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contain method

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rasbt 2014-06-15 23:23:19 -04:00
parent 844a1560a3
commit 163058f1f1
1 changed files with 261 additions and 2 deletions
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263
tutorials/key_differences_between_python_2_and_3.ipynb
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@ -1,7 +1,7 @@
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@ -872,11 +872,270 @@
"output_type": "pyerr", "output_type": "pyerr",
"traceback": [ "traceback": [
"\u001b[0;31m---------------------------------------------------------------------------\u001b[0m\n\u001b[0;31mNameError\u001b[0m Traceback (most recent call last)", "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m\n\u001b[0;31mNameError\u001b[0m Traceback (most recent call last)",
"\u001b[0;32m<ipython-input-8-5d8f9b79ea70>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mxrange\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[0m", "\u001b[0;32m<ipython-input-5-5d8f9b79ea70>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mxrange\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[0m",
"\u001b[0;31mNameError\u001b[0m: name 'xrange' is not defined" "\u001b[0;31mNameError\u001b[0m: name 'xrange' is not defined"
] ]
} }
], ],
"prompt_number": 5
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<a id='contains'></a>\n",
"<br>\n",
"<br>\n"
]
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"The `__contain__` method for `range` objects in Python 3"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Another thing worth mentioning is that `range` got a \"new\" `__contains__` method in Python 3.x (thanks to [yegle](), who pointed this out). The `__contains__` method can speedup \"look-ups\" in Python 3.x `range` significantly for integer and bolean types.\n"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = 10000000"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 4
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def val_in_range(x, val):\n",
" if val in range(x):\n",
" return True\n",
" else:\n",
" return False"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 10
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def val_in_xrange(x, val):\n",
" if val in range(x):\n",
" return True\n",
" else:\n",
" return False"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 5
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print('Python', python_version())\n",
"assert(val_in_range(x, x/2) == True)\n",
"assert(val_in_range(x, x//2) == True)\n",
"%timeit val_in_range(x, x/2)\n",
"%timeit val_in_range(x, x//2)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Python 3.3.5\n",
"1 loops, best of 3: 751 ms per loop"
]
},
{
"output_type": "stream",
"stream": "stdout",
"text": [
"\n",
"1000000 loops, best of 3: 1.21 \u00b5s per loop"
]
},
{
"output_type": "stream",
"stream": "stdout",
"text": [
"\n"
]
}
],
"prompt_number": 11
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Based on the `timeit` results above, you see that the execution for the \"look up\" was about 60,000 faster when it was of an integer type rather than a float. However, since Python 2.x's `range` or `xrange` doesn't have a `__contains__` method, the \"look-up speed\" wouldn't be that much different for integers or floats:"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<br>"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print 'Python', python_version()\n",
"assert(val_in_xrange(x, x/2.0) == True)\n",
"assert(val_in_xrange(x, x/2) == True)\n",
"%timeit val_in_xrange(x, x/2.0)\n",
"%timeit val_in_xrange(x, x/2)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Python 2.7.7\n",
"1 loops, best of 3: 661 ms per loop"
]
},
{
"output_type": "stream",
"stream": "stdout",
"text": [
"\n",
"1 loops, best of 3: 564 ms per loop"
]
},
{
"output_type": "stream",
"stream": "stdout",
"text": [
"\n"
]
}
],
"prompt_number": 6
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<br>"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Below the \"proofs\" that the `__contain__` method wasn't added to Python 2.x yet:"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print('Python', python_version())\n",
"range.__contains__"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Python 3.4.1\n"
]
},
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 2,
"text": [
"<slot wrapper '__contains__' of 'range' objects>"
]
}
],
"prompt_number": 2
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print 'Python', python_version()\n",
"range.__contains__"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Python 2.7.7\n"
]
},
{
"ename": "AttributeError",
"evalue": "'builtin_function_or_method' object has no attribute '__contains__'",
"output_type": "pyerr",
"traceback": [
"\u001b[0;31m---------------------------------------------------------------------------\u001b[0m\n\u001b[0;31mAttributeError\u001b[0m Traceback (most recent call last)",
"\u001b[0;32m<ipython-input-7-05327350dafb>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[1;32m 1\u001b[0m \u001b[0;32mprint\u001b[0m \u001b[0;34m'Python'\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mpython_version\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 2\u001b[0;31m \u001b[0mrange\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m__contains__\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
"\u001b[0;31mAttributeError\u001b[0m: 'builtin_function_or_method' object has no attribute '__contains__'"
]
}
],
"prompt_number": 7
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print 'Python', python_version()\n",
"xrange.__contains__"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Python 2.7.7\n"
]
},
{
"ename": "AttributeError",
"evalue": "type object 'xrange' has no attribute '__contains__'",
"output_type": "pyerr",
"traceback": [
"\u001b[0;31m---------------------------------------------------------------------------\u001b[0m\n\u001b[0;31mAttributeError\u001b[0m Traceback (most recent call last)",
"\u001b[0;32m<ipython-input-8-7d1a71bfee8e>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[1;32m 1\u001b[0m \u001b[0;32mprint\u001b[0m \u001b[0;34m'Python'\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mpython_version\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 2\u001b[0;31m \u001b[0mxrange\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m__contains__\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
"\u001b[0;31mAttributeError\u001b[0m: type object 'xrange' has no attribute '__contains__'"
]
}
],
"prompt_number": 8 "prompt_number": 8
}, },
{ {