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bpo-30030: Reimplement tempfile._RandomNameSequence using a generator function. #1075

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Merged
serhiy-storchaka merged 1 commit into from
Apr 11, 2017
Merged

bpo-30030: Reimplement tempfile._RandomNameSequence using a generator function. #1075

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35 changes: 12 additions & 23 deletions Lib/tempfile.py
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Original file line number Diff line number Diff line change
Expand Up @@ -133,32 +133,21 @@ def _sanitize_params(prefix, suffix, dir):
return prefix, suffix, dir, output_type


class _RandomNameSequence:
"""An instance of _RandomNameSequence generates an endless
sequence of unpredictable strings which can safely be incorporated
into file names. Each string is six characters long. Multiple
threads can safely use the same instance at the same time.

_RandomNameSequence is an iterator."""
def _RandomNameSequence():
"""Generate an endless sequence of unpredictable strings which
can safely be incorporated into file names. Each string is 8
characters long. Multiple threads and forked processes can
safely use the same instance at the same time."""

characters = "abcdefghijklmnopqrstuvwxyz0123456789_"

@property
def rng(self):
rng_pid = None
while True:
cur_pid = _os.getpid()
if cur_pid != getattr(self, '_rng_pid', None):
self._rng = _Random()
self._rng_pid = cur_pid
return self._rng

def __iter__(self):
return self

def __next__(self):
c = self.characters
choose = self.rng.choice
letters = [choose(c) for dummy in range(8)]
return ''.join(letters)
if cur_pid != rng_pid:
choose = _Random().choice
rng_pid = cur_pid
letters = [choose(characters) for dummy in range(8)]
yield ''.join(letters)

def _candidate_tempdir_list():
"""Generate a list of candidate temporary directories which
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5 changes: 3 additions & 2 deletions Lib/test/test_tempfile.py
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
# tempfile.py unit tests.
import collections.abc
import tempfile
import errno
import io
Expand Down Expand Up @@ -290,9 +291,9 @@ class TestGetCandidateNames(BaseTestCase):
"""Test the internal function _get_candidate_names."""

def test_retval(self):
# _get_candidate_names returns a _RandomNameSequence object
# _get_candidate_names returns an iterator
obj = tempfile._get_candidate_names()
self.assertIsInstance(obj, tempfile._RandomNameSequence)
self.assertIsInstance(obj, collections.abc.Iterator)

def test_same_thing(self):
# _get_candidate_names always returns the same object
Expand Down