Notebooks/Python_Basic/04_Scopes.ipynb

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    "# Introduction to Python  \n",
    "\n",
    "## Scopes\n",
    "\n",
    "### Scopes are defined after a colon (:) and are delimited by the indentation. "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "< scope creation statement>:  \n",
    ".... command  \n",
    ".... command  \n",
    ".... command  \n",
    ".... command  \n",
    "< end of scope>  "
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Scopes are created after the following primitives:  \n",
    "+ _if_  \n",
    "+ _for_  \n",
    "+ _while_  \n",
    "+ _def_  \n",
    "+ _class_  \n",
    "+ _with_  \n",
    "\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "***"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Nested Scopes in Python"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
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     "text": [
      "local2\n",
      "local1\n",
      "global\n"
     ]
    }
   ],
   "source": [
    "x = 'global'\n",
    "\n",
    "def local1():     #If another variable exists with the same name inside the function, the reference before assignment yields an error\n",
    "    #print(x)\n",
    "    x = 'local1'\n",
    "    def local2():\n",
    "        #print(x)\n",
    "        x = 'local2'\n",
    "        print(x)\n",
    "    local2()   \n",
    "    print(x)\n",
    "\n",
    "local1()\n",
    "print(x)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "***"
   ]
  },
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   "metadata": {},
   "source": [
    "### Variables and Functions defined in the inner scope:"
   ]
  },
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    {
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     "text": [
      "What's your name: My_name is Renato\n",
      "What's your name: My name is Pedro\n",
      "What's your name: My name is Pedro\n",
      "What's your name: My_name is Renato\n",
      "What's your name: My name is Leonardo\n",
      "What's your name: My name is Leonardo\n",
      "What's your name: None\n"
     ]
    },
    {
     "ename": "NameError",
     "evalue": "name 'function_inner_scope' is not defined",
     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mNameError\u001b[0m                                 Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-2-57ffd174d33a>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m     23\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34mf'What\\'s your name: {x}'\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     24\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 25\u001b[0;31m \u001b[0mfunction_inner_scope\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m   \u001b[0;31m# error - the funtion does not exist in this scope\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[0;31mNameError\u001b[0m: name 'function_inner_scope' is not defined"
     ]
    }
   ],
   "source": [
    "x = 'My_name is Renato'\n",
    "\n",
    "def function_main_scope():\n",
    "    x = 'My name is Pedro'\n",
    "    print(f'What\\'s your name: {x}')\n",
    "    \n",
    "    def function_inner_scope():\n",
    "        global x\n",
    "        print(f'What\\'s your name: {x}')\n",
    "        x = 'My name is Leonardo'\n",
    "        print(f'What\\'s your name: {x}')\n",
    "        #print(x)\n",
    "        return x\n",
    "    print(f'What\\'s your name: {x}')\n",
    "    x = function_inner_scope()\n",
    "    print(f'What\\'s your name: {x}')\n",
    "    \n",
    "    \n",
    "print(f'What\\'s your name: {x}')\n",
    "\n",
    "x = function_main_scope()\n",
    "\n",
    "print(f'What\\'s your name: {x}')\n",
    "\n",
    "function_inner_scope()   # NameError: name 'function_inner_scope' is not defined"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "***"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Functions receive parameters in the tuple \n",
    "    def <name of function>(parameters): \n",
    "### and return them with _return_ or _yield_  "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "1\n",
      "3\n"
     ]
    }
   ],
   "source": [
    "x = 1\n",
    "\n",
    "def increase(x):\n",
    "    print(x)\n",
    "    x += 1\n",
    "    \n",
    "    def increase_plus(x):\n",
    "        x += 1\n",
    "        return x\n",
    "    \n",
    "    x = increase_plus(x)\n",
    "    return x\n",
    "\n",
    "x = increase(x)\n",
    "print(x)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "***"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### [Global and local variables](https://www.programiz.com/python-programming/global-local-nonlocal-variables)  \n",
    "### Commands _global_ and _nonlocal_  "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "After local assignment: The original local spam\n",
      "After nonlocal assignment: this is neither local nor global spam\n",
      "After global assignment: this is neither local nor global spam\n",
      "Printing in global scope: this is the new global spam\n"
     ]
    }
   ],
   "source": [
    "def scope_test():\n",
    "    def do_local():\n",
    "        spam = \"this is the local spam\"\n",
    "        \n",
    "    def do_nonlocal():\n",
    "        nonlocal spam\n",
    "        spam = \"this is neither local nor global spam\"\n",
    "        \n",
    "    def do_global():\n",
    "        global spam\n",
    "        spam = \"this is the new global spam\"\n",
    "        \n",
    "    spam = \"The original local spam\"\n",
    "    \n",
    "    do_local()\n",
    "    print(\"After local assignment:\", spam)\n",
    "    do_nonlocal()\n",
    "    print(\"After nonlocal assignment:\", spam)\n",
    "    do_global()\n",
    "    print(\"After global assignment:\", spam)\n",
    "\n",
    "spam = \"The original global spam\"\n",
    "\n",
    "scope_test()\n",
    "\n",
    "print(\"Printing in global scope:\", spam)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Another example in a _for_ loop"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0\n",
      "4\n",
      "5\n",
      "6\n",
      "1\n",
      "4\n",
      "5\n",
      "6\n",
      "2\n",
      "4\n",
      "5\n",
      "6\n"
     ]
    }
   ],
   "source": [
    "for same_name in range(3):\n",
    "    print(same_name)\n",
    "    for same_name in range(4,7):\n",
    "        print(same_name)"
   ]
  }
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