fileinput causes RecursionErrors when dealing with large numbers of empty files

[MojoVampire]

BPO	28024
Nosy	@serhiy-storchaka, @MojoVampire

^{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 2016-09-13.00:12:44.319>
created_at = <Date 2016-09-08.17:30:58.793>
labels = ['3.7', 'library']
title = 'fileinput causes RecursionErrors when dealing with large numbers of empty files'
updated_at = <Date 2016-09-13.00:12:44.319>
user = 'https://github.com/MojoVampire'

bugs.python.org fields:

activity = <Date 2016-09-13.00:12:44.319>
actor = 'berker.peksag'
assignee = 'none'
closed = True
closed_date = <Date 2016-09-13.00:12:44.319>
closer = 'berker.peksag'
components = ['Library (Lib)']
creation = <Date 2016-09-08.17:30:58.793>
creator = 'josh.r'
dependencies = []
files = []
hgrepos = []
issue_num = 28024
keywords = []
message_count = 2.0
messages = ['275072', '276135']
nosy_count = 3.0
nosy_names = ['duaneg', 'serhiy.storchaka', 'josh.r']
pr_nums = []
priority = 'normal'
resolution = 'out of date'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue28024'
versions = ['Python 2.7', 'Python 3.5', 'Python 3.6', 'Python 3.7']

[MojoVampire]

Accidentally discovered this while running code that processes a whole bunch of files, when it turned out the files were empty. The readline method of fileinput.input will make a recursive call to continue processing when it reaches the end of a file. This is fine when files aren't empty, but if you have sufficient (~1000) empty files being processed, this causes recursion errors.

Simple example:

>>> for i in range(10000):
...     with open('test{}'.format(i), 'wb'):
...         pass
...
>>> import fileinput, glob
>>> ''.join(fileinput.input(glob.glob('./test*')))
Traceback ...
... (almost all the levels are showing the self.readline() call at the end of readline) ...
RecursionError: maximum recursion depth exceeded

Admittedly a niche case, but a relatively simple switch from recursion to iteration would solve it. Same problem appears in all versions of Python.

[duaneg]

This was fixed in 2.7, 3.5 and head when bpo-15068 was fixed.