In [1]: print("Hello world!")
Hello world!

In [2]: 2+2
Out[2]: 4

In [3]: _ * 3
Out[3]: 12

In [4]: !ls *.ipynb
notebook1.ipynb  ...

In [5]: %lsmagic
Out[5]: Available line magics:
%alias  %alias_magic  %autocall  %automagic  %autosave  %bookmark  %cd  %clear  %cls  %colors  %config  %connect_info  %copy  %ddir  %debug  %dhist  %dirs  %doctest_mode  %echo  %ed  %edit  %env  %gui  %hist  %history  %install_default_config  %install_ext  %install_profiles  %killbgscripts  %ldir  %less  %load  %load_ext  %loadpy  %logoff  %logon  %logstart  %logstate  %logstop  %ls  %lsmagic  %macro  %magic  %matplotlib  %mkdir  %more  %notebook  %page  %pastebin  %pdb  %pdef  %pdoc  %pfile  %pinfo  %pinfo2  %popd  %pprint  %precision  %profile  %prun  %psearch  %psource  %pushd  %pwd  %pycat  %pylab  %qtconsole  %quickref  %recall  %rehashx  %reload_ext  %ren  %rep  %rerun  %reset  %reset_selective  %rmdir  %run  %save  %sc  %store  %sx  %system  %tb  %time  %timeit  %unalias  %unload_ext  %who  %who_ls  %whos  %xdel  %xmode

Available cell magics:
%%!  %%HTML  %%SVG  %%bash  %%capture  %%cmd  %%debug  %%file  %%html  %%javascript  %%latex  %%perl  %%powershell  %%prun  %%pypy  %%python  %%python3  %%ruby  %%script  %%sh  %%svg  %%sx  %%system  %%time  %%timeit  %%writefile

In [6]: %%writefile test.txt
        Hello world!
Writing test.txt
In [7]: # Let's check what this file contains.
        with open('test.txt', 'r') as f:
            print(f.read())
Hello world!

In [9]: %run?
Type:        Magic function
Namespace:   IPython internal
...
Docstring:
Run the named file inside IPython as a program.
[full documentation of the magic command...]

### New paragraph 
This is *rich* **text** with [links](http://ipython.org),
equations:

$$\hat{f}(\xi) = \int_{-\infty}^{+\infty} f(x)\,
                 \mathrm{e}^{-i \xi x}$$

code with syntax highlighting: 
```python
print("Hello world!")
``` 
and images: 
![This is an image](http://ipython.org/_static/IPy_header.png)

In [11]: from IPython.display import HTML, SVG, YouTubeVideo

In [12]: HTML('''
         <table style="border: 2px solid black;">
         ''' + 
         ''.join(['<tr>' + 
                  ''.join(['<td>{row},{col}</td>'.format(
                                 row=row, col=col
                                 ) for col in range(5)]) +
                  '</tr>' for row in range(5)]) +
         '''
         </table>
         ''')

In [13]: SVG('''<svg width="600" height="80">''' + 
         ''.join(['''<circle cx="{x}" cy="{y}" r="{r}"
                             fill="red"
                             stroke-width="2"
                             stroke="black">
                     </circle>'''.format(x=(30+3*i)*(10-i),
                                         y=30,
                                         r=3.*float(i)
                                         ) for i in range(10)]) + 
         '''</svg>''')

In [14]: YouTubeVideo('j9YpkSX7NNM')

In [15]: from collections import OrderedDict
         from IPython.display import (display,
                                      clear_output,
                                      YouTubeVideo)
         from IPython.html.widgets import DropdownWidget
In [16]: # We create a DropdownWidget, with a dictionary
         # containing the keys (video name) and the values
         # (Youtube identifier) of every menu item.
         dw = DropdownWidget(values=OrderedDict([
                           ('SciPy 2012', 'iwVvqwLDsJo'),
                           ('PyCon 2012', '2G5YTlheCbw'),
                           ('SciPy 2013', 'j9YpkSX7NNM')]
                                                )
                             )
         
         # We create a callback function that displays the 
         # requested Youtube video.
         def on_value_change(name, val):
             clear_output()
             display(YouTubeVideo(val))
         
         # Every time the user selects an item, the 
         # function `on_value_change` is called, and the 
         # `val` argument contains the value of the selected 
         # item.
         dw.on_trait_change(on_value_change, 'value')
         
         # We choose a default value.
         dw.value = dw.values['SciPy 2013']
         
         # Finally, we display the widget.
         display(dw)