tutorials/Don't use mutable objects as default arguments.ipynb

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    "<h1>Table of Contents<span class=\"tocSkip\"></span></h1>\n",
    "<div class=\"toc\"><ul class=\"toc-item\"><li><span><a href=\"#Introduction\" data-toc-modified-id=\"Introduction-1\"><span class=\"toc-item-num\">1&nbsp;&nbsp;</span>Introduction</a></span></li><li><span><a href=\"#Don't-use-mutable-objects-as-default-arguments-for-functions!\" data-toc-modified-id=\"Don't-use-mutable-objects-as-default-arguments-for-functions!-2\"><span class=\"toc-item-num\">2&nbsp;&nbsp;</span>Don't use mutable objects as default arguments for functions!</a></span></li><li><span><a href=\"#References\" data-toc-modified-id=\"References-3\"><span class=\"toc-item-num\">3&nbsp;&nbsp;</span>References</a></span></li></ul></div>"
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   "source": [
    "# Introduction\n",
    "<hr style = \"border:2px solid black\" ></hr>"
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    "<div class=\"alert alert-warning\">\n",
    "<font color=black>\n",
    "\n",
    "**What?** Don't use mutable objects as default arguments\n",
    "\n",
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    "# Don't use mutable objects as default arguments for functions!\n",
    "<hr style = \"border:2px solid black\" ></hr>"
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    "<div class=\"alert alert-info\">\n",
    "<font color=black>\n",
    "\n",
    "- Don't use mutable objects (e.g., dictionaries, lists, sets, etc.) as default arguments for functions!\n",
    "- You might expect that a new list is created every time when we call the function without providing an argument for the default parameter, but this is not the case: **Python will create the mutable object (default parameter) the first time the function is defined - not when it is called**.\n",
    "\n",
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    "def append_to_list(value, def_list=[]):\n",
    "    def_list.append(value)\n",
    "    return def_list\n",
    "\n",
    "my_list = append_to_list(1)\n",
    "print(my_list)\n",
    "\n",
    "my_other_list = append_to_list(2)\n",
    "print(my_other_list)"
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    "<div class=\"alert alert-info\">\n",
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    "    \n",
    "- Another good example showing that demonstrates that default arguments are created when the function is created (**and not when it is called!**)\n",
    "\n",
    "</font>\n",
    "</div>"
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      "1528560045.3962939\n",
      "1528560045.3962939\n"
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   "source": [
    "import time\n",
    "def report_arg(my_default=time.time()):\n",
    "    print(my_default)\n",
    "\n",
    "report_arg()\n",
    "\n",
    "time.sleep(5)\n",
    "\n",
    "report_arg()"
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   "source": [
    "# References\n",
    "<hr style = \"border:2px solid black\" ></hr>"
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    "<div class=\"alert alert-warning\">\n",
    "<font color=black>\n",
    "\n",
    "- https://nbviewer.org/github/rasbt/python_reference/blob/master/tutorials/not_so_obvious_python_stuff.ipynb?create=1\n",
    "- http://docs.python-guide.org/en/latest/writing/gotchas/\n",
    "    \n",
    "</font>\n",
    "</div>"
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