mirror of
https://github.com/gsi-upm/sitc
synced 2024-11-16 11:32:28 +00:00
322 lines
7.2 KiB
Plaintext
322 lines
7.2 KiB
Plaintext
{
|
|
"cells": [
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"![](http://www.upm.es/sfs/Rectorado/Gabinete%20del%20Rector/Logos/UPM/EscPolitecnica/EscUpmPolit_p.gif \"UPM\")"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"# Course Notes for Learning Intelligent Systems"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"Department of Telematic Engineering Systems, Universidad Politécnica de Madrid, © Carlos A. Iglesias"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"# Variables"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"## 1. Strongly typed and dynamically typed"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"As we have seen previously, in Python we can assign an object to a variable with the assignment operator (=).\n",
|
|
"\n",
|
|
"Binding a variable in Python means setting a name to hold a reference to some object. Assignment creates references, not copies.\n",
|
|
"\n",
|
|
"Names in Python do not have an intrinsic type. Objects have types. Python determines the type of the reference automatically based on the data object assigned to it.\n",
|
|
"\n",
|
|
"In Python, everything is an object, there no difference between primitive types, functions and objects: all are objects."
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"a = 2\n",
|
|
"a"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"Python is a **strongly typed** language and **dynamically typed** language.\n",
|
|
"\n",
|
|
"This means:\n",
|
|
"* **dynamically typed**: variables do not declare a static type (as in Java int a = 2;). Variables have no type themselves, they are just names that hold a reference to some object. The type of the variable is changed dynamically when you change the type of the assigned data object. \n",
|
|
"* **strongly typed**: the interpreter tracks variable types. There is no implicit type conversion. This means that all the type variables should be converted manually, preventing from unexpected behaviour. "
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"type(a)"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"## Exercises"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"Can we assign a String value to the variable a? \n",
|
|
"Can we assign the expression 'd' + 3 to the variable a?\n",
|
|
"\n",
|
|
"\n",
|
|
"Give reasons for your answers and check them below."
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"a = 'd'\n",
|
|
"a"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"a = 'd' + 3\n",
|
|
"a"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"## 2. Mutability"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"Objects whose value can change are said to be **mutable**; objects whose value is unchangeable once they are created are called **immutable**.\n",
|
|
"\n",
|
|
"* **Mutable types**: integers, floats, strings, lists, set\n",
|
|
"* **Inmutable types**: tuples, ranges, dictionaries"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"# Exercise mutable type\n",
|
|
"a = 10\n",
|
|
"b = a\n",
|
|
"b = 5\n",
|
|
"print('a', a)\n",
|
|
"print('b', b)\n",
|
|
"\n",
|
|
"# Which will be the values of a and b?"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"# Exercise mutable type\n",
|
|
"a = 10\n",
|
|
"a = 10 + 1\n",
|
|
"print(a)\n",
|
|
"\n",
|
|
"# Can we change 'a' if it is inmutable?"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"# Exercise mutable type\n",
|
|
"a = \"Hola\"\n",
|
|
"b = a\n",
|
|
"b = \"Hi\"\n",
|
|
"print('a', a)\n",
|
|
"print('b', b)\n",
|
|
"\n",
|
|
"# Which will be the values of a and b?"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"# Exercise mutable type\n",
|
|
"a = [1, 2, 3]\n",
|
|
"b = a\n",
|
|
"a.append(4)\n",
|
|
"print('a', a)\n",
|
|
"print('b', b)\n",
|
|
"\n",
|
|
"# Which will be the value of a and b?"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"## 3. Scope"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"# Example of a local variable\n",
|
|
"# The scope defines the visibility of a name within a block. \n",
|
|
"# If a local variable is defined in a block, its scope includes that block. \n",
|
|
"\n",
|
|
"c = 3\n",
|
|
"def add(a, b):\n",
|
|
" c = a + b\n",
|
|
" return c\n",
|
|
"d = add(2, 2)\n",
|
|
"print('d', d)\n",
|
|
"print('c', c)"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"# Access global variables\n",
|
|
"\n",
|
|
"c = 3\n",
|
|
"def add(a, b):\n",
|
|
" global c\n",
|
|
" c = a + b\n",
|
|
" return c\n",
|
|
"d = add(2, 2)\n",
|
|
"print('d', d)\n",
|
|
"print('c', c)"
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "markdown",
|
|
"metadata": {},
|
|
"source": [
|
|
"## 4. Constants\n",
|
|
"\n",
|
|
"In Python there is no way to specify that a variable is constant, but there is the convention to write their names in all caps, with underscores separating words."
|
|
]
|
|
},
|
|
{
|
|
"cell_type": "code",
|
|
"execution_count": null,
|
|
"metadata": {},
|
|
"outputs": [],
|
|
"source": [
|
|
"NUMBER_OF_LIFES = 5\n",
|
|
"\n",
|
|
"print(NUMBER_OF_LIFES)\n",
|
|
"\n",
|
|
"# built-in constants usually do no follow the convention \n",
|
|
"import math\n",
|
|
"print(math.pi)\n"
|
|
]
|
|
},
|
|
{
|
|
"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."
|
|
]
|
|
}
|
|
],
|
|
"metadata": {
|
|
"kernelspec": {
|
|
"display_name": "Python 3",
|
|
"language": "python",
|
|
"name": "python3"
|
|
},
|
|
"language_info": {
|
|
"codemirror_mode": {
|
|
"name": "ipython",
|
|
"version": 3
|
|
},
|
|
"file_extension": ".py",
|
|
"mimetype": "text/x-python",
|
|
"name": "python",
|
|
"nbconvert_exporter": "python",
|
|
"pygments_lexer": "ipython3",
|
|
"version": "3.7.1"
|
|
},
|
|
"latex_envs": {
|
|
"LaTeX_envs_menu_present": true,
|
|
"autocomplete": true,
|
|
"bibliofile": "biblio.bib",
|
|
"cite_by": "apalike",
|
|
"current_citInitial": 1,
|
|
"eqLabelWithNumbers": true,
|
|
"eqNumInitial": 1,
|
|
"hotkeys": {
|
|
"equation": "Ctrl-E",
|
|
"itemize": "Ctrl-I"
|
|
},
|
|
"labels_anchors": false,
|
|
"latex_user_defs": false,
|
|
"report_style_numbering": false,
|
|
"user_envs_cfg": false
|
|
}
|
|
},
|
|
"nbformat": 4,
|
|
"nbformat_minor": 1
|
|
}
|