virtual environment on python on Ubuntu

 # 1. Update system and install Python tools

sudo apt update && sudo apt install python3-pip python3-venv -y

# 2. Setup Django in a Virtual Environment

mkdir ~/my_project && cd ~/my_project

python3 -m venv venv

source venv/bin/activate

# 3. Install Latest Django

pip install django

django-admin --version

# 4. Verify Ollama is still active

systemctl status ollama --no-pager

# run the server 

python manage.py runserver 0.0.0.0:8000

# on windows 

Then, open http://localhost:8000 on Windows to see the Django rocket!

Example:

root@kayyum-VirtualBox:~/osh# sudo apt install python3-pip python3-venv -y

Reading package lists... Done

Building dependency tree... Done

Reading state information... Done

python3-pip is already the newest version (22.0.2+dfsg-1ubuntu0.7).

The following additional packages will be installed:

  python3-pip-whl python3-setuptools-whl python3.10-venv

The following NEW packages will be installed:

  python3-pip-whl python3-setuptools-whl python3-venv python3.10-venv

0 upgraded, 4 newly installed, 0 to remove and 0 not upgraded.

Need to get 2,479 kB of archives.

After this operation, 2,897 kB of additional disk space will be used.

Get:1 http://in.archive.ubuntu.com/ubuntu jammy-updates/universe amd64 python3-pip-whl all 22.0.2+dfsg-1ubuntu0.7 [1,683 kB]

Get:2 http://in.archive.ubuntu.com/ubuntu jammy-updates/universe amd64 python3-setuptools-whl all 59.6.0-1.2ubuntu0.22.04.3 [789 kB]

Get:3 http://in.archive.ubuntu.com/ubuntu jammy-updates/universe amd64 python3.10-venv amd64 3.10.12-1~22.04.15 [5,714 B]

Get:4 http://in.archive.ubuntu.com/ubuntu jammy-updates/universe amd64 python3-venv amd64 3.10.6-1~22.04.1 [1,042 B]

Fetched 2,479 kB in 4s (707 kB/s)

Selecting previously unselected package python3-pip-whl.

(Reading database ... 216450 files and directories currently installed.)

Preparing to unpack .../python3-pip-whl_22.0.2+dfsg-1ubuntu0.7_all.deb ...

Unpacking python3-pip-whl (22.0.2+dfsg-1ubuntu0.7) ...

Selecting previously unselected package python3-setuptools-whl.

Preparing to unpack .../python3-setuptools-whl_59.6.0-1.2ubuntu0.22.04.3_all.deb ...

Unpacking python3-setuptools-whl (59.6.0-1.2ubuntu0.22.04.3) ...

Selecting previously unselected package python3.10-venv.

Preparing to unpack .../python3.10-venv_3.10.12-1~22.04.15_amd64.deb ...

Unpacking python3.10-venv (3.10.12-1~22.04.15) ...

Selecting previously unselected package python3-venv.

Preparing to unpack .../python3-venv_3.10.6-1~22.04.1_amd64.deb ...

Unpacking python3-venv (3.10.6-1~22.04.1) ...

Setting up python3-setuptools-whl (59.6.0-1.2ubuntu0.22.04.3) ...

Setting up python3-pip-whl (22.0.2+dfsg-1ubuntu0.7) ...

Setting up python3.10-venv (3.10.12-1~22.04.15) ...

Setting up python3-venv (3.10.6-1~22.04.1) ...

root@kayyum-VirtualBox:~/osh# mkdir ~/my_django_project && cd ~/my_django_project

python3 -m venv env

root@kayyum-VirtualBox:~/my_django_project#

root@kayyum-VirtualBox:~/my_django_project#

root@kayyum-VirtualBox:~/my_django_project# python3 -m venv env

root@kayyum-VirtualBox:~/my_django_project# ls

env

root@kayyum-VirtualBox:~/my_django_project# source env/bin/activate

pip install django

Collecting django

  Downloading django-5.2.13-py3-none-any.whl (8.3 MB)

     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 8.3/8.3 MB 3.5 MB/s eta 0:00:00

Collecting asgiref>=3.8.1

  Downloading asgiref-3.11.1-py3-none-any.whl (24 kB)

Collecting sqlparse>=0.3.1

  Downloading sqlparse-0.5.5-py3-none-any.whl (46 kB)

     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 46.1/46.1 KB 611.9 kB/s eta 0:00:00

Collecting typing_extensions>=4

  Downloading typing_extensions-4.15.0-py3-none-any.whl (44 kB)

     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 44.6/44.6 KB 649.0 kB/s eta 0:00:00

Installing collected packages: typing_extensions, sqlparse, asgiref, django

Successfully installed asgiref-3.11.1 django-5.2.13 sqlparse-0.5.5 typing_extensions-4.15.0

(env) root@kayyum-VirtualBox:~/my_django_project#

(env) root@kayyum-VirtualBox:~/my_django_project#

(env) root@kayyum-VirtualBox:~/my_django_project#

(env) root@kayyum-VirtualBox:~/my_django_project# ls

env

(env) root@kayyum-VirtualBox:~/my_django_project#

(env) root@kayyum-VirtualBox:~/my_django_project# ls

env

(env) root@kayyum-VirtualBox:~/my_django_project# rpm -qa | grep django

(env) root@kayyum-VirtualBox:~/my_django_project# pip install djangorestframework django-cors-headers

Collecting djangorestframework

  Downloading djangorestframework-3.17.1-py3-none-any.whl (898 kB)

     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 898.8/898.8 KB 3.2 MB/s eta 0:00:00

Collecting django-cors-headers

  Downloading django_cors_headers-4.9.0-py3-none-any.whl (12 kB)

Requirement already satisfied: django>=4.2 in ./env/lib/python3.10/site-packages (from djangorestframework) (5.2.13)

Requirement already satisfied: asgiref>=3.6 in ./env/lib/python3.10/site-packages (from django-cors-headers) (3.11.1)

Requirement already satisfied: typing_extensions>=4 in ./env/lib/python3.10/site-packages (from asgiref>=3.6->django-cors-headers) (4.15.0)

Requirement already satisfied: sqlparse>=0.3.1 in ./env/lib/python3.10/site-packages (from django>=4.2->djangorestframework) (0.5.5)

Installing collected packages: djangorestframework, django-cors-headers

Successfully installed django-cors-headers-4.9.0 djangorestframework-3.17.1

(env) root@kayyum-VirtualBox:~/my_django_project# pip install djangorestframework django-cors-headers^C

(env) root@kayyum-VirtualBox:~/my_django_project#

Github repo

GITHUB INITIALIZATION OR NEW GITHUB push 

 # ✅ Step 1: Check if Git is installed

git --version

# ✅ Step 2: Configure your Git identity

git config --global user.name "Your Name"

git config --global user.email "youremail@example.com"

# ✅ Step 3: Go to your project directory

cd path/to/your/project

# ✅ Step 4: Initialize git

git init

# ✅ Step 5: Create .gitignore file (optional but recommended)

echo "*.pyc

__pycache__/

.env

venv/

*.sqlite3

" > .gitignore

# ✅ Step 6: Add all files to staging

git add .

# ✅ Step 7: Commit your code

git commit -m "Initial commit"

# ✅ Step 8: Connect to your GitHub repository (replace the URL)

git remote add origin https://github.com/yourusername/your-repo.git

# ✅ Step 9: Rename main branch and push

git branch -M main

git push -u origin main

# ✅ Step 10: Verify connection

git remote -v

----------------------------------------------------------------------------------------

--------------------- Github push failing reason and resolution ---------------

# 🧩 Check Git installation

git --version

# 🧰 Set up Git identity

git config --global user.name "Your Name"

git config --global user.email "youremail@example.com"

# 📂 Move into your project directory

cd path/to/your/project

# 🏗️ Initialize Git if not already done

git init

# 🧾 Create .gitignore (optional but recommended)

echo "*.pyc

__pycache__/

.env

venv/

*.sqlite3

" > .gitignore

# ➕ Add all files to staging

git add .

# 💬 Commit your code

git commit -m "Initial commit"

# 🔗 Set or reset remote repository (replace with your actual repo URL)

git remote remove origin 2> /dev/null

git remote add origin https://github.com/yourusername/your-repo.git

# 🌿 Rename branch to main

git branch -M main

# 🧪 Verify remote

git remote -v

# 🚀 Try pushing your code

git push -u origin main

# 🧱 If push fails due to authentication, generate a Personal Access Token:

#    1. Visit https://github.com/settings/tokens

#    2. Generate new token (classic) with "repo" and "workflow" permissions

#    3. Use your GitHub username, and the token as your password when prompted

# 💾 Save credentials so Git remembers them

git config --global credential.helper store

# 🛠️ If the repo already has commits (like a README), pull first:

git pull origin main --rebase

git push -u origin main

# 🧹 If you still face branch mismatch issues

git branch -M main

git push -u origin main

# 🔒 If switching to SSH (optional)

# git remote set-url origin git@github.com:yourusername/your-repo.git

-----------------------------------------------------------------------------------------

********* SSH SETUp *************************************

# 🧩 Check if SSH is installed

ssh -V

# ✅ Generate a new SSH key (replace with your GitHub email)

ssh-keygen -t ed25519 -C "youremail@example.com"

# When asked for a file path, just press Enter to accept default

# When asked for a passphrase, you can press Enter (optional)

# ✅ Start the SSH agent

eval "$(ssh-agent -s)"

# ✅ Add your private SSH key to the agent

ssh-add ~/.ssh/id_ed25519

# ✅ Show your public key (copy this output)

cat ~/.ssh/id_ed25519.pub

# 🔗 Go to https://github.com/settings/keys

# → Click "New SSH key"

# → Give it a title (e.g., MyLaptop)

# → Paste the copied key

# → Click "Add SSH key"

# ✅ Test SSH connection

ssh -T git@github.com

# ✅ If success: you'll see "Hi username! You've successfully authenticated..."

# 🧰 Now connect your local project with SSH

cd path/to/your/project

# Initialize git if not done already

git init

# Add .gitignore (optional)

echo "*.pyc

__pycache__/

.env

venv/

*.sqlite3

" > .gitignore

# Stage and commit files

git add .

git commit -m "Initial commit"

# ✅ Link your GitHub repo using SSH (replace username/repo)

git remote remove origin 2> /dev/null

git remote add origin git@github.com:yourusername/your-repo.git

# ✅ Push to GitHub

git branch -M main

git push -u origin main

# ✅ Verify remote connection

git remote -v

------------------------------------------------------------------------------

kayyum@DESKTOP-QM3A3JG MINGW64 ~

$ git config --list

diff.astextplain.textconv=astextplain

filter.lfs.clean=git-lfs clean -- %f

filter.lfs.smudge=git-lfs smudge -- %f

filter.lfs.process=git-lfs filter-process

filter.lfs.required=true

http.sslbackend=schannel

core.autocrlf=true

core.fscache=true

core.symlinks=false

pull.rebase=false

credential.helper=manager

credential.https://dev.azure.com.usehttppath=true

init.defaultbranch=master

user.name=Kayyum Shaikh

user.email=kayyum****@gmail.com

-------------------------------------------------------------------------------

Python Errors and Meaning

Pro Tips to Spot Errors Quickly

• ValueError → "The value you gave is wrong" ✅ → Right type, wrong data

• IndexError → "The position you're trying to reach doesn’t exist" ❌

• TypeError → "You're mixing incompatible types" ⚡

• NameError → "That variable doesn’t exist" 🔍

• SyntaxError → "Python can’t even read this code" 🛑

-------------------------------------------------------------------------------------------------------------------

Error Type ---------------	Meaning --------------------	Cause -------------------------	Example ------------------------	How to Spot / Fix -----------------------
SyntaxError	Invalid code structure	Python cannot parse your code	print "Hello"	Check for missing colons, parentheses, quotes
IndentationError	Wrong indentation level	Misaligned spaces/tabs	if True:\nprint("Hi")	Always use consistent indentation (4 spaces)
NameError	Variable not defined	Using a variable before declaring it	print(x)	Define the variable before use
TypeError	Incompatible types	Performing invalid operations between data types	"5" + 5	Convert types explicitly: int("5") + 5
ValueError	Invalid value for the operation	Correct type but unacceptable value	int("abc")	Ensure input values are valid
IndexError	Index out of range	Accessing an invalid list/tuple index	[1,2,3][5]	Check list length before accessing
KeyError	Missing dictionary key	Accessing a non-existent key	{"a":1}["b"]	Use .get() or check with in
ZeroDivisionError	Division by zero	Dividing a number by zero	10/0	Check denominator before division
AttributeError	Invalid attribute access	Using a method or property that doesn't exist	"abc".push()	Use dir(obj) to see valid attributes
ImportError	Module not found	Importing a non-existent or misplaced module	import mymodule (not present)	Check module name and path
ModuleNotFoundError	Subclass of ImportError	Specific case when the module cannot be located	import unknownlib	Install or correct module
RuntimeError	Error that occurs at runtime	General unexpected errors	Rare and contextual	Check traceback for details
AssertionError	Failed assert statement	When the assertion condition is false	assert 2+2==5	Validate assumptions
OverflowError	Number too large for calculation	Exceeding numeric limits	math.exp(1000)	Use decimal or fractions module
MemoryError	Not enough memory	Processing huge datasets	Creating a massive list	Optimize memory usage
EOFError	Input ends unexpectedly	Calling input() but no data provided	input() without data	Ensure valid user input
OSError	System-related errors	Issues like missing files, permissions, etc.	open("nofile.txt")	Check file paths and permissions

--------------------------------------------------------------------------------------------------------------------

singly linked list advanced

 class Node:
  def __init__(self,data):
    self.data = data 
    self.next = None 
class sl:
  def __init__(self):
    self.head = None 
  
  def is_empty(self):
    return self.head is None 
  
  def insert(self,value):
    new_node = Node(value)
    if self.is_empty():
      self.head = new_node
    else:
      new_node.next = self.head 
      self.head = new_node
  
  def insert_at(self,value,new_value):
    new_node = Node(new_value)
    current = self.head 
    while current:
      if current.data == value:
        new_node.next = current.next 
        current.next = new_node
      current = current.next 
    print()
  
  def show(self):
    current = self.head 
    while current:
      print(current.data,'->',end='')
      current = current.next 
    print()
  
  def delete(self,value):
    current = self.head 
    
    if current.data == value:
      self.head.data = None 
      self.head = self.head.next
    while current:
      if current.data == value and current.next != None:
        current.data = current.next.data 
        current.next = current.next.next 
      current = current.next 
    l.show()
    print()
    
l = sl()
for i in range(1,10):
  l.insert(i)
  
l.show()
l.delete(9)
l.delete(1)
l.delete(8)
l.delete(7)
l.delete(6)
l.delete(3)
l.delete(2)

Output:

9 ->8 ->7 ->6 ->5 ->4 ->3 ->2 ->1 ->
8 ->7 ->6 ->5 ->4 ->3 ->2 ->1 ->

8 ->7 ->6 ->5 ->4 ->3 ->2 ->1 ->

7 ->6 ->5 ->4 ->3 ->2 ->1 ->

6 ->5 ->4 ->3 ->2 ->1 ->

5 ->4 ->3 ->2 ->1 ->

5 ->4 ->2 ->1 ->

5 ->4 ->1 ->

Circular Linked List Python

# python circular linked list

class Node:

  def __init__(self,data):

    self.data = data

    self.next = None

class cl:

  def __init__(self):

    self.head = None

 

  def is_empty(self):

    return self.head is None

 

  def insert(self,value):

    new_node = Node(value)

    if self.is_empty():

      self.head = new_node

      new_node.next = self.head

    else:

      current = self.head

      while current.next != self.head :

        current = current.next

      current.next = new_node

      new_node.next = self.head

      self.head = new_node

 

  def display(self):

    current = self.head

    while current.next != self.head :

      print(current.data,'<->',end='')

      current = current.next

    print()

   

  def delete(self,value):

    current = self.head

    while current.next != self.head:

      if current.data == value:

        current.data = None

        current.data = current.next.data

        current.next = current.next.next

      current = current.next

    print("deleted.")

    self.display()

   

  def update(self,value,alternate):

    current = self.head

    while current.next != self.head:

      if current.data == value:

        current.data = alternate

      current = current.next

    print("updated.")

    self.display()

 

  def size(self):

    current = self.head

    size=0

    while current.next != self.head:

      size+=1

      current = current.next

    print(f"size of circular linked list: \n{size}")

   

l = cl()

for i in range(10):

  l.insert(i)

l.display()

l.delete(5)

l.insert(55)

l.display()

l.delete(1)

l.update(6,66)

l.size()

-----------------------------------------------------

output:

-----------------------------------------------------

9 <->8 <->7 <->6 <->5 <->4 <->3 <->2 <->1 <-> deleted. 9 <->8 <->7 <->6 <->4 <->3 <->2 <->1 <-> 55 <->9 <->8 <->7 <->6 <->4 <->3 <->2 <->1 <-> deleted. 55 <->9 <->8 <->7 <->6 <->4 <->3 <->2 <-> updated. 55 <->9 <->8 <->7 <->66 <->4 <->3 <->2 <-> size of circular linked list: 8

------------------------------------------------------

Doubly Linked List Python

 

# singly linked list

class Node:

  def __init__(self,data):

    self.data = data

    self.prev = None

    self.next = None

class dl:

  def __init__(self):

    self.head = None

    self.tail = None

 

  def is_empty(self):

    return self.head is None

 

  def insertb(self,value):

    new_node = Node(value)

    if self.is_empty():

      self.head = self.tail = new_node

    else:

      new_node.next = self.head

      self.head.prev = new_node

      self.head = new_node

 

  def inserte(self,value):

    new_node = Node(value)

    if self.is_empty():

      self.head = self.tail = new_node

    else:

      new_node.prev = self.tail

      self.tail.next = new_node

      self.tail = new_node

 

  def forward(self):

    current = self.head

    while current:

      if current.data != None:

        print(current.data,'<->',end='')

      current = current.next

    print()

  def backward(self):

    current = self.tail

    while current:

      if current.data != None:

        print(current.data,'<->',end='')

      current = current.prev

    print()

  def delete(self,value):

    current = self.head

    while current:

      if current.data != None and current.data == value:

        current.data = None

      current = current.next

    print("deleted...")

    self.forward()

    self.backward()

    self.size()

 

  def update(self,value,replace):

    current = self.head

    while current:

      if current.data != None and current.data == value:

        current.data = replace

      current = current.next

    print("updated...")

    self.forward()

    self.backward()

   

  def size(self):

    current = self.head

    size=0

    while current:

      if current.data != None :

        size += 1

      current = current.next

    print(f"size is {size}...!")

 

l = dl()

l.insertb(1)

l.insertb(2)

l.insertb(3)

l.inserte(4)

l.inserte(5)

l.delete(1)

l.update(2,22)

Singly linked list python

 

# singly linked list

class Node:

  def __init__(self,data):

    self.data = data

    self.next = None

class ll:

  def __init__(self):

    self.head = None

 

  def is_empty(self):

    return self.head is None

 

  def insert(self,value):

    new_node = Node(value)

    if self.is_empty():

      self.head = new_node

    else:

      new_node.next = self.head

      self.head = new_node

 

  def show(self):

    current = self.head

    while current:

      if current.data != None:

        print(current.data,'->',end='')

      current = current.next

    print()

 

  def delete(self,value):

    current = self.head

    while current:

      if current.data != None and current.data == value:

        current.data = None

      current = current.next

    print("deleted...")

    self.show()

    self.size()

# if you wish to delete the node and don't want none

    def delete(self,value):

        current = self.head

        while current:

            if current.data == value:

                previous.next = current.next  # Skip over the node to delete it

                current = None  # Optional: free the node

                print(f"Node with value {value} deleted.")

                self.display()

                return

            previous = current

            current = current.next

 

  def update(self,value,replace):

    current = self.head

    while current:

      if current.data != None and current.data == value:

        current.data = replace

      current = current.next

    print("updated...")

    self.show()

   

  def size(self):

    current = self.head

    size=0

    while current:

      if current.data != None :

        size += 1

      current = current.next

    print(f"size is {size}...!")

 

l = ll()

l.insert(1)

l.insert(2)

l.insert(3)

l.insert(4)

l.insert(5)

l.show()