===================
Extra Code Samples
===================

Basic list operations
=====================

You're going to enjoy lists.

.. sourcecode:: python

    >>> my_list = [1, 2, 3]
    >>> my_list.append(4)
    >>> my_list
    [1, 2, 3, 4]
    >>> my_list.insert(2, 'dog')
    >>> my_list
    [1, 2, 'dog', 3, 4]
    >>> my_list.extend([5, 6])
    >>> my_list
    [1, 2, 'dog', 3, 4, 5, 6]
    >>> my_list.append([7, 8])
    >>> my_list
    [1, 2, 'dog', 3, 4, 5, 6, [7, 8]]
    >>> my_list.pop(2)
    'dog'
    >>> my_list
    [1, 2, 3, 4, 5, 6, [7, 8]]
    >>> my_list.reverse()
    >>> my_list
    [[7, 8], 6, 5, 4, 3, 2, 1]

Lists + functional programming
==============================

.. sourcecode:: python

    >>> def divisible_by_2(x):
    ...    return x % 2 == 0
    ...    
    >>>
    >>> def cube(x):
    ...    return x ** 3
    ...        
    >>>
    >>> numbers = [1, 2, 3, 4, 6, 31]
    >>>
    >>> filter(divisible_by_2, numbers)
    >>> [2, 4, 6]
    >>>
    >>> map(cube, numbers)
    >>> [1, 8, 27, 64, 216, 29791]

Generators
==========

.. sourcecode:: python

    def print_5_lines(filename):
        """ Prints the first 5 lines of the given file. """
        my_file = open(filename)    # my_file is a generator expression
        for i in range(5):
            line = my_file.next()
            print line

This is useful for gigantic files, such as 100MB system logs.

Filesystem tools
================

List all the .log files in a directory, including all subdirectories.

.. sourcecode:: python

    import os
    import os.path

    for dirpath, dirnames, filenames in os.walk("."):
        for filename in [f for f in filenames if f.endswith(".log")]:
            print os.path.join(dirpath, filename)

Code taken from http://stackoverflow.com/questions/954504/how-to-get-files-in-a-directory-including-all-subdirectories

Dealing with tarfiles
=====================

Open and read nested tarfiles, without having to write the extracted files to disk.

.. sourcecode:: python

    >>> import tarfile
    >>> baz = tarfile.open('baz.tgz')
    >>> bar = tarfile.open(fileobj=baz.extractfile('bar.tgz'))
    >>> bar.extractfile('bar/baz.txt').read()
    'This is bar/baz.txt.\n'

From http://stackoverflow.com/questions/3293809/how-to-walk-a-tar-gz-file-that-contains-zip-files-without-extraction