helper_functions

This repository contains some commonly used helper functions. It's mainly for personal use but you are welcome to utilise this repository if you don't want to spend your worthless time on worthwhile things.

Python

Virtualenv linux:

Python2

sudo apt-get install python-virtualenv
virtualenv *env name*
source *env name*/bin/activate

Python3

sudo pip3 install virtualenv 
virtualenv -p python3 myenv
source *env name*/bin/activate

Jupyter

From inside the virtualenv: pip install ipykernel; ipython kernel install --user --name=*env name*;
To remove virtualenv: ipython kernelspec uninstall project_name
List all kernelspec: jupyter kernelspec list

Conda:

Virtualenv

conda create -n test_env python=3.6.3 anaconda
conda activate testenv

Jupyter

 python -m ipykernel install --user --name *env name* --display-name "display name"
 jupyter kernelspec uninstall *env name*

To install package without using cached package: --no-cache-dir

To import module from another directory: os.sys.path.append('../ModelFiles/ResNet'); import resnet

Understanding args & kwargs

Shell

to find a pattern in all files of a directory: grep -rnw /path/to/directory -e "pattern"

Install CUDA and nvidia-drivers: https://linoxide.com/linux-how-to/install-cuda-ubuntu/ (check compatibility of driver with the CUDA version before proceeding) Make sure to download compatible runfile from nvidia website

Check CUDA version: cat /usr/local/cuda/version.txt

check cuDNN version: cat /usr/include/x86_64-linux-gnu/cudnn_v*.h | grep CUDNN_MAJOR -A 2 || cat /usr/local/cuda/include/cudnn.h | grep CUDNN_MAJOR -A 2

Add a new variable to environment variable: export LD_LIBRARY_PATH=/path/to/library:${LD_LIBRARY_PATH}

Linux screen commands links: 1 2

C++

Compiling a C++ file to object file: g++ -c foo.o -std=c++11 foo.cpp

Linking several or one object file: g++ foo.o foo1.o -o foo

Running the executable: ./foo $args$

Directly compiling and linking: g++ -o foo -std=c++11 foo.cpp

For a general explanation of C++ build system, refer Here

Static libraries When you have several .o files, you can put them together as a library, a static library. In Linux/Mac these static libraries are simply archive files, or .a files. To link several object files in a static library ar -cvq foostatic.a foo1.o foo2.o foo3.o

To verify the static libraries: ar -t foostatic.a This will spit out the object files it is composed up of.

To compile using static library so that the compiler knows to link it later, use: g++ -o output main.cpp foodstatic.a. Or if you have several static libraries in a folder, use: g++ -o output main.cpp -L(path of static library) -l(name of static library)

For eg. to connect with OpenCV libraries: g++ foo.cpp -L/path/to/opencv/lib -lopencv_core -lopencv_imgcodecs. If you want to use further functions of OpenCV not found in these libraries, you might have to link against additional OpenCV libraries.

If it is a frequently used library, you can add the path to LD_LIBRARY_PATH and the compiler will automatically load the libraries from there.

Git

Merging & Branching

Overwriting local changes

Django Server

python manage.py migrate python manage.py makemigrations python manage.py createsuperuser python manage.py collectstatic python manage.py runserver 0.0.0.0:8000

For Production Server

Do not commit __pycache__ folder
On the server, run the command DJANGO_SETTINGS=prod SECRET_KEY=****** python manage.py migrate. Do not run the makemigrations command.
Also, DO NOT make any changes to the authentication model. If yes, then try to migrate on the prod server asap and see if it goes through. If it doesn't, then just roll back.

System Process - systemctl

Files are at /etc/systemd/system/

Start Service - sudo systemctl start service

Enable Service (used for the first time - creates symlinks) - sudo systemctl enable service

Check Status - sudo systemctl status service

Restart Service - sudo systemctl restart service

Check logs - sudo journalctl -u service

Stop Service - sudo systemctl stop service

Disable Service (delink symlinks) - sudo systemctl disable service

Gunicorn

All the above systemctl commands work here

Edit file - sudo vi /etc/systemd/system/app.service

Django Application - gunicorn app.wsgi:application --bind 0.0.0.0:8000

Flask Application - gunicorn --bind 0.0.0.0:5000 wsgi:app

After making changes to the gunicorn service file - sudo systemctl daemon-reload

Nginx

Edit file - sudo vi /etc/nginx/sites-available/service

Create symlink - sudo ln -sf /etc/nginx/sites-available/service /etc/nginx/sites-enabled/

Verify file - sudo nginx -t

Restart nginx - sudo systemctl restart nginx

Check status - systemctl status nginx

jainshobhit/helper_functions