# Python Installation - Ubuntu/Debian

## Check Current Version

```bash
python3 --version
```

If you see Python 3.11+, you're good to go! [← Back to main skill](../SKILL.md#step-2-create-virtual-environment)

---

## Installation Methods

### Option 1: From Ubuntu PPA (Recommended for Latest Versions)

**For Python 3.13 (latest):**

```bash
sudo apt update
sudo apt install software-properties-common -y
sudo add-apt-repository ppa:deadsnakes/ppa -y
sudo apt update
sudo apt install python3.13 python3.13-venv python3.13-dev -y
```

**For Python 3.11:**

```bash
sudo apt update
sudo apt install software-properties-common -y
sudo add-apt-repository ppa:deadsnakes/ppa -y
sudo apt update
sudo apt install python3.11 python3.11-venv python3.11-dev -y
```

**Verify installation:**
```bash
python3.13 --version
```

---

### Option 2: System Package Manager (Older Versions)

**Ubuntu 22.04+ includes Python 3.10+ by default:**

```bash
sudo apt update
sudo apt install python3 python3-venv python3-pip python3-dev -y
```

**Check version:**
```bash
python3 --version
```

---

### Option 3: pyenv (Multiple Versions)

**Install dependencies:**
```bash
sudo apt update
sudo apt install -y make build-essential libssl-dev zlib1g-dev \
  libbz2-dev libreadline-dev libsqlite3-dev wget curl llvm \
  libncursesw5-dev xz-utils tk-dev libxml2-dev libxmlsec1-dev \
  libffi-dev liblzma-dev
```

**Install pyenv:**
```bash
curl https://pyenv.run | bash
```

**Add to ~/.bashrc or ~/.zshrc:**
```bash
export PYENV_ROOT="$HOME/.pyenv"
export PATH="$PYENV_ROOT/bin:$PATH"
eval "$(pyenv init --path)"
eval "$(pyenv init -)"
```

**Reload shell:**
```bash
source ~/.bashrc  # or source ~/.zshrc
```

**Install Python 3.13:**
```bash
pyenv install 3.13.0
pyenv global 3.13.0
```

**Verify:**
```bash
python --version
```

---

## Set Default Python Version

**If you installed Python 3.13 but `python3` still points to old version:**

```bash
sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.13 1
sudo update-alternatives --config python3
```

**Select the number for Python 3.13**

---

## Install pip

**For Python 3.13:**
```bash
sudo apt install python3.13-distutils -y
curl -sS https://bootstrap.pypa.io/get-pip.py | python3.13
```

**Or use system package:**
```bash
sudo apt install python3-pip -y
```

**Verify:**
```bash
python3 -m pip --version
```

---

## Troubleshooting

### Issue: `E: Unable to locate package python3.13`

**Solution:** Add deadsnakes PPA (see Option 1 above)

### Issue: `No module named 'venv'`

**Install venv module:**
```bash
sudo apt install python3.13-venv -y
```

### Issue: `No module named 'distutils'`

**Install distutils:**
```bash
sudo apt install python3.13-distutils -y
```

### Issue: Build dependencies missing (for pyenv)

**Install build essentials:**
```bash
sudo apt install build-essential libssl-dev zlib1g-dev \
  libbz2-dev libreadline-dev libsqlite3-dev curl \
  libncursesw5-dev xz-utils tk-dev libffi-dev liblzma-dev -y
```

### Issue: Permission denied when installing packages

**Don't use sudo with pip!** Use virtual environments instead:
```bash
python3 -m venv venv
source venv/bin/activate
pip install <package>
```

---

## Verification Checklist

- [ ] `python3 --version` shows 3.11+
- [ ] `python3 -m venv --help` shows venv usage
- [ ] `python3 -m pip --version` works
- [ ] Can create test venv: `python3 -m venv test_venv`
- [ ] Can activate: `source test_venv/bin/activate`

**Clean up test:**
```bash
rm -rf test_venv
```

---

[← Back to django-project-setup](../SKILL.md)