sitc/python/1_4_Sets.ipynb

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    "![](http://www.upm.es/sfs/Rectorado/Gabinete%20del%20Rector/Logos/UPM/EscPolitecnica/EscUpmPolit_p.gif \"UPM\")"
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   "source": [
    "# Course Notes for Learning Intelligent Systems"
   ]
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  {
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   "metadata": {},
   "source": [
    "Department of Telematic Engineering Systems, Universidad Politécnica de Madrid, © Carlos A. Iglesias"
   ]
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  {
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   "source": [
    "# Built-in Types: Sets and Mappings"
   ]
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   "source": [
    "* *Sets* are unordered bags of values\n",
    "* *Dictionaries* are unordered bags of key-values pairs\n",
    "\n",
    "A set object is an unordered collection of distinct objects. There are two built-in set types: **set** (mutable) and **frozenset** (inmutable).\n",
    "\n",
    "A mapping object maps hashable values to arbitrary objects. Mappings are mutable objects. There is only one builtin mapping type: **dictionary**."
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   "source": [
    "## 1. Sets"
   ]
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   "outputs": [],
   "source": [
    "my_set = set() #create a set\n",
    "my_set"
   ]
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   "cell_type": "code",
   "execution_count": null,
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   "outputs": [],
   "source": [
    "my_set.add(1) # add an element\n",
    "my_set"
   ]
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  {
   "cell_type": "code",
   "execution_count": null,
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   "outputs": [],
   "source": [
    "my_set.add(2) # add another element"
   ]
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   "cell_type": "code",
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   "outputs": [],
   "source": [
    "my_set"
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  {
   "cell_type": "code",
   "execution_count": null,
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   "source": [
    "my_set.add(3) # add another one\n",
    "my_set"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "my_set.add(1) #try to add a repeated element\n",
    "my_set"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "s2 = set(range(10)) # we can create a set from a range\n",
    "s2"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "l = ['a', 'a', 'b', 'c', 'c', 'c']"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "s3 = set(l) # if we create a set from a list, elements are not repeated\n",
    "s3"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "len(s3) "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
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   "outputs": [],
   "source": [
    "s3.union(s2) # we can use set methods: union(), intersection(), difference(), ..."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "3 in my_set #check membership"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "type(s3)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 2. Dictionaries"
   ]
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  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "my_dictionary = {'key1': 1, 'key2': 2, 'key3': 3} # pairs of key-value mappings\n",
    "my_dictionary"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "my_dictionary['key1'] #retrieve a value given a key"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "my_dict = dict()\n",
    "my_dict['key1'] = 1\n",
    "my_dict['key2'] = 2\n",
    "my_dict['key3'] = 3\n",
    "my_dict # alternative way to create a dictionary "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "my_dict == my_dictionary # check if both dictionaries are equal"
   ]
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  {
   "cell_type": "code",
   "execution_count": null,
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   "outputs": [],
   "source": [
    "my_dict2 = {'one': {'two': {'three': 'Nested dict'}}} #nested dictionary\n",
    "my_dict2"
   ]
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   "cell_type": "code",
   "execution_count": null,
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   "outputs": [],
   "source": [
    "my_dict2['one']['two']['three'] #access the value"
   ]
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  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Dictionaries have different methods, check them with Tab."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "my_dict.keys() # in Python3 we get a View object that changes when the dictionary changes"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "list(my_dict.keys()) # we can convert it to a list, we see dicionaries are unordered"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "my_dict.values()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "list(my_dict.values())"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "type(my_dict)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Licence"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The notebook is freely licensed under under the [Creative Commons Attribution Share-Alike license](https://creativecommons.org/licenses/by/2.0/).  \n",
    "\n",
    "© Carlos A. Iglesias, Universidad Politécnica de Madrid."
   ]
  }
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