	@bitdancer

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2012-06-16.14:02:45.958>
created_at = <Date 2012-06-16.09:09:08.532>
labels = ['invalid']
title = 'set.union accepts not set iterables for all but the first argument.'
updated_at = <Date 2012-06-16.14:02:45.956>
user = 'https://bugs.python.org/krastanov-stefan'

bugs.python.org fields:

activity = <Date 2012-06-16.14:02:45.956>
actor = 'r.david.murray'
assignee = 'none'
closed = True
closed_date = <Date 2012-06-16.14:02:45.958>
closer = 'r.david.murray'
components = ['None']
creation = <Date 2012-06-16.09:09:08.532>
creator = 'krastanov-stefan'
dependencies = []
files = []
hgrepos = []
issue_num = 15085
keywords = []
message_count = 2.0
messages = ['162962', '162973']
nosy_count = 2.0
nosy_names = ['r.david.murray', 'krastanov-stefan']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue15085'
versions = ['Python 2.7']

[krastanov-stefan]

>>> set.union(set([1,2]), [3])
set([1, 2, 3])

>>> set.union([1,2], [3])
TypeError: descriptor 'union' requires a 'set' object but received a 'list'

It seems a bit inconsistent. Is it justified somehow?

[bitdancer]

By calling 'set.union' you are calling the method on the class. When you call a method directly on a class object, you have to explicitly pass in 'self'. Thus the first argument when you call it like that must be a set object.