Lambda, Enumerate and List comprehensions crash

[wilsoncampusano]

BPO	22075
Nosy	@ned-deily
Files	test_c.py: code that crash test_c.py: Code that crash

^{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 2014-07-26.02:46:41.468>
created_at = <Date 2014-07-26.02:00:10.970>
labels = ['interpreter-core', 'invalid', 'type-crash']
title = 'Lambda, Enumerate and List comprehensions crash'
updated_at = <Date 2014-07-26.02:46:41.467>
user = 'https://bugs.python.org/wilsoncampusano'

bugs.python.org fields:

activity = <Date 2014-07-26.02:46:41.467>
actor = 'ned.deily'
assignee = 'none'
closed = True
closed_date = <Date 2014-07-26.02:46:41.468>
closer = 'ned.deily'
components = ['Interpreter Core']
creation = <Date 2014-07-26.02:00:10.970>
creator = 'wilsoncampusano'
dependencies = []
files = ['36097', '36099']
hgrepos = []
issue_num = 22075
keywords = []
message_count = 3.0
messages = ['224015', '224017', '224018']
nosy_count = 2.0
nosy_names = ['ned.deily', 'wilsoncampusano']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue22075'
versions = ['Python 2.7']

[wilsoncampusano]

SO: Ubuntu 14.04

When i run this code my pc crash

[wilsoncampusano]

SO: Ubuntu 14.04

When i run this code my pc crash

[ned-deily]

It may be hard to see what's going on with the code written as a list comprehension. We could expand it out to something roughly equivalent and print the first n iterations:

def main():
    lista =[1, 4, 5 , 5, 6 , 3 ,1]
    def ins(x):
        return lista.insert(x,0)

    for idx, v in enumerate(lista):
        if v == 5:
            ins(idx)
            print(idx, lista)
        if idx > 10:
            break

if __name__ == '__main__':
	main()

(2, [1, 4, 0, 5, 5, 6, 3, 1])
(3, [1, 4, 0, 0, 5, 5, 6, 3, 1])
(4, [1, 4, 0, 0, 0, 5, 5, 6, 3, 1])
(5, [1, 4, 0, 0, 0, 0, 5, 5, 6, 3, 1])
(6, [1, 4, 0, 0, 0, 0, 0, 5, 5, 6, 3, 1])
(7, [1, 4, 0, 0, 0, 0, 0, 0, 5, 5, 6, 3, 1])
(8, [1, 4, 0, 0, 0, 0, 0, 0, 0, 5, 5, 6, 3, 1])
(9, [1, 4, 0, 0, 0, 0, 0, 0, 0, 0, 5, 5, 6, 3, 1])
(10, [1, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5, 5, 6, 3, 1])
(11, [1, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5, 5, 6, 3, 1])

Because the list is mutating by inserting the 0 before the 5, once the 5 entry is found, it keeps "moving" to the right so the loop never terminates and lista keeps expanding until Python runs out of memory. Don't do that!