DEV Community: kk1123

Python Basic

kk1123 — Mon, 03 Nov 2025 07:30:05 +0000

Set

# set
set1  = set([1,2,2,1])
set2  = set([3,2,1,1])
set1, set2
set1.add(3)
set2.add(6)
set1, set2
set1.remove(1)
set1 & set2
set3 = set1.union(set2)
set3.issuperset(set1)
set1.issubset(set3)
set1.difference([1])
.clear()
update()
pop()

Tuples

Difference types of data collect in a tuple.
Ordered.

me = ("keke",26,"beauty",(170,52),("cs","ai"))
me
meme = me + ("kek",1)
meme
meme[1]
meme[-1]
meme[3][0]
meme[1:3]

List

dataList = [1,'1',"true"]
dataList.extend([2,4])
dataList.append([3,3])
dataList
del(dataList[0])
dataList
dataList[0:3]

Dictionary

me = {"name":"keke","age":18,1:3,(1,2):[3]}
me["name"]
me.keys()
me.values()
me["name"]+"o"
items()
copy()
clear()

Loop

range(3)
range(0,3)# genarate number from 0 to 2

Function

def name (para):
help(add)

Predefined funciton

sum((1,1))
len((1,1))

prepare python environment

kk1123 — Sun, 26 Oct 2025 15:20:29 +0000

Create virtual environment

Create a project folder
Cd to the project folder
Create virtual environment: conda create -n ai_painting python=3.10
Activate virtual environment: conda activate ai_painting

Install librarys

Install CPU torch pip install torch trochvision trochaudio
Install AI painting libraries pip install diffusers["torch"] transformers accelerate
Install web framework:pip install "fastapi[standard]"

Test Installing

Create a python file:

import torch
from diffusers import StableDiffusionPipeline
import gc  # Garbage collector

print("🔧 Setting up optimized AI system...")

# Force CPU and clear memory
device = "cpu"
torch.cuda.empty_cache() if torch.cuda.is_available() else None
gc.collect()

print("🚀 Loading model with memory optimization...")

try:
    # Load with memory optimizations
    model_id = "runwayml/stable-diffusion-v1-5"

    # Load to CPU with specific settings for stability
    pipe = StableDiffusionPipeline.from_pretrained(
        model_id,
        torch_dtype=torch.float32,  # Use float32 for CPU stability
        use_safetensors=True
    )
    pipe = pipe.to(device)

    # Disable the safety checker to save memory
    pipe.safety_checker = None
    pipe.requires_safety_checker = False

    print("✅ Model loaded! Generating smaller test image...")

    # Generate a smaller image to save memory
    prompt = "a simple red apple on a table"

    with torch.no_grad():
        image = pipe(
            prompt,
            num_inference_steps=20,  # Fewer steps = less memory
            guidance_scale=7.5,
            width=256,  # Smaller image
            height=256   # Smaller image
        ).images[0]

    image.save("test_small.jpg")
    print("📁 Success! Image saved as 'test_small.jpg'")

except Exception as e:
    print(f"❌ Error: {e}")

how to push a local code repository to a remote repository

kk1123 — Mon, 26 May 2025 16:04:13 +0000

1. init your local local repository

cd /path/to/your/project      # Go to your project directory
git init                      # Initialize a Git repository
git add .                     # Add all files
git commit -m "Initial commit"  # Commit the changes

2. Push the local repository to the remote

git remote add origin https://github.com/kkju1123/courseSummary.git
git branch -M main            # Rename to 'main' (optional but standard)
git push -u origin main       # Push to GitHub

3. what does -u mean

-u is short for --set-upstream
From now on, link the local main branch to the origin/main branch on GitHub, so you don’t need to specify them every time.

Binary Search

kk1123 — Wed, 14 May 2025 13:33:15 +0000

class Solution {
    public int searchInsert(int[] nums, int target) {
        int low = 0, high = nums.length-1;
        while(low <= high){
            int mid = (high-low)/2+low;
            if(nums[mid] == target){
                return mid;
            }
            else if(nums[mid]>target){
                high = mid-1;
            }
            else{
                low = mid+1;
            }
        }
        return low;
    }
}

Java Tutorial-What is Java

kk1123 — Sat, 03 May 2025 18:04:36 +0000

Java is a high-level, object-oriented programming language used to build applications across platforms—from web and mobile apps to enterprise software. It is known for its Write Once, Run Anywhere capability, meaning code written in Java can run on any device that supports the Java Virtual Machine (JVM).

Keywords: high-level,object-oriented,across platforms,write once run everywhere, JVM.

1. What is Java Used For?

Develop mobile apps, desktop apps, web apps, web servers, games, and enterprise-level systems.
Java's syntax is similar to C/C++.

1.1 Java File Naming Conventions

The file name must match with the public class name.
Java is case sensitive, so Geeks.java is not equal to geeks.java.
If a file has no "public" class, the file name can be anything but it should be matched with the primary class name.

2. Java Basic

Java basics form the foundation of your programming journey, covering essential concepts like syntax, data types, variables, loops, and conditionals.

3. Java Methods

Java methods are reusable blocks of code that perform specific tasks and help organize your program.

4. Java Arrays

Java arrays are containers that store multiple values of the same data type in a single variable. They provide an efficient way to** manage and access collections of data** using index-based positions:

5. Java Strings

represent sequences of characters and are widely used in text processing. They are immutable, meaning once created, their values cannot be changed:

6. Java OOPs Concepts

Java follows the Object-Oriented Programming (OOP) paradigm, which organizes code into classes and objects. Core OOP principles like inheritance, encapsulation, polymorphism, and abstraction make Java modular and scalable:

7. Java Interfaces

Java interfaces define a contract that classes must follow, specifying method signatures without implementations. They enable abstraction and support multiple inheritance in Java through a clean, structured approach:

8. Java Collections

Java Collections provide a framework for storing and manipulating groups of objects efficiently. It includes interfaces like List, Set, and Map, along with classes like ArrayList, HashSet, and HashMap:

9. Java Exception Handling

Java Exception Handling is a mechanism to handle runtime errors, ensuring the program runs smoothly without crashing. It uses keywords like try, catch, throw, throws, and finally to manage exceptions:

10. Java Multithreading

Java Multithreading allows concurrent execution of two or more threads, enabling efficient CPU utilization and faster program performance. It is commonly used for tasks like parallel processing and responsive applications:

11. Java File Handling

Java File Handling enables programs to create, read, write, and manipulate files stored on the system. It uses classes from the java.io and java.nio packages for efficient file operations:

12. Java Streams and Lambda Expressions

Java Streams and Lambda Expressions simplify data processing by enabling functional-style operations on collections. Lambdas provide concise syntax for anonymous functions, while Streams allow efficient filtering, mapping, and reduction of data:

13. Java IO

Java IO (Input/Output) provides a set of classes and streams to read and write data from various sources like files, consoles, and network connections. It is part of the java.io package and supports both byte and character streams:

14. Java Synchronization

Java Synchronization is used to control access to shared resources in multithreaded environments. It ensures that only one thread can access a critical section at a time, preventing data inconsistency:

15. Java Regex

Java Regex (Regular Expressions) allows **pattern matching **and text manipulation using the java.util.regex package. It is powerful for validating, searching, and replacing strings based on specific patterns:

16. Java Networking

Java Networking enables communication between devices over a network using classes from the java.net package. It supports protocols like TCP and UDP for building client-server applications and data exchange:

17. Java Memory Allocation

Java Memory Allocation refers to how memory is assigned to variables, objects, and classes during program execution. It involves stack and heap memory, with the JVM managing allocation and garbage collection automatically:

zsh: command not found: gradlew

kk1123 — Thu, 13 Feb 2025 11:09:42 +0000

Use ./gradlew instead of gradlew to tell IDEA that gradle is in the current path

useEffect must not return anything besides a function, which is used for clean-up.

kk1123 — Wed, 25 Dec 2024 08:29:25 +0000

This mistake is caused by returning something in the useEffect function.
Can only return nothing or a clean-up function in useEffect function:

Wrong usage:

 useEffect(()=>getData(),[])

  async function getData() {
    const url = "http://localhost:8080/hello";
    try {
      const response = await fetch(url);
      setData(response)
    } catch (error) {}
  }

getData returns a promise because it is declared to be async. This promise will eventually be resolved when asynchronous operations (like fetch) complete.
Cannot return a promise in useEffect function. Only return nothing or the clean-up function.

Correct usage: write asynchronous functions in useEffect and call them so that the useEffect function returns nothing.

useEffect(() => {
    async function getData() {
      const url = "http://localhost:8080/hello";
      try {
        const response = await fetch(url);
        setData(response);
      } catch (error) {}
    }
    getData();
  }, []);

The source code of useMemo:

kk1123 — Fri, 04 Oct 2024 09:43:31 +0000

There are two kinds of circumstances: mount and update, so useMemo has two implementations: mountMemo and updateMemo.

The source code of mountMemo:

function mountMemo<T>(
  nextCreate: () => T,
  deps: Array<mixed> | void | null,
): T {
  const hook = mountWorkInProgressHook();
  const nextDeps = deps === undefined ? null : deps;
  const nextValue = nextCreate();
  if (shouldDoubleInvokeUserFnsInHooksDEV) {
    setIsStrictModeForDevtools(true);
    nextCreate();
    setIsStrictModeForDevtools(false);
  }
  hook.memoizedState = [nextValue, nextDeps];
  return nextValue;
}

Explanation:
In the mount phase, the useMemo function calls the callback function to calculate and return the value. Save the value and deps into hook.memoizedState.

Use mountWorkInProgressHook to create a hook object.
Save deps in nextDeps.
Call the nextCreate() to get nextValue. If in a dev environment, call twice.
Save the nextValue and nextDeps in the hook.memoizedStateand return nextValue.

The source code of updateMemo:

function updateMemo<T>(
  nextCreate: () => T,
  deps: Array<mixed> | void | null,
): T {
  const hook = updateWorkInProgressHook();
  const nextDeps = deps === undefined ? null : deps;
  const prevState = hook.memoizedState;
  // Assume these are defined. If they're not, areHookInputsEqual will warn.
  if (nextDeps !== null) {
    const prevDeps: Array<mixed> | null = prevState[1];
    if (areHookInputsEqual(nextDeps, prevDeps)) {
      return prevState[0];
    }
  }
  const nextValue = nextCreate();
  if (shouldDoubleInvokeUserFnsInHooksDEV) {
    setIsStrictModeForDevtools(true);
    nextCreate();
    setIsStrictModeForDevtools(false);
  }
  hook.memoizedState = [nextValue, nextDeps];
  return nextValue;
}

Explanation:
In the update phase, React will judge whether the deps have changed or not, if changed, React will run the callback to get the new value and return. If not changed, React will return the old value.

Get a new hook object: hook = updateWorkInProgressHook();
if deps array is empty if (nextDeps !== null), call the callback function every render and return new value.
If the deps array is not empty, judge whether the deps have changed or not if (areHookInputsEqual(nextDeps, prevDeps)). If not changed, return the old value return prevState[0];.

Computer Control in Software

kk1123 — Fri, 09 Aug 2024 03:09:32 +0000

In the context of software, "computer control" refers to the various ways in which software manages, directs, or influences the operations and behavior of a computer system. This can encompass several areas:

Operating Systems (OS): The OS is fundamental in computer control, managing hardware resources (like CPU, memory, and storage) and providing a user interface. It controls the execution of applications and ensures efficient system operations.

System and Application Software: System software, including utilities and drivers, helps control hardware components and facilitates communication between the OS and peripheral devices. Application software, on the other hand, executes specific tasks or functions, such as word processing or gaming, and relies on system software to interact with the hardware.

Automation Scripts and Programs: Scripts and automation tools can control repetitive tasks or system processes. For example, a script might automate file backups, manage system updates, or configure network settings.

User Interface (UI) Controls: Software applications often include UI elements like buttons, sliders, and menus that allow users to interact with and control the application’s features and functionality.

Remote Control Software: This software allows users to control a computer from a different location, often over a network or the internet. Examples include remote desktop applications and network management tools.

In summary, computer control in software involves managing and directing the operations of both the hardware and applications to ensure they work together effectively and efficiently.