python

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Could not load the Qt platform plugin “xcb” in “” even though it was found in Rocky Linux 8

I was installing ANSYS 2023 R2 on Rocky Linux 8 and I encoutnered the error

qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: xcb.

Solution

# dnf install python3-qt5
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Compiling pybind11 with GNU-6.5

The Project Website can be found at https://github.com/pybind/pybind11

pybind11 is a lightweight header-only library that exposes C++ types in Python and vice versa, mainly to create Python bindings of existing C++ code. Its goals and syntax are similar to the excellent Boost.Python library by David Abrahams: to minimize boilerplate code in traditional extension modules by inferring type information using compile-time introspection.

The Compiling Steps can be found at https://pybind11.readthedocs.io/en/stable/basics.html

mkdir build
cd build
cmake .. -DDOWNLOAD_EIGEN=ON -DDOWNLOAD_CATCH=ON
make check -j 4
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Creating Virtual Environment with Python using venv

Virtual Environment and Packages

Sometimes there is a need to create virtual environment, a self-contained directory tree that contains a Python installation for a particular version of Python, plus a number of additional packages as there is sometimes a need for specific version of python library. Here come venv

Creating Virtual Environments 

% module load python/3/intel/2020
% python3 -m venv myenv

This will create a myenv directory if it doesn’t exist, and also create directories inside it containing a copy of the Python interpreter, the standard library, and various supporting files. 

% source myenv/bin/activate

Activating the virtual environment will change your shell’s prompt to show what virtual environment you’re using,

(tutorial-env) [user1@hpc-node1 bin]$ python
Python 3.7.4 (default, Nov 22 2019, 21:31:39)
[GCC 7.3.0] :: Intel(R) Corporation on linux
Type "help", "copyright", "credits" or "license" for more information.
Intel(R) Distribution for Python is brought to you by Intel Corporation.
Please check out: https://software.intel.com/en-us/python-distibution
>>> import sys
>>> sys.path
['', '/usr/local/intelpython3/lib/python37.zip', ....., '.....', '/myhome/melvin/python_project/tutorial-env/lib/python3.7/site-packages']
>>>

Managing Packages with pip

You can install, upgrade and remove using a program called pip. By default, pip will install packages from the Python Package Index (http://pypi.org).

You can install the latest version of a package by specifying a package’s name:

(tutorial-env) [user1@hpc-node1 bin]$ python -m pip install novas
Collecting novas
  Downloading https://files.pythonhosted.org/packages/42/95/a05bc35cb119925e10f9faa8a2bd17020b0a585744a38921a709acdd9a14/novas-3.1.1.5.tar.gz (135kB)
    100% |████████████████████████████████| 143kB 4.6MB/s
Installing collected packages: novas
  Running setup.py install for novas ... done
Successfully installed novas-3.1.1.5

You can also install specific version by using the command 

(tutorial-env) [user1@hpc-node1 bin]$ python -m pip install requests==2.6.0
Collecting requests==2.6.0
  Downloading https://files.pythonhosted.org/packages/73/63/b0729be549494a3e31316437053bc4e0a8bb71a07a6ee6059434b8f1cd5f/requests-2.6.0-py2.py3-none-any.whl (469kB)
    100% |████████████████████████████████| 471kB 4.3MB/s
Installing collected packages: requests
Successfully installed requests-2.6.0

You can also upgrade the package by using the command

(tutorial-env) [user1@hpc-node1 bin]$ python -m pip install --upgrade request    s
Collecting requests
  Downloading https://files.pythonhosted.org/packages/29/c1/24814557f1d22c56d50    280771a17307e6bf87b70727d975fd6b2ce6b014a/requests-2.25.1-py2.py3-none-any.whl     (61kB)
    100% |████████████████████████████████| 61kB 3.4MB/s
Collecting chardet<5,>=3.0.2 (from requests)
  Downloading https://files.pythonhosted.org/packages/19/c7/fa589626997dd07bd87    d9269342ccb74b1720384a4d739a1872bd84fbe68/chardet-4.0.0-py2.py3-none-any.whl (1    78kB)
    100% |████████████████████████████████| 184kB 5.3MB/s
Collecting urllib3<1.27,>=1.21.1 (from requests)
  Downloading https://files.pythonhosted.org/packages/0c/cd/1e2ec680ec7b09846dc    6e605f5a7709dfb9d7128e51a026e7154e18a234e/urllib3-1.26.5-py2.py3-none-any.whl (    138kB)
    100% |████████████████████████████████| 143kB 5.9MB/s
Collecting idna<3,>=2.5 (from requests)
  Downloading https://files.pythonhosted.org/packages/a2/38/928ddce2273eaa564f6    f50de919327bf3a00f091b5baba8dfa9460f3a8a8/idna-2.10-py2.py3-none-any.whl (58kB)
    100% |████████████████████████████████| 61kB 4.3MB/s
Collecting certifi>=2017.4.17 (from requests)
  Downloading https://files.pythonhosted.org/packages/05/1b/0a0dece0e8aa492a6ec    9e4ad2fe366b511558cdc73fd3abc82ba7348e875/certifi-2021.5.30-py2.py3-none-any.wh    l (145kB)
    100% |████████████████████████████████| 153kB 5.1MB/s
Installing collected packages: chardet, urllib3, idna, certifi, requests
  Found existing installation: requests 2.6.0
    Uninstalling requests-2.6.0:
      Successfully uninstalled requests-2.6.0
Successfully installed certifi-2021.5.30 chardet-4.0.0 idna-2.10 requests-2.25.    1 urllib3-1.26.5

You can display all the packages in the environment in virtual environment

(tutorial-env) [user1@hpc-node1 bin]$ pip list
Package    Version
---------- ---------
certifi    2021.5.30
chardet    4.0.0
idna       2.10
novas      3.1.1.5
pip        19.0.3
requests   2.25.1
setuptools 40.8.0
urllib3    1.26.5

pip freeze can be used to produce a similar list of installed packages and formatted in a output file that pip install can read from

(tutorial-env) [user1@hpc-node1 bin]$ pip freeze > requirements.txt
(tutorial-env) [user1@hpc-node1 bin]$ cat requirements.txt
certifi==2021.5.30
chardet==4.0.0
idna==2.10
novas==3.1.1.5
requests==2.25.1
urllib3==1.26.5

Install all the necessary packages with install -r from requirements.txt

(tutorial-env) [user1@hpc-node1 bin]$ python -m pip install -r requirements.txt
Requirement already satisfied: certifi==2021.5.30 in /myhome/melvin/python_project/tutorial-env/lib/python3.7/site-packages (from -r requirements.txt (line 1)) (2021.5.30)
Requirement already satisfied: chardet==4.0.0 in /myhome/melvin/python_project/tutorial-env/lib/python3.7/site-packages (from -r requirements.txt (line 2)) (4.0.0)
Requirement already satisfied: idna==2.10 in /myhome/melvin/python_project/tutorial-env/lib/python3.7/site-packages (from -r requirements.txt (line 3)) (2.10)
Requirement already satisfied: novas==3.1.1.5 in /myhome/melvin/python_project/tutorial-env/lib/python3.7/site-packages (from -r requirements.txt (line 4)) (3.1.1.5)
Requirement already satisfied: requests==2.25.1 in /myhome/melvin/python_project/tutorial-env/lib/python3.7/site-packages (from -r requirements.txt (line 5)) (2.25.1)
Requirement already satisfied: urllib3==1.26.5 in /myhome/melvin/python_project/tutorial-env/lib/python3.7/site-packages (from -r requirements.txt (line 6)) (1.26.5)

References:

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Python [Errno 13] Permission denied

Issues

If you are facing issues like this when using python libraries like “queue = multiproccesing.Queue()”, you may face this issue

Error:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/local/intel/2020/intelpython3/lib/python3.7/multiprocessing/context.py", line 102, in Queue
return Queue(maxsize, ctx=self.get_context())
File "/usr/local/intel/2020/intelpython3/lib/python3.7/multiprocessing/queues.py", line 42, in __init__
self._rlock = ctx.Lock()
File "/usr/local/intel/2020/intelpython3/lib/python3.7/multiprocessing/context.py", line 67, in Lock
return Lock(ctx=self.get_context())
File "/usr/local/intel/2020/intelpython3/lib/python3.7/multiprocessing/synchronize.py", line 162, in __init__
SemLock.__init__(self, SEMAPHORE, 1, 1, ctx=ctx)
File "/usr/local/intel/2020/intelpython3/lib/python3.7/multiprocessing/synchronize.py", line 59, in __init__
unlink_now)
PermissionError: [Errno 13] Permission denied

When executing the code with root privilege, it was working fine, but a normal user doesn’t have permission to access shared memory.

Resolution:

You can counter-check the issue by checking /dev/shm

% ls -ld /dev/shm

Change Permission to 777

% chmod 777 /dev/shm

Turn on the sticky bit

% chmod +t /dev/shm
% ls -ld /dev/shm
drwxrwxrwt 4 root root 520 Mar 5 13:32 /dev/shm
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Encountering Error when pip install TensorToolbox

I’m using Python-3.8.7  When I do a pip install for TensorFlowbox with Intel Optimized Toolbox, I received errors.

% pip install TensorFlowbox

But it failed with its SpectralToolbox Dependencies.

.....
.....

Building wheels for collected packages: SpectralToolbox, orthpol-light
Building wheel for SpectralToolbox (setup.py) ... error
ERROR: Command errored out with exit status 1:
command: /usr/local/python/intel/2017u3/intelpython3/bin/python -u -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-p5qjlor0/spectraltoolbox/setup.py'"'"'; __file__='"'"'/tmp/pip-install-p5qjlor0/spectraltoolbox/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' bdist_wheel -d /tmp/pip-wheel-4k6ars4d
cwd: /tmp/pip-install-p5qjlor0/spectraltoolbox/
Complete output (56 lines):

Somehow the later version of Python3 has issues with SpectralToolbox and TensorToolbox. To compile TensorToolbox, you have to go back to earlier version of Python 3. I chose Python-3.6.9 (https://www.python.org/downloads/release/python-369/).

And it works.

Perquisites:

openmpi-3.1.4
gnu-6.5
m4-1.4.18
gmp-6.1.0
mpfr-3.1.4
mpc-1.0.3
isl-0.18
gsl-2.1

 

Compile

% tar -zxvf Python-3.6.9
% cd Python-3.6.9
% ./configure --prefix=/usr/local/python-3.6.9 --enable-optimizations
% make -j 16
% make install

Installing TensorToolbox

% pip install numpy scipy matplotlib
% pip install mpi4py
% pip install TensorToolbox

For more information, see TensorToolbox-1.0.22 (https://pypi.org/project/TensorToolbox/#description)

 

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Test Failed… does not support .pth files

If you are doing a setup.py with specific directories

python setup.py install --prefix=/home/user1

If you are getting a PythonPath Error something like this.

TEST FAILED: /home/user1/lib/python3.7/site-packages/ does NOT support .pth files error: bad install directory or PYTHONPATH

You are attempting to install a package to a directory that is not on PYTHONPATH and which Python does not read ".pth" files from. 
The installation directory you specified (via --install-dir, --prefix, or the distutils default setting) was: /home/user1/lib/python3.7/site-packages/

and your PYTHONPATH environment variable currently contains:

You can solve like by putting in your .bashrc.

export PYTHONPATH="${PYTHONPATH}:/home/user1/lib/python3.7/site-packages/"
source ~/.bashrc