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Bug in Python3 ('tempfile', 'subprocess', '_hashlib')


Using freshly-updated Cygwin 64-bit under Windows 7 Enterprise Ver 6.1
and Python 3 version 3.6.4.

The execution of the following script:

    import subprocess
    import _hashlib
    import _sha3'pwd')

always results in 'BlockingIOError: [Errno 11] Resource temporarily

I saw this error first in a script that imported 'tempfile' together
with 'subprocess' (in any order):

    import subprocess
    import tempfile'pwd')

I then managed to narrow down the problem to the '_sha3' module.
Notice that you need to import both '_hashlib' and '_sha3' *in that
order*.  If I swap the order and import '_sha3' before '_hashlib', the
error becomes sporadic, sometimes it happens and sometimes not.

This problem makes it impossible to use 'tempfile' and 'subprocess' in
the same script.  My workaround is currently to disable '_sha3' in
'/lib/python3.6/' by adding at line 62:

    __always_supported = __always_supported[0:8]

This problem only happens in Cygwin 64, 32-bit Cygwin works ok.

Can anyone reproduce this problem?

Best regards,


Giuseppe B. Scelsi  (
Senior Design Engineer, Analog Devices Australia Pty Ltd
Unit 3, 97 Lewis Road, Wantirna, Victoria, 3152, AUSTRALIA
Direct: +61 3 9881 9909   Main: +61 3 9881 9999
Fax: +61 3 9881 9988      Web:

Embedded & Digital Signal Processing Software.

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