# Life is Like A Python List

Life is like a Python list. You spend most of it in boxes. Sometimes the box is empty and sometimes the box is filled with different objects. And sometimes it’s a box within a box. I like to think of Python lists as boxes because the brackets look like a container. We make an empty box, or list, like this:

1 2 | >>> [] [] |

But that’s not very useful. Let’s give it a name:

1 2 3 | >>> box = [] >>> box [] |

Some chocolates ship with a map displaying the type and location of chocolates within the box. This is our *index. *Let’s say I just picked up a box of Whizzo Chocolates. In Python, it would look like this:

1 2 3 4 5 6 | >>> whizzo = ['Cherry Fondue', 'Crunchy Frog', 'Ram\'s Bladder Cup', 'Cockroach Cluster', 'Anthrax Ripple', 'Spring Surprise'] |

The chocolate I want is ‘Crunchy Frog’. I access that delectable item by its index, like so:

1 2 | >>> whizzo[1] 'Crunchy Frog' |

Remember our discussion on counting in Strings? It works the same with Lists. We always start at 0. Here’s a quick refresher.

1 2 3 | >>> t = [1,2,3] >>> t[1] 2 |

I named this example list **t. **It’s a convention you will encounter frequently. Why t? Because **list** is a keyword and **l** looks too much like 1 or I.

We can assign list items to variables, like this:

1 2 3 | >>> dessert = whizzo[1] >>> dessert 'Crunchy Frog' |

Or, to clarify the counting, look at it like this:

1 2 3 4 | >>> t = [1, 2, 3] >>> two = t[1] >>> two 2 |

Try it with the other indices.

As long as the value is an integer, we can use a variable as an index to access an item. Let me pick a chocolate for you, at random:

1 2 3 | >>> from random import randint >>> i = randint(0, len(whizzo)-1) >>> whizzo[i] |

Delicious, no? Life is like a box of Whizzo chocolates. You never know what you’re going to get.

## Heterogeneity & Mutability & Nesting & What?

Unlike strings, lists are mutable. We can modify a list item through its index.

1 2 3 4 | >>> t = [1,2,3] >>> t[2] = "three" >>> t [1,2,'three'] |

Did you see what I did there? I swapped the value of 3 with the string ‘three’. Lists are *heterogeneous*, which means “composed of parts of different kinds”. Lists can contain any type of object, even other lists.

1 2 3 4 5 | >>> t [1,2,'three'] >>> t[2] = [4,5,6] >>> t [1, 2, [4, 5, 6]] |

Here’s one more example:

1 2 3 4 5 | >>> a = [1,2,3] >>> b = [4,5,6] >>> c = [a,b] >>> c [[1, 2, 3], [4, 5, 6]] |

Get your hands dirty in our next tutorial on list concatenation, multiplication, and slicing.