mutable objects as default arguments

rasbt · rasbt · commit a305b990c488 · 2014-04-15T16:37:08.000-04:00
diff --git 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": "sha256:0c860c383edcd7622b0c660eb989513e90496c7350916bae1ddb6c10f29fab2c"
+  "signature": "sha256:611615765638a390c8e9093179758c4a23524ddcc2379aeff80e51c22031aa18"
  },
  "nbformat": 3,
  "nbformat_minor": 0,
@@ -225,6 +225,64 @@
      ],
      "prompt_number": 5
     },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Another popular example to illustrate the reuse of objects for small integers is:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "print(256 is 257 - 1)\n",
+      "print(257 is 258 - 1)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "True\n",
+        "False\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "And to illustrate the test for equality (`==`) vs. identity (`is`):"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "a = 'hello world!'\n",
+      "b = 'hello world!'\n",
+      "print('a is b', a is b)\n",
+      "print('a == b', a == b)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "a is b False\n",
+        "a == b True\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
     {
      "cell_type": "markdown",
      "metadata": {},
diff --git a/not_so_obvious_python_stuff.ipynb b/not_so_obvious_python_stuff.ipynb
@@ -1,7 +1,7 @@
 {
  "metadata": {
   "name": "",
-  "signature": "sha256:0c860c383edcd7622b0c660eb989513e90496c7350916bae1ddb6c10f29fab2c"
+  "signature": "sha256:611615765638a390c8e9093179758c4a23524ddcc2379aeff80e51c22031aa18"
  },
  "nbformat": 3,
  "nbformat_minor": 0,
@@ -225,6 +225,64 @@
      ],
      "prompt_number": 5
     },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Another popular example to illustrate the reuse of objects for small integers is:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "print(256 is 257 - 1)\n",
+      "print(257 is 258 - 1)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "True\n",
+        "False\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "And to illustrate the test for equality (`==`) vs. identity (`is`):"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "a = 'hello world!'\n",
+      "b = 'hello world!'\n",
+      "print('a is b', a is b)\n",
+      "print('a == b', a == b)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "a is b False\n",
+        "a == b True\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
     {
      "cell_type": "markdown",
      "metadata": {},
