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Generator as *args: TypeError replaced #58112

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tifv mannequin opened this issue Jan 29, 2012 · 2 comments
Closed

Generator as *args: TypeError replaced #58112

tifv mannequin opened this issue Jan 29, 2012 · 2 comments
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interpreter-core (Objects, Python, Grammar, and Parser dirs) type-bug An unexpected behavior, bug, or error

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@tifv
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Mannequin

tifv mannequin commented Jan 29, 2012

BPO 13904
Nosy @terryjreedy, @tifv
Superseder
  • bpo-4806: Function calls taking a generator as star argument can mask TypeErrors in the generator
    		•
    Files
  • typeerror-replaced-in-stararg.diff: patch
  • typeerror-replaced-in-stararg-test.diff: test
    		•

    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 2012-02-04.02:12:56.120>
created_at = <Date 2012-01-29.16:38:40.303>
labels = ['interpreter-core', 'type-bug']
title = 'Generator as *args: TypeError replaced'
updated_at = <Date 2012-02-04.02:12:56.020>
user = 'https://github.com/tifv'

    bugs.python.org fields:

    activity = <Date 2012-02-04.02:12:56.020>
actor = 'terry.reedy'
assignee = 'none'
closed = True
closed_date = <Date 2012-02-04.02:12:56.120>
closer = 'terry.reedy'
components = ['Interpreter Core']
creation = <Date 2012-01-29.16:38:40.303>
creator = 'july'
dependencies = []
files = ['24358', '24359']
hgrepos = []
issue_num = 13904
keywords = ['patch']
message_count = 2.0
messages = ['152243', '152579']
nosy_count = 2.0
nosy_names = ['terry.reedy', 'july']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = None
status = 'closed'
superseder = '4806'
type = 'behavior'
url = 'https://bugs.python.org/issue13904'
versions = ['Python 2.7', 'Python 3.2', 'Python 3.3']
    @tifv
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    Mannequin Author

    tifv mannequin commented Jan 29, 2012 

    >>> set().union(*(None[k] for k in range(5)))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: union() argument after * must be a sequence, not generator

    Clearly, exception in not relevant, since next line works:

    >>> set().union(*([k] for k in range(5)))
{0, 1, 2, 3, 4}

    Correct exception would be

    >>> None[1]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'NoneType' object is not subscriptable

    Problem is in python function call mechanics.
    set().union can be replaced by any callable;
    Generator can be replaced by any TypeError-raising iterable. Exceptions other then TypeError are handled correctly.

    Python/ceval.c:4322
    ext_do_call() converts stararg to tuple.
    If any TypeError is raised, it is replaced with
    TypeError("%s argument after * must be a sequence, not %s")

    Proposed solution:

    Probably, we can avoid replacing TypeError. Exceptions in the above cases would become relevant, and

    >>> int(*None)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: type object argument after * must be a sequence, not NoneType

    would become

    >>> int(*None)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'NoneType' object is not iterable

    so exception is still recognizable (and, may be, even more relevant, since we don't actually need _sequence_ as stararg, _iterable_ would be enough).

    @tifv tifv mannequin added interpreter-core (Objects, Python, Grammar, and Parser dirs) type-bug An unexpected behavior, bug, or error labels Jan 29, 2012
    @terryjreedy
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    I unlinked to see if I could link it to 4806 instead. Did not work. Please nosy yourself there and upload your files to *that* issue.

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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