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‎advanced/collections.md

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# Handy classes in the standard library
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So far we have learned to use lists, tuples and dictionaries. They are
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commonly used data types in Python. The standard library contains more
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handy types that behave a lot like the datatypes that we know already.
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You can always use the built-in types instead of the collections module,
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but sometimes the collections module makes everything a lot easier.
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## Sets
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Let's say we have two lists of strings
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```python
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```
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## Named tuples
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It can be tempting to make a class that just contains a bunch of data
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and that's it.
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```python
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class Website:
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def __init__(self, url, founding_year, free_to_use):
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self.url = url
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self.founding_year = founding_year
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self.free_to_use = free_to_use
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github = Website('https://github.com/', 2008, True)
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```
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You should avoid making classes like this. This class has only one
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method, so it doesn't really need to be a class. We could just use a
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tuple instead:
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```python
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github = ('https://github.com/', 2008, True)
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```
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The problem with this is that if someone reading our code sees something
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like `website[1] > 2010` it's not going to make much sense, like
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`website.founding_year > 2010` would.
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In cases like this, `collections.namedtuple` is handy:
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```python
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>>> Website = collections.namedtuple('Website', 'url founding_year free_to_use')
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>>> github = Website('https://github.com/', 2008, True)
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>>> github[1]
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2008
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>>> for thing in github:
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... print(thing)
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...
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https://github.com/
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2008
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True
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>>> github.founding_year
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2008
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>>> github
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Website(url='https://github.com/', founding_year=2008, free_to_use=True)
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>>> print(github)
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Website(url='https://github.com/', founding_year=2008, free_to_use=True)
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>>>
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```
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As you can see, our `github` behaves like a tuple, but
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`github.founding_year` also works and `github` looks nice when we have a
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look at it on the `>>>` prompt or we print it.
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## Deques
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To understand deques, we need to first learn about a list method I
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haven't talked about earlier. It's called `pop` and it works like this:
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```python
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>>> names = ['wub_wub', 'theelous3', 'Nitori', 'RubyPinch', 'go|dfish']
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>>> names.pop()
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'go|dfish'
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>>> names
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['wub_wub', 'theelous3', 'Nitori', 'RubyPinch']
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>>> names.pop()
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'RubyPinch'
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>>> names
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['wub_wub', 'theelous3', 'Nitori']
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>>> names.pop()
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'Nitori'
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>>> names
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['wub_wub', 'theelous3']
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```
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As you can see, the list shortens by one from the end when we pop from
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it, and we also get the removed value back. So now we know that we can
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add an item to the end of a list using `append`, and we can remove an
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item from the end using `pop`.
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It's also possible to do this in the beginning of a list, but lists were
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not designed to be used that way and it would be slow if our list would
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be big.
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The `collections.deque` class makes appending and popping from both ends
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easy and fast. It works just like lists, but it also has `appendleft`
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and `popleft` methods.
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```python
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>>> names = collections.deque(['theelous3', 'Nitori', 'RubyPinch'])
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>>> names
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deque(['theelous3', 'Nitori', 'RubyPinch'])
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>>> names.appendleft('wub_wub')
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>>> names.append('go|dfish')
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>>> names
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deque(['wub_wub', 'theelous3', 'Nitori', 'RubyPinch', 'go|dfish'])
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>>> names.popleft()
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'wub_wub'
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>>> names.pop()
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'go|dfish'
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>>> names
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deque(['theelous3', 'Nitori', 'RubyPinch'])
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>>>
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```
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Deques are often used as queues. It means that items are always added to
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one end and popped from the other end.
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**TODO:** add some of ChainMap, Counter, OrderedDict, defaultdict, deque, sets

‎basics/what-is-programming.md

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languages consist of English words, digits and some characters that have
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special meanings.
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Unlike people often think, **programming is not complicated**. Large
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programs are always made of small, simple pieces, and those pieces are
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written one by one. Programming languages are made to be used by humans,
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so if there's an easy way to do something and a difficult way to do
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something, you should use the easier way.
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Unlike people often think, programming is usually not complicated. Large
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programs are always made of **small, simple pieces**, and those pieces
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are written one by one. Programming languages are made to be used by
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humans, so if there's an easy way to do something and a difficult way to
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do something, you should use the easier way.
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## What do I need?
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programming on a 12-year-old computer if I needed to. Fast computers are
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nice to work with, but you don't need them.
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Programming takes time like all hobbies do. Some people learn it
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quickly, and some people don't. I don't expect you to read this tutorial
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in a couple hours and then master everything it's talking about. Take
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your time with things, and remember that I learned to program slowly.
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Programming takes time like all hobbies do. Some people learn it
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quickly, and some people don't. I don't expect you to read this tutorial
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in a couple hours and then master everything it's talking about. Take
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your time with things, and remember that I learned to program slowly.
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## Getting started
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2. Read the code and the explanation for it again.
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3. If there's something you haven't seen before in the tutorial and it's
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not explained, try to find it from the previous chapters.
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4. If you still have trouble understanding the tutorial or any other problems
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with the tutorial, please [tell me about it](../contact-me.md). I want to
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improve this tutorial so other readers won't have the same problem as you
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have.
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4. If you can't find what you're looking for or you still have trouble
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understanding the tutorial or any other problems with the tutorial,
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please [tell me about it](../contact-me.md). I want to improve this
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tutorial so other readers won't have the same problem as you have.
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5. See [Getting help](../getting-help.md) if you can't contact me for some
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reason.
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