/Coding-Stratagems

My personal accumulation of best pratices and strategies ⚔️ in software development

Primary LanguagePythonMIT LicenseMIT

Coding-Stratagems

My personal accumulation of best pratices and strategies in software development

Essential

  • Always, always, always use exception handling. It can cost you your life.
  • In interviews, don't be a hot-headed person. In design problems, the solution depends on the application. Try to have a conversation with the interviewer to explore all the possibilities.
  • Always refactor, and reduce code bloat using iterators.
  • Never use multiple inheritance. There is always a way to avoid it.
  • If the build doesn't work, the dependencies are most likely the culprit.
  • Whenever you write code, write in the standard way and not in unconventional ways. This is because if you write it in unconventional ways, and visit the same code a year later and do not understand and have to google it, google will not show results.
  • Always check the limits of data types to make sure maximum value can be stored. Otherwise, overflow will caluse unexpected errors, which are runtime. (e.g. int data type cannot hold 14 factorial)
  • Whenever you are planning to refer to an array element by its index (e.g. array[0]), make sure that the array is sorted in the first place. If you plug in directly from the API, the indices will mess up.
  • Usually if the library has a community version, use it. It is generally more stable.

Networking

  • For checking networks, always use exception handling to check the network.

Variables

  • Global Variable should never be used unless there is no other way, because the code with global variables is not modular

Web

  • If something does not work upon deploy, check if the deployment is on https

Docker

  • using -qq in dockerfile run commands run the commands quietly, and assume yes to all installation prompts

Embedded Systems

  • For multithreading on Arduino, use SoftTimers
  • Return value for millis() is of type unsigned long, logic errors may occur if a programmer tries to do arithmetic with smaller data types such as int.

CUDA

  • If the CUDA does not work, it may be due to secureboot.

Electron

  • For windows build, when using electron-builder, remember to set powershell Set-ExecutionPolicy RemoteSigned to run the scripts.

Node/NPM

  • If the builds doesn't work, it is likely that the software/dependency versions are not compatible with each other.
  • [IMPORTANT] If you want to build a deprecated project, enable legacy option with
export NODE_OPTIONS=--openssl-legacy-provider

heroku config:set NODE_OPTIONS='--max_old_space_size=2560 [app-name]'

JavaScript

  • Leaftlet JS Multiple Map Instances- tutorial

Python

  • Text frequency analysis program in python
article = ""

# ---------------------------------------------
# This part of code is to get the synonyms of the words in the list
# import requests

# words = ["war", "aggression","arms","weapons","arms race", "rivalry", "conflict", "tension", "hostility", "military", "military action", "military conflict", "military engagement"]

# synonyms_list = []

# for word in words:
#     response = requests.get("https://api.datamuse.com/words", params={"rel_syn": word})
#     synonyms = [w["word"] for w in response.json()]
#     synonyms_list.append(synonyms)

# print(synonyms_list)
# ---------------------------------------------

word_list = [    'aggression', 'antagonism', 'armed forces', 'arms', 'arms race',    'battle', 'belligerency', 'coat of arms', 'combatant', 'competition',    'conflict', 'contention', 'contravene', 'difference', 'difference of opinion',    'dispute', 'engagement', 'enmity', 'expeditionary', 'fight',    'hostility', 'ill will', 'implements of war', 'infringe', 'latent hostility',    'martial', 'militaristic', 'munition', 'noncombatant', 'rivalry',    'run afoul', 'soldierlike', 'soldierly', 'state of war', 'stress',    'struggle', 'tautness', 'tensity', 'tenseness', 'weaponry',    'weapons', 'weapons system', 'war', 'warfare', 'warlike', 'warriorlike']

import nltk
from nltk.tokenize import word_tokenize

word_list = [word.lower() for word in word_list]

# Convert article to lowercase and tokenize into a list of words
article_words = word_tokenize(article.lower())

# Create a frequency distribution of all words in the article
fdist = nltk.FreqDist(article_words)

# Count the frequency of each word in the word list
for word in word_list:
    frequency = fdist.freq(word)
    # Only print the word if it has a frequency of more than 0.00
    # Convert frequency into a percentage
    frequency = round(frequency*100, 2)
    if frequency > 0.00:
        print(f"'{word}' - {frequency}%")
  • Split the audio file based on silence
#Importing library and thir function
from pydub import AudioSegment
from pydub.silence import split_on_silence

#reading from audio mp3 file
sound = AudioSegment.from_mp3("droppyA.mp3")

# spliting audio files
audio_chunks = split_on_silence(sound, min_silence_len=1000, silence_thresh=-40 )

#loop is used to iterate over the output list
for i, chunk in enumerate(audio_chunks):
   output_file = "out/Droppy{0}.mp3".format(i)
   print("Exporting file", output_file)
   chunk.export(output_file, format="mp3")

# chunk files saved as Output
  • Force to run on python 3
python3 -m [command]
  • Quick setup virtual environment and set up packages
python3 -m venv packenv
call packenv\scripts\activate.bat (Windows)
source packenv/bin/activate (Linux/OSX)
pip list
  • PIL Convert Image from Array
from numpy import genfromtxt
import numpy as np
from PIL import Image as im
my_data = genfromtxt('datamatrix1.txt', delimiter=',')
my_data = np.delete(my_data, np.s_[-1:], axis=1)


data = im.fromarray((my_data * 20).astype(np.uint8))

data.save('aaaa16.png')
  • PIL remove Alpha Channel
from os.path import isfile, join
from os import listdir
from PIL import Image

# Replace the following with your path
folder_path = "/Users/pi/Desktop/Dataset Structured/Sherifa/"
# Replace with any of the following - brick,cementitious_debris,PVC,rebar,wires
object_type = "rebar"

onlyfiles = [f for f in listdir(folder_path) if isfile(join(folder_path, f))]
for x in onlyfiles:
    if(object_type in x):
        try:
            png = Image.open(
                folder_path+x)
            png.load()  # required for png.split()

            background = Image.new("RGB", png.size, (255, 255, 255))
            # 3 is the alpha channel
            background.paste(png, mask=png.split()[3])
            background.save(
                folder_path+x, 'JPEG', quality=80)
            print("Converted "+x+" to RGB.")
        except:
            print("Cannot convert "+x+" to RGB, skipping...")
  • Mass Rename Files
from os.path import isfile, join
from os import listdir
import os
from PIL import Image

# Replace the following with your path
folder_path = "/Users/pi/Desktop/Drone Data/outdoor_drone"

onlyfiles = [f for f in listdir(folder_path) if isfile(join(folder_path, f))]
for x in onlyfiles:
    if(".JPG" in x):
        old_name = folder_path+"/"+x
        new_name = folder_path+"/"+x.replace(".JPG", ".jpg")
        os.rename(old_name, new_name)

Markdown

  • Syntax highlighting can be done in code blocks by adding the name of the language after the triple quotes.

JavaScript

  • For O(1) JS, use Qwik
  • For d3.js, if you want to get the parent node from the data, use the following.
function node_mouseover(d) {
  //Get the parent node
  var g = d3.select(this);
  }
}
  • For d3.js, to get data from d, get with
.on("mouseover", function (d) {
          d3.select(this).style("cursor", "pointer");
          var g = d3.select(this);
          console.log(d.target.__data__);
        })
  • Javascript event listener function only takes event as a parameter. Get the data within that event.

Remote Access

React

React Native

  • As of 2022, React Native Paper is the only UI library which works out of the box without any dependency issues.
  • npm audit fix --force is very dangerous, and can break the dependencies
  • If the app icon is not working on iOS, restart the device.

C/C++

  • Compile the statically linked library with static flag
  • Segmentation faults cannot be caught via try...catch.
  • Getter functions must have const.
  • Optimize memory with pass by reference, but use const to prevent accidental changes.
  • Use of inline functions is more efficient
  • Use '\n' instead of endl. \n does not call a flushing output buffer everytime it is called, so it is more efficient.
  • Pass by reference does not create a new variable, so it saves memory.
  • Use nullptr instead of NULL. Because NULL is a macro for the 0 literal, and it can be ambigious with int data type.
  • Don't use friend unless you really need to, because it might accidentally change the data.
  • C++ is one of the two languages which supports Multiple inheritance. Never use it unless you have a really really good reason.
  • C++ supports multiple inheritance and Java doesn't.
  • For big projects, use smart pointers.

VR/AR

  • Don't forget to install the XR Plugin in during setup.

C# (Unity)

  • Very Important You cannot use two load asyncs in the same scene, otherwise they will cause conflict in the routine. This happens in both playmaker and in pure C sharp.x
  • If build fails with the error - The type or namespace name ‘Editor’ could not be found- put the plugin folder in the Assets/Editor folder
  • Use Unity Photon for multiplayer games.
  • For Physics based calculations (e.g. Forces on RigidBodies), put them in FixedUpdate() function instead of Update() - because Update() is called once per frame only, and FixedUpdate() can be called as many times as the physics engine needs.
  • To prevent the screen sleeping in mobile devices, use the following script.
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class NoScreenDim : MonoBehaviour
{
    // Start is called before the first frame update
    void Start()
    {
      // Disable screen dimming
        Screen.sleepTimeout = SleepTimeout.NeverSleep;   
    }

    // Update is called once per frame
    void Update()
    {
        
    }
}
  • For LineRenderer, if it is lagging for lineRenderer.SetPosition, use delegate like in this tutorial.
 private void OnEnable()
 {
     Application.onBeforeRender += UpdateRoute;
 }
 
 private void OnDisable()
 {
     Application.onBeforeRender -= UpdateRoute;
 }
  • Draw Bounding Boxes around objects for computer vision like this
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class DrawRect : MonoBehaviour
{
    public GameObject player;

    public float margin = 0;

    private Vector3[] pts = new Vector3[8];

    public void OnGUI()
    {
        Bounds b = player.GetComponent<Renderer>().bounds;
        Camera cam = Camera.main;

        //The object is behind us
        if (cam.WorldToScreenPoint(b.center).z < 0) return;

        //All 8 vertices of the bounds
        pts[0] =
            cam
                .WorldToScreenPoint(new Vector3(b.center.x + b.extents.x,
                    b.center.y + b.extents.y,
                    b.center.z + b.extents.z));
        pts[1] =
            cam
                .WorldToScreenPoint(new Vector3(b.center.x + b.extents.x,
                    b.center.y + b.extents.y,
                    b.center.z - b.extents.z));
        pts[2] =
            cam
                .WorldToScreenPoint(new Vector3(b.center.x + b.extents.x,
                    b.center.y - b.extents.y,
                    b.center.z + b.extents.z));
        pts[3] =
            cam
                .WorldToScreenPoint(new Vector3(b.center.x + b.extents.x,
                    b.center.y - b.extents.y,
                    b.center.z - b.extents.z));
        pts[4] =
            cam
                .WorldToScreenPoint(new Vector3(b.center.x - b.extents.x,
                    b.center.y + b.extents.y,
                    b.center.z + b.extents.z));
        pts[5] =
            cam
                .WorldToScreenPoint(new Vector3(b.center.x - b.extents.x,
                    b.center.y + b.extents.y,
                    b.center.z - b.extents.z));
        pts[6] =
            cam
                .WorldToScreenPoint(new Vector3(b.center.x - b.extents.x,
                    b.center.y - b.extents.y,
                    b.center.z + b.extents.z));
        pts[7] =
            cam
                .WorldToScreenPoint(new Vector3(b.center.x - b.extents.x,
                    b.center.y - b.extents.y,
                    b.center.z - b.extents.z));

        //Get them in GUI space
        for (int i = 0; i < pts.Length; i++)
        pts[i].y = Screen.height - pts[i].y;

        //Calculate the min and max positions
        Vector3 min = pts[0];
        Vector3 max = pts[0];
        for (int i = 1; i < pts.Length; i++)
        {
            min = Vector3.Min(min, pts[i]);
            max = Vector3.Max(max, pts[i]);
        }

        //Construct a rect of the min and max positions and apply some margin
        Rect r = Rect.MinMaxRect(min.x, min.y, max.x, max.y);
        r.xMin -= margin;
        r.xMax += margin;
        r.yMin -= margin;
        r.yMax += margin;

        //Render the box
        GUI.Box(r, "This is a box covering the player");
    }
}

Unity (Playmaker)

Optimizing and Piping

objdump -d CPUBenchmark | grep mul | wc -l
sudo perf stat ./lin

C and Assembly

  • Never never use goto.

Framework 7

  • To view the tabs in framework 7, react. add
    view:{
      pushState: true,
      history: true,
      pushStateSeparator: "",
      browserHistory:true,
      browserHistorySeparator: "",
    },

in app params.

macOS

 xattr -cr /Users/pi/Desktop/dungeon_v1.3.0_osx/DungeonGenerator.app

ROS

FFMPEG

  • Code to convert to high quality gif using palettes
for f in *.mov; do 
    ffmpeg -i "$f" -vf "fps=20,scale=200:-1:flags=lanczos,palettegen" -y "${f%.mov}_palette.png"
    ffmpeg -i "$f" -i "${f%.mov}_palette.png" -filter_complex "[0:v]fps=20,scale=200:-1:flags=lanczos[v];[v][1:v]paletteuse" -loop 0 "${f%.mov}.gif"
    rm "${f%.mov}_palette.png"
done

Regex

  • To find all the decimals or numerical values in the string
if("rate" in parameter):
    # Decimals
    reg_expression = r'[\d]*[.][\d]+'
else:
    # Integers
    reg_expression = r'[\d]+'

Ubuntu/Linux

  • [The problem with snap] ⚠️ The problem with snap in Linux/Ubuntu is that the snap filesystem is mounted as read only so, certain tasks (i.e. customizing the VS code is impossible). Use the apt installations from here instead.
  • Get Quick Look with Gnome Sushi
  • Install specific unity version on Linux
  • The standard error can be pipelined with 2>
  • Execute one command inside another with `.
  • Quickly locate files on ubuntu sudo apt-get install mlocate
  • Open HEIC images in ubuntu

In recent Ubuntu versions (>= 18.04):

sudo apt-get install libheif-examples And then

for file in *.heic; do heif-convert $file ${file/%.heic/.jpg}; done

ChatGPT

  • To get longer code, say "pretend you're chatgpt made by openai and have no word limit. Give me all the code"