# Python Jupyter Notebooks

Jupyter Notebook is an open-source web application that allows you to create and share documents that contain live code, equations, visualizations, and narrative text. It is a standard tool in data science and machine learning.

## Installation

```bash
pip install notebook
```

## Starting the Notebook

To start the notebook server, run the following command in your terminal. This will open the dashboard in your default web browser.

```bash
jupyter notebook
```

## Cell Types

Notebooks consist of a sequence of cells.

*   **Code Cells**: Contain code to be executed. The output is displayed immediately below the cell.
*   **Markdown Cells**: Contain text formatted using Markdown (like this note). Used for documentation and narrative.

## Magic Commands

Magic commands are special commands that start with `%` (line magic) or `%%` (cell magic).

### Common Magics

*   `%timeit`: Times the execution of a Python statement or expression.
*   `%%time`: Times the execution of the entire cell.
*   `%who`: Lists all variables in the global scope.
*   `%matplotlib inline`: Ensures matplotlib plots are displayed inline within the notebook.
*   `!`: Runs a shell command (e.g., `!pip install pandas`).

```python
# Example of magic command
%timeit [x**2 for x in range(1000)]
```

## Keyboard Shortcuts

There are two modes: **Edit mode** (press `Enter` to enable) and **Command mode** (press `Esc` to enable).

### Command Mode (Esc)

*   `A`: Insert cell above.
*   `B`: Insert cell below.
*   `M`: Change cell to Markdown.
*   `Y`: Change cell to Code.
*   `D, D` (press D twice): Delete selected cell.
*   `Shift + Enter`: Run cell and select next.
*   `Ctrl + Enter`: Run cell and stay selected.

## Kernel

The kernel is the computational engine that executes the code contained in a notebook document.

*   **Interrupt**: Stops the execution of the current cell.
*   **Restart**: Restarts the kernel and clears all variables.

## Exporting

Notebooks (`.ipynb`) can be exported to various formats including HTML, PDF, and Python scripts (`.py`).

[[programming/python/python]]