From f8ebfc8dd032743f7862eb934a90734d9f488465 Mon Sep 17 00:00:00 2001
From: rasbt <se.raschka@me.com>
Date: Tue, 15 Apr 2014 18:33:51 -0400
Subject: [PATCH] mutable objects as default arguments

---
 ...t_so_obvious_python_stuff-checkpoint.ipynb | 87 ++++++++++++-------
 not_so_obvious_python_stuff.ipynb             | 12 +--
 2 files changed, 64 insertions(+), 35 deletions(-)

diff --git a/.ipynb_checkpoints/not_so_obvious_python_stuff-checkpoint.ipynb b/.ipynb_checkpoints/not_so_obvious_python_stuff-checkpoint.ipynb
index 1e3b56c..f7ca828 100644
--- a/.ipynb_checkpoints/not_so_obvious_python_stuff-checkpoint.ipynb
+++ b/.ipynb_checkpoints/not_so_obvious_python_stuff-checkpoint.ipynb
@@ -1,7 +1,7 @@
 {
  "metadata": {
   "name": "",
-  "signature": "sha256:5c0e4a56352cc8a60aa6e2ced2611bc186078af3c849647256f0c4a810004ee9"
+  "signature": "sha256:b6e7356842906c447ef3c7520aac098e7fe4f888e46fdd5ae06905f1ebe68e27"
  },
  "nbformat": 3,
  "nbformat_minor": 0,
@@ -48,7 +48,8 @@
       "- [`bool` is a subclass of `int`](#bool_int)\n",
       "- [About lambda and closures-in-a-loop pitfall](#lambda_closure)\n",
       "- [Python's LEGB scope resolution and the keywords `global` and `nonlocal`](#python_legb)\n",
-      "- [When immutable Tuples aren't so immutable](#immutable_tuple)"
+      "- [When immutable Tuples aren't so immutable](#immutable_tuple)\n",
+      "- [List comprehensions are fast, but generators are faster!?](#list_generator)"
      ]
     },
     {
@@ -966,7 +967,15 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "## List comprehensions are fast, but generators are faster!\n"
+      "<br>\n",
+      "<br>\n",
+      "<a name='list_generator'></a>\n",
+      "\n",
+      "## List comprehensions are fast, but generators are faster!?\n",
+      "\n",
+      "Not, really (or significantly, see the benchmarks below). So what's the reason to prefer one over the other?\n",
+      "- use lists if you want to use list methods  \n",
+      "- use generators when you are dealing with huge collections to avoid memory issues"
      ]
     },
     {
@@ -975,30 +984,30 @@
      "input": [
       "import timeit\n",
       "\n",
-      "def plainlist():\n",
+      "def plainlist(n=100000):\n",
       "    my_list = []\n",
-      "    for i in range(1,1000000):\n",
+      "    for i in range(n):\n",
       "        if i % 5 == 0:\n",
       "            my_list.append(i)\n",
       "    return my_list\n",
       "\n",
-      "def listcompr():\n",
-      "    my_list = [i for i in range(1,1000000) if i % 5 == 0]\n",
+      "def listcompr(n=100000):\n",
+      "    my_list = [i for i in range(n) if i % 5 == 0]\n",
       "    return my_list\n",
       "\n",
-      "def generator():\n",
-      "    my_gen = (i for i in range(1,1000000) if i % 5 == 0)\n",
+      "def generator(n=100000):\n",
+      "    my_gen = (i for i in range(n) if i % 5 == 0)\n",
       "    return my_gen\n",
       "\n",
-      "def generator_yield():\n",
-      "    for i in range(1,1000000):\n",
+      "def generator_yield(n=100000):\n",
+      "    for i in range(n):\n",
       "        if i % 5 == 0:\n",
       "            yield i"
      ],
      "language": "python",
      "metadata": {},
      "outputs": [],
-     "prompt_number": 60
+     "prompt_number": 75
     },
     {
      "cell_type": "markdown",
@@ -1027,10 +1036,13 @@
       "    for i in listcompr:\n",
       "        print(i)\n",
       "\n",
-      "print('plain_list', end = '')\n",
+      "print('plain_list:     ', end = '')\n",
       "%timeit test_plainlist\n",
+      "print('\\nlistcompr:     ', end = '')\n",
       "%timeit test_listcompr\n",
+      "print('\\ngenerator:     ', end = '')\n",
       "%timeit test_generator\n",
+      "print('\\ngenerator_yield:     ', end = '')\n",
       "%timeit test_generator_yield"
      ],
      "language": "python",
@@ -1040,28 +1052,45 @@
        "output_type": "stream",
        "stream": "stdout",
        "text": [
-        "plain_list"
+        "plain_list:     10000000 loops, best of 3: 26.2 ns per loop"
        ]
       },
       {
-       "ename": "NameError",
-       "evalue": "global name 'test_plainlist' is not defined",
-       "output_type": "pyerr",
-       "traceback": [
-        "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m\n\u001b[0;31mNameError\u001b[0m                                 Traceback (most recent call last)",
-        "\u001b[0;32m<ipython-input-62-a2bedd84850f>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[1;32m     16\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     17\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m'plain_list'\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mend\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;34m''\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 18\u001b[0;31m \u001b[0mget_ipython\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mmagic\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m'timeit test_plainlist'\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     19\u001b[0m \u001b[0mget_ipython\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mmagic\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m'timeit test_listcompr'\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     20\u001b[0m \u001b[0mget_ipython\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mmagic\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m'timeit test_generator'\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
-        "\u001b[0;32m/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/site-packages/IPython/core/interactiveshell.py\u001b[0m in \u001b[0;36mmagic\u001b[0;34m(self, arg_s)\u001b[0m\n\u001b[1;32m   2203\u001b[0m         \u001b[0mmagic_name\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0m_\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mmagic_arg_s\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0marg_s\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mpartition\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m' '\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m   2204\u001b[0m         \u001b[0mmagic_name\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mmagic_name\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mlstrip\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mprefilter\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mESC_MAGIC\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m-> 2205\u001b[0;31m         \u001b[0;32mreturn\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mrun_line_magic\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mmagic_name\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mmagic_arg_s\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m   2206\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m   2207\u001b[0m     \u001b[0;31m#-------------------------------------------------------------------------\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
-        "\u001b[0;32m/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/site-packages/IPython/core/interactiveshell.py\u001b[0m in \u001b[0;36mrun_line_magic\u001b[0;34m(self, magic_name, line)\u001b[0m\n\u001b[1;32m   2124\u001b[0m                 \u001b[0mkwargs\u001b[0m\u001b[0;34m[\u001b[0m\u001b[0;34m'local_ns'\u001b[0m\u001b[0;34m]\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0msys\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m_getframe\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mstack_depth\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mf_locals\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m   2125\u001b[0m             \u001b[0;32mwith\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mbuiltin_trap\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m-> 2126\u001b[0;31m                 \u001b[0mresult\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mfn\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m*\u001b[0m\u001b[0margs\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;34m**\u001b[0m\u001b[0mkwargs\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m   2127\u001b[0m             \u001b[0;32mreturn\u001b[0m \u001b[0mresult\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m   2128\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n",
-        "\u001b[0;32m/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/site-packages/IPython/core/magics/execution.py\u001b[0m in \u001b[0;36mtimeit\u001b[0;34m(self, line, cell)\u001b[0m\n",
-        "\u001b[0;32m/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/site-packages/IPython/core/magic.py\u001b[0m in \u001b[0;36m<lambda>\u001b[0;34m(f, *a, **k)\u001b[0m\n\u001b[1;32m    191\u001b[0m     \u001b[0;31m# but it's overkill for just that one bit of state.\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    192\u001b[0m     \u001b[0;32mdef\u001b[0m \u001b[0mmagic_deco\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0marg\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m--> 193\u001b[0;31m         \u001b[0mcall\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;32mlambda\u001b[0m \u001b[0mf\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m*\u001b[0m\u001b[0ma\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m**\u001b[0m\u001b[0mk\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mf\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m*\u001b[0m\u001b[0ma\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m**\u001b[0m\u001b[0mk\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m    194\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    195\u001b[0m         \u001b[0;32mif\u001b[0m \u001b[0mcallable\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0marg\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
-        "\u001b[0;32m/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/site-packages/IPython/core/magics/execution.py\u001b[0m in \u001b[0;36mtimeit\u001b[0;34m(self, line, cell)\u001b[0m\n\u001b[1;32m   1011\u001b[0m             \u001b[0mnumber\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;36m1\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m   1012\u001b[0m             \u001b[0;32mfor\u001b[0m \u001b[0m_\u001b[0m \u001b[0;32min\u001b[0m \u001b[0mrange\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;36m1\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;36m10\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m-> 1013\u001b[0;31m                 \u001b[0;32mif\u001b[0m \u001b[0mtimer\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mtimeit\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mnumber\u001b[0m\u001b[0;34m)\u001b[0m \u001b[0;34m>=\u001b[0m \u001b[0;36m0.2\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m   1014\u001b[0m                     \u001b[0;32mbreak\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m   1015\u001b[0m                 \u001b[0mnumber\u001b[0m \u001b[0;34m*=\u001b[0m \u001b[0;36m10\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
-        "\u001b[0;32m/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/timeit.py\u001b[0m in \u001b[0;36mtimeit\u001b[0;34m(self, number)\u001b[0m\n\u001b[1;32m    188\u001b[0m         \u001b[0mgc\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mdisable\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    189\u001b[0m         \u001b[0;32mtry\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m--> 190\u001b[0;31m             \u001b[0mtiming\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0minner\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mit\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mtimer\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m    191\u001b[0m         \u001b[0;32mfinally\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    192\u001b[0m             \u001b[0;32mif\u001b[0m \u001b[0mgcold\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
-        "\u001b[0;32m<magic-timeit>\u001b[0m in \u001b[0;36minner\u001b[0;34m(_it, _timer)\u001b[0m\n",
-        "\u001b[0;31mNameError\u001b[0m: global name 'test_plainlist' is not defined"
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "\n",
+        "\n",
+        "listcompr:     10000000 loops, best of 3: 26.1 ns per loop"
+       ]
+      },
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "\n",
+        "\n",
+        "generator:     10000000 loops, best of 3: 25.9 ns per loop"
+       ]
+      },
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "\n",
+        "\n",
+        "generator_yield:     10000000 loops, best of 3: 26 ns per loop"
+       ]
+      },
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "\n"
        ]
       }
      ],
-     "prompt_number": 62
+     "prompt_number": 76
     },
     {
      "cell_type": "code",
diff --git a/not_so_obvious_python_stuff.ipynb b/not_so_obvious_python_stuff.ipynb
index 66a70bc..f7ca828 100644
--- a/not_so_obvious_python_stuff.ipynb
+++ b/not_so_obvious_python_stuff.ipynb
@@ -1,7 +1,7 @@
 {
  "metadata": {
   "name": "",
-  "signature": "sha256:a2c062243bccabbfe46e6f62bbc9d6dd5b10fe44d091727781108ba5b87b9e28"
+  "signature": "sha256:b6e7356842906c447ef3c7520aac098e7fe4f888e46fdd5ae06905f1ebe68e27"
  },
  "nbformat": 3,
  "nbformat_minor": 0,
@@ -48,7 +48,8 @@
       "- [`bool` is a subclass of `int`](#bool_int)\n",
       "- [About lambda and closures-in-a-loop pitfall](#lambda_closure)\n",
       "- [Python's LEGB scope resolution and the keywords `global` and `nonlocal`](#python_legb)\n",
-      "- [When immutable Tuples aren't so immutable](#immutable_tuple)"
+      "- [When immutable Tuples aren't so immutable](#immutable_tuple)\n",
+      "- [List comprehensions are fast, but generators are faster!?](#list_generator)"
      ]
     },
     {
@@ -967,9 +968,10 @@
      "metadata": {},
      "source": [
       "<br>\n",
+      "<br>\n",
+      "<a name='list_generator'></a>\n",
       "\n",
-      "\n",
-      "## List comprehensions are fast, but generators are faster!\n",
+      "## List comprehensions are fast, but generators are faster!?\n",
       "\n",
       "Not, really (or significantly, see the benchmarks below). So what's the reason to prefer one over the other?\n",
       "- use lists if you want to use list methods  \n",
@@ -1018,8 +1020,6 @@
      "cell_type": "code",
      "collapsed": false,
      "input": [
-      "\n",
-      "\n",
       "def test_plainlist(plain_list):\n",
       "    for i in plain_list:\n",
       "        print(i)\n",