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anandology/Advanced Python Workshop - Day 1.ipynb

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Advanced Python Workshop August 2-4, 2013 http://advancedpython.hasgeek.com/
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Advanced Python Workshop - Day 1.ipynb
{
"metadata": {
"name": "Advanced Python Workshop - Day 1"
},
"nbformat": 3,
"nbformat_minor": 0,
"worksheets": [
{
"cells": [
{
"cell_type": "markdown",
"metadata": {},
"source": [
"# Advanced Python Workshop - Day 1\n",
"[[Day 1]](http://nbviewer.ipython.org/6137954/Advanced%20Python%20Workshop%20-%20Day%201.ipynb) - \n",
"[[Day 2]](http://nbviewer.ipython.org/6137954/Advanced%20Python%20Workshop%20-%20Day%202.ipynb) - \n",
"[[Day 3]](http://nbviewer.ipython.org/6137954/Advanced%20Python%20Workshop%20-%20Day%203.ipynb)\n",
"\n",
"August 2-4, 2013 <br/>\n",
"by [Anand Chitipothu](http://anandology.com/) <br/>\n",
"<http://advancedpython.hasgeek.com/>"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = 1\n",
"y = x\n",
"x = 2\n",
"print x, y"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"2 1\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = [1, 2]\n",
"y = [x, 5]\n",
"x.append(3)\n",
"print y"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"[[1, 2, 3], 5]\n"
]
}
],
"prompt_number": 2
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = [1, 2]\n",
"y = [x, 5]\n",
"x = [1, 2, 3]\n",
"print y"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"[[1, 2], 5]\n"
]
}
],
"prompt_number": 3
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def append(x, a):\n",
" x.append(a)\n",
" \n",
"p = [1, 2]\n",
"append(p, 3)\n",
"print p"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"[1, 2, 3]\n"
]
}
],
"prompt_number": 4
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Default Arguments to functions**"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def inc(x, amount=1):\n",
" return x + amount\n",
"\n",
"x = 4\n",
"print inc(x)\n",
"print inc(x, 3)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"5\n",
"7\n"
]
}
],
"prompt_number": 5
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def inc2(x, amount=1):\n",
" x = x + amount\n",
" return x\n",
"\n",
"x = 4\n",
"print inc2(x)\n",
"print x\n",
"print inc2(x, 3)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"5\n",
"4\n",
"7\n"
]
}
],
"prompt_number": 6
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Python is strongly typed."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\"1\" + 2"
],
"language": "python",
"metadata": {},
"outputs": [
{
"ename": "TypeError",
"evalue": "cannot concatenate 'str' and 'int' objects",
"output_type": "pyerr",
"traceback": [
"\u001b[0;31m---------------------------------------------------------------------------\u001b[0m\n\u001b[0;31mTypeError\u001b[0m Traceback (most recent call last)",
"\u001b[0;32m<ipython-input-7-e83767cb1e37>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0;34m\"1\"\u001b[0m \u001b[0;34m+\u001b[0m \u001b[0;36m2\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
"\u001b[0;31mTypeError\u001b[0m: cannot concatenate 'str' and 'int' objects"
]
}
],
"prompt_number": 7
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Lets go back to default args."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def f(x):\n",
" print \"f is called with arg\", x\n",
" return x\n",
"\n",
"print \"before defining inc\"\n",
"def inc3(x, amount=f(1)):\n",
" return x + amount\n",
"print \"after defining inc\"\n",
"print inc3(5)\n",
"print inc3(10)\n",
"print \"end\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"before defining inc\n",
"f is called with arg 1\n",
"after defining inc\n",
"6\n",
"11\n",
"end\n"
]
}
],
"prompt_number": 8
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"default values are evaluated when the function is defined."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def f(x):\n",
" print \"f is called with arg\", x\n",
" return x\n",
"\n",
"y = 1\n",
"print \"before defining inc\"\n",
"def inc3(x, amount=f(y)):\n",
" return x + amount\n",
"print \"after defining inc\"\n",
"print inc3(5)\n",
"y = 2\n",
"print inc3(10)\n",
"print \"end\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"before defining inc\n",
"f is called with arg 1\n",
"after defining inc\n",
"6\n",
"11\n",
"end\n"
]
}
],
"prompt_number": 9
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"inc3"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 10,
"text": [
"<function __main__.inc3>"
]
}
],
"prompt_number": 10
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"dir(inc3)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 11,
"text": [
"['__call__',\n",
" '__class__',\n",
" '__closure__',\n",
" '__code__',\n",
" '__defaults__',\n",
" '__delattr__',\n",
" '__dict__',\n",
" '__doc__',\n",
" '__format__',\n",
" '__get__',\n",
" '__getattribute__',\n",
" '__globals__',\n",
" '__hash__',\n",
" '__init__',\n",
" '__module__',\n",
" '__name__',\n",
" '__new__',\n",
" '__reduce__',\n",
" '__reduce_ex__',\n",
" '__repr__',\n",
" '__setattr__',\n",
" '__sizeof__',\n",
" '__str__',\n",
" '__subclasshook__',\n",
" 'func_closure',\n",
" 'func_code',\n",
" 'func_defaults',\n",
" 'func_dict',\n",
" 'func_doc',\n",
" 'func_globals',\n",
" 'func_name']"
]
}
],
"prompt_number": 11
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"inc3.func_defaults"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 12,
"text": [
"(1,)"
]
}
],
"prompt_number": 12
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"inc3.func_defaults = (2,)"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 13
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"inc3(5)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 14,
"text": [
"7"
]
}
],
"prompt_number": 14
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def f(a, x=[]):\n",
" x.append(a)\n",
" return x\n",
"\n",
"print f(0, [1, 2])\n",
"print f(1)\n",
"print f(2)\n",
"print f(0, [1, 2])"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"[1, 2, 0]\n",
"[1]\n",
"[1, 2]\n",
"[1, 2, 0]\n"
]
}
],
"prompt_number": 15
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"How to fix this?"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def f(a, x=None):\n",
" if x is None:\n",
" x = []\n",
" x.append(a)\n",
" return x\n",
"\n",
"print f(0, [1, 2])\n",
"print f(1)\n",
"print f(2)\n",
"print f(0, [1, 2])"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"[1, 2, 0]\n",
"[1]\n",
"[2]\n",
"[1, 2, 0]\n"
]
}
],
"prompt_number": 16
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Iterators and Generators"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"for a in [1,2,3,4]:\n",
" print a"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"1\n",
"2\n",
"3\n",
"4\n"
]
}
],
"prompt_number": 20
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"for a in (1, 2, 3, 4):\n",
" print a"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"1\n",
"2\n",
"3\n",
"4\n"
]
}
],
"prompt_number": 21
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"for k in {\"x\": 1, \"y\": 2, \"z\": 3}:\n",
" print k"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"y\n",
"x\n",
"z\n"
]
}
],
"prompt_number": 22
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"for c in \"hello\":\n",
" print c"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"h\n",
"e\n",
"l\n",
"l\n",
"o\n"
]
}
],
"prompt_number": 24
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\",\".join([\"a\", \"b\", \"c\"])"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 25,
"text": [
"'a,b,c'"
]
}
],
"prompt_number": 25
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\",\".join((\"a\", \"b\", \"c\"))"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 26,
"text": [
"'a,b,c'"
]
}
],
"prompt_number": 26
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\",\".join({\"x\": 1, \"y\": 2, \"z\": 3})"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 27,
"text": [
"'y,x,z'"
]
}
],
"prompt_number": 27
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Will the order of keys in dict be same always?\n",
"Yes, if you use the same dict."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"d = {\"x\": 1, \"y\": 2, \"z\": 3}"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 28
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"d.keys()"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 29,
"text": [
"['y', 'x', 'z']"
]
}
],
"prompt_number": 29
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"max([1, 2, 3, 4])"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 33,
"text": [
"4"
]
}
],
"prompt_number": 33
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"max({\"x\": 1, \"y\": 2, \"z\": 3})"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 34,
"text": [
"'z'"
]
}
],
"prompt_number": 34
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = iter([1, 2, 3])"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 44
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"next(x)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 45,
"text": [
"1"
]
}
],
"prompt_number": 45
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"next(x)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 46,
"text": [
"2"
]
}
],
"prompt_number": 46
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"next(x)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 47,
"text": [
"3"
]
}
],
"prompt_number": 47
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"next(x)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"ename": "StopIteration",
"evalue": "",
"output_type": "pyerr",
"traceback": [
"\u001b[0;31m---------------------------------------------------------------------------\u001b[0m\n\u001b[0;31mStopIteration\u001b[0m Traceback (most recent call last)",
"\u001b[0;32m<ipython-input-40-5e4e57af3a97>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mnext\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mx\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
"\u001b[0;31mStopIteration\u001b[0m: "
]
}
],
"prompt_number": 40
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Before Python 2.6, the next element is got by calling `x.next()`. In Python 2.7, a builtin `next` is added and that is the only way in Python 3."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"y = iter([1, 2, 3])"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 49
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"y.next()"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 50,
"text": [
"1"
]
}
],
"prompt_number": 50
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"y.next()"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 52,
"text": [
"2"
]
}
],
"prompt_number": 52
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"y.next()"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 53,
"text": [
"3"
]
}
],
"prompt_number": 53
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"y.next()"
],
"language": "python",
"metadata": {},
"outputs": [
{
"ename": "StopIteration",
"evalue": "",
"output_type": "pyerr",
"traceback": [
"\u001b[0;31m---------------------------------------------------------------------------\u001b[0m\n\u001b[0;31mStopIteration\u001b[0m Traceback (most recent call last)",
"\u001b[0;32m<ipython-input-54-75a92ee8313a>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0my\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mnext\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
"\u001b[0;31mStopIteration\u001b[0m: "
]
}
],
"prompt_number": 54
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Lets implememt something like `xrange`."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"for i in xrange(4):\n",
" print i,"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"0 1 2 3\n"
]
}
],
"prompt_number": 55
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"xrange(4)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 56,
"text": [
"xrange(4)"
]
}
],
"prompt_number": 56
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"class yrange:\n",
" def __init__(self, n):\n",
" self.n = n\n",
" self.i = 0\n",
" \n",
" def __iter__(self):\n",
" return self\n",
" \n",
" def next(self):\n",
" print \"next called\", self.i\n",
" i = self.i\n",
" if i < self.n:\n",
" self.i += 1\n",
" return i\n",
" raise StopIteration()"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 66
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"yrange(4)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 67,
"text": [
"<__main__.yrange instance at 0x101f9f6c8>"
]
}
],
"prompt_number": 67
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"for i in yrange(4): print i,"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"0 1 2 3\n"
]
}
],
"prompt_number": 60
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"y = yrange(4)\n",
"it = iter(y)\n",
"print next(it)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"next called 0\n",
"0\n"
]
}
],
"prompt_number": 68
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print next(it)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"next called 1\n",
"1\n"
]
}
],
"prompt_number": 69
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print next(it)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"next called 2\n",
"2\n"
]
}
],
"prompt_number": 70
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print next(it)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"next called 3\n",
"3\n"
]
}
],
"prompt_number": 71
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print next(it)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"ename": "StopIteration",
"evalue": "",
"output_type": "pyerr",
"traceback": [
"\u001b[0;31m---------------------------------------------------------------------------\u001b[0m\n\u001b[0;31mStopIteration\u001b[0m Traceback (most recent call last)",
"\u001b[0;32m<ipython-input-72-b9b0e582689c>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0;32mprint\u001b[0m \u001b[0mnext\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mit\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
"\u001b[0;31mStopIteration\u001b[0m: "
]
},
{
"output_type": "stream",
"stream": "stdout",
"text": [
"next called 4\n"
]
}
],
"prompt_number": 72
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"What happens when we overwrite a builtin function?"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def f(): return 1\n",
"def f(): return 2\n",
"print f()"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"2\n"
]
}
],
"prompt_number": 73
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"The last defination overwrites the previous ones."
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Generators**"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def numbers():\n",
" print \"begin\"\n",
" yield 1\n",
" print \"after 1\"\n",
" yield 2\n",
" print \"after 2\"\n",
" yield 3\n",
" print \"end\"\n",
" "
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 76
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"for i in numbers(): print i"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"begin\n",
"1\n",
"after 1\n",
"2\n",
"after 2\n",
"3\n",
"end\n"
]
}
],
"prompt_number": 77
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = numbers()"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 78
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 79,
"text": [
"<generator object numbers at 0x101faa0a0>"
]
}
],
"prompt_number": 79
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"next(x)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"begin\n"
]
},
{
"output_type": "pyout",
"prompt_number": 80,
"text": [
"1"
]
}
],
"prompt_number": 80
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"next(x)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"after 1\n"
]
},
{
"output_type": "pyout",
"prompt_number": 81,
"text": [
"2"
]
}
],
"prompt_number": 81
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"next(x)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"after 2\n"
]
},
{
"output_type": "pyout",
"prompt_number": 82,
"text": [
"3"
]
}
],
"prompt_number": 82
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"next(x)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"ename": "StopIteration",
"evalue": "",
"output_type": "pyerr",
"traceback": [
"\u001b[0;31m---------------------------------------------------------------------------\u001b[0m\n\u001b[0;31mStopIteration\u001b[0m Traceback (most recent call last)",
"\u001b[0;32m<ipython-input-83-5e4e57af3a97>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mnext\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mx\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
"\u001b[0;31mStopIteration\u001b[0m: "
]
},
{
"output_type": "stream",
"stream": "stdout",
"text": [
"end\n"
]
}
],
"prompt_number": 83
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem:** Implement `yrange` as a generator function."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"%%file yrange.py\n",
"def yrange(n):\n",
" i = 0\n",
" while i < n:\n",
" yield i\n",
" i += 1\n",
" \n",
"for i in yrange(10):\n",
" print i,"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Overwriting yrange.py\n"
]
}
],
"prompt_number": 104
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"!python yrange.py"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"0 1 2 3 4 5 6 7 8 9\r\n"
]
}
],
"prompt_number": 105
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def squares(numbers):\n",
" for n in numbers:\n",
" yield n*n"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 85
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"sum(squares(yrange(1000000)))"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 86,
"text": [
"333332833333500000"
]
}
],
"prompt_number": 86
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"The `file` object in Python is iterable."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"%%file numbers.txt\n",
"one\n",
"two\n",
"three\n",
"four\n",
"five"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Overwriting numbers.txt\n"
]
}
],
"prompt_number": 88
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"f = open(\"numbers.txt\")"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 89
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"f"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 90,
"text": [
"<open file 'numbers.txt', mode 'r' at 0x101ebbb70>"
]
}
],
"prompt_number": 90
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"for line in f: print line"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"one\n",
"\n",
"two\n",
"\n",
"three\n",
"\n",
"four\n",
"\n",
"five\n"
]
}
],
"prompt_number": 91
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"%%file grep.py\n",
"import sys\n",
"def grep(pattern, lines):\n",
" for line in lines:\n",
" #print \"grep\", repr(line)\n",
" if pattern in line:\n",
" yield line\n",
" \n",
"def uppercase(seq):\n",
" for x in seq:\n",
" #print \"uppercase\", repr(x)\n",
" yield x.upper()\n",
" \n",
"def print_lines(lines):\n",
" for line in lines:\n",
" #print \"print_lines\", repr(line)\n",
" print line.strip(\"\\n\")\n",
" \n",
"def main():\n",
" pattern = sys.argv[1]\n",
" filename = sys.argv[2]\n",
" f = open(filename)\n",
" lines = grep(pattern, f)\n",
" print_lines(lines)\n",
" \n",
"if __name__ == \"__main__\":\n",
" main()"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Writing grep.py\n"
]
}
],
"prompt_number": 18
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"!python grep.py def grep.py"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"def grep(pattern, lines):\r\n",
"def uppercase(seq):\r\n",
"def print_lines(lines):\r\n",
"def main():\r\n"
]
}
],
"prompt_number": 120
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"%%file num.txt\n",
"1\n",
"2\n",
"3\n",
"4\n",
"5\n",
"6\n",
"7\n",
"8\n",
"9\n",
"10"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Writing num.txt\n"
]
}
],
"prompt_number": 121
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def toint(seq):\n",
" for x in seq:\n",
" yield int(x)\n",
"\n",
"sum(toint(open(\"num.txt\")))"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 122,
"text": [
"55"
]
}
],
"prompt_number": 122
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Quick Intro to command line aguments**"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Because we need them everywhere."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"%%file echo.py\n",
"import sys\n",
"print sys.argv[1]"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Writing echo.py\n"
]
}
],
"prompt_number": 22
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"!python echo.py hello "
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"hello\r\n"
]
}
],
"prompt_number": 129
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"%%file square.py\n",
"import sys\n",
"\n",
"def square(x):\n",
" return x*x\n",
"\n",
"# Run this code only if executed as a script\n",
"# This won't be executed when this file imported\n",
"# as a module.\n",
"if __name__ == \"__main__\":\n",
" n = int(sys.argv[1])\n",
" print square(n)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Overwriting square.py\n"
]
}
],
"prompt_number": 21
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"!python square.py 5"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"25\r\n"
]
}
],
"prompt_number": 5
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Write a program add.py that takes 2 arguments and prints their sum."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import square"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 6
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"square.square(5)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 7,
"text": [
"25"
]
}
],
"prompt_number": 7
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import time"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 8
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"time"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 9,
"text": [
"<module 'time' from '/Users/anand/pyenvs/sandbox27/lib/python2.7/lib-dynload/time.so'>"
]
}
],
"prompt_number": 9
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"time.asctime"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 10,
"text": [
"<function time.asctime>"
]
}
],
"prompt_number": 10
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"time.asctime()"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 11,
"text": [
"'Fri Aug 2 12:41:21 2013'"
]
}
],
"prompt_number": 11
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"time.asctime()"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 12,
"text": [
"'Fri Aug 2 12:41:27 2013'"
]
}
],
"prompt_number": 12
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"%%file date.py\n",
"import time\n",
"print time.asctime()"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Writing date.py\n"
]
}
],
"prompt_number": 13
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"!python date.py"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Fri Aug 2 12:42:04 2013\r\n"
]
}
],
"prompt_number": 14
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"!python date.py"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Fri Aug 2 12:42:07 2013\r\n"
]
}
],
"prompt_number": 15
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Back to generators**"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"!python grep.py def grep.py"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"def grep(pattern, lines):\r\n",
"def uppercase(seq):\r\n",
"def print_lines(lines):\r\n",
"def main():\r\n"
]
}
],
"prompt_number": 20
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"%%file count_functions.py\n",
"import grep\n",
"import os\n",
"\n",
"def get_files(dir, suffix):\n",
" files = os.listdir(dir)\n",
" for f in files:\n",
" if f.endswith(suffix):\n",
" yield f\n",
"\n",
"def read_files(filenames):\n",
" for f in filenames:\n",
" for line in open(f):\n",
" yield line\n",
" \n",
"def main():\n",
" filenames = get_files(\".\", \".py\")\n",
" lines = read_files(filenames)\n",
" lines = grep.grep(\"def\", lines)\n",
" grep.print_lines(lines)\n",
" \n",
"if __name__ == \"__main__\":\n",
" main()"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Overwriting count_functions.py\n"
]
}
],
"prompt_number": 25
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"!python count_functions.py"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"def get_files(dir, suffix):\r\n",
"def read_files(filenames):\r\n",
"def main():\r\n",
" lines = grep.grep(\"def\", lines)\r\n",
"def grep(pattern, lines):\r\n",
"def uppercase(seq):\r\n",
"def print_lines(lines):\r\n",
"def main():\r\n",
"def square(x):\r\n"
]
}
],
"prompt_number": 26
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem:** Write a program `count_lines.py` to count number of lines in one or more files. The program should accept filenames as command line arguments.\n",
"\n",
" $ python count_lines.py a.txt b.txt\n",
" 23"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem:** Write a program `count_words.py` to count number of words in one or more files. The program should accept filenames as command line arguments.\n",
"\n",
" $ python count_words.py a.txt b.txt\n",
" 46"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"%%file count_lines.py\n",
"import sys\n",
"\n",
"def read_files(filenames):\n",
" for f in filenames:\n",
" for line in open(f):\n",
" yield line\n",
"\n",
"def count(it):\n",
" n = 0\n",
" for x in it:\n",
" n += 1\n",
" return n\n",
"\n",
"def main():\n",
" filenames = sys.argv[1:]\n",
" lines = read_files(filenames)\n",
" print count(lines)\n",
" \n",
"if __name__ == \"__main__\":\n",
" main()"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Overwriting count_lines.py\n"
]
}
],
"prompt_number": 28
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"!python count_lines.py date.py grep.py"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"28\r\n"
]
}
],
"prompt_number": 30
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"%%file count_words.py\n",
"import sys\n",
"from count_lines import read_files, count\n",
"\n",
"def split_words(lines):\n",
" for line in lines:\n",
" for w in line.strip().split():\n",
" yield w\n",
"\n",
"def main():\n",
" filenames = sys.argv[1:]\n",
" lines = read_files(filenames)\n",
" words = split_words(lines)\n",
" print count(words)\n",
" \n",
"if __name__ == \"__main__\":\n",
" main()"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Writing count_words.py\n"
]
}
],
"prompt_number": 32
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"!python count_words.py date.py grep.py"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"65\r\n"
]
}
],
"prompt_number": 33
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"!wc -w date.py grep.py"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
" 4 date.py\r\n",
" 61 grep.py\r\n",
" 65 total\r\n"
]
}
],
"prompt_number": 34
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Iterator/generator can be consumed only once."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = iter(range(5))\n",
"print next(x) # first element is consumed here\n",
"print list(x) # remaining all are consumed here\n",
"print list(x) # nothing left, so empty list"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"0\n",
"[1, 2, 3, 4]\n",
"[]\n"
]
}
],
"prompt_number": 36
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"How to look at an iterator without consuming it?"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def peep(it):\n",
" for x in it:\n",
" print x\n",
" yield x"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 37
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = iter(range(10))\n",
"y = list(peep(x))"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"0\n",
"1\n",
"2\n",
"3\n",
"4\n",
"5\n",
"6\n",
"7\n",
"8\n",
"9\n"
]
}
],
"prompt_number": 40
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"y"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 41,
"text": [
"[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]"
]
}
],
"prompt_number": 41
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Write a function `iterjoin`, that takes two iterators as arguments and returns a single iterator.\n",
"\n",
" >>> x = iter([1, 2, 3])\n",
" >>> y = iter([4, 5, 6])\n",
" >>> z = iterjoin(x, y)\n",
" >>> list(z)\n",
" [1, 2, 3, 4, 5, 6]"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def gen123():\n",
" yield 1\n",
" yield 2\n",
" yield 3\n",
" \n",
"g = gen123()"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 42
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"next(g)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 43,
"text": [
"1"
]
}
],
"prompt_number": 43
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Quick Intro to List Comprehensions**"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"[x*x for x in range(10)]"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 45,
"text": [
"[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]"
]
}
],
"prompt_number": 45
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"[x*x for x in range(10) if x%2 == 0]"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 46,
"text": [
"[0, 4, 16, 36, 64]"
]
}
],
"prompt_number": 46
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"[line for line in open(\"grep.py\") \n",
" if line.startswith(\"def\")]"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 48,
"text": [
"['def grep(pattern, lines):\\n',\n",
" 'def uppercase(seq):\\n',\n",
" 'def print_lines(lines):\\n',\n",
" 'def main():\\n']"
]
}
],
"prompt_number": 48
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"%%file a.csv\n",
"1,2,3\n",
"2,4,6\n",
"3,6,9"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Writing a.csv\n"
]
}
],
"prompt_number": 49
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"[line.strip().split(\",\") for line in open(\"a.csv\")]"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 52,
"text": [
"[['1', '2', '3'], ['2', '4', '6'], ['3', '6', '9']]"
]
}
],
"prompt_number": 52
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"%%file b.csv\n",
"# begin\n",
"1,2,3\n",
"2,4,6\n",
"# after two lines\n",
"3,6,9\n",
"#end"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Overwriting b.csv\n"
]
}
],
"prompt_number": 54
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Parse the above csv file by ignoring the lines starting with # character."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"sum([i*i for i in range(1, 101)])"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 55,
"text": [
"338350"
]
}
],
"prompt_number": 55
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def squares(numbers):\n",
" return [x*x for x in numbers]"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 56
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"squares(range(10))"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 57,
"text": [
"[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]"
]
}
],
"prompt_number": 57
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Generator Expressions**"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def squares(numbers):\n",
" return (x*x for x in numbers)"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 58
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"s = squares(range(10))\n",
"s"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 59,
"text": [
"<generator object <genexpr> at 0x102701c30>"
]
}
],
"prompt_number": 59
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"sum((x*x for x in range(1, 101)))"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 60,
"text": [
"338350"
]
}
],
"prompt_number": 60
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"sum(x*x for x in range(1, 101))"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 61,
"text": [
"338350"
]
}
],
"prompt_number": 61
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"sum(x*x for x in xrange(1000000))"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 62,
"text": [
"333332833333500000"
]
}
],
"prompt_number": 62
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def readlines(filenames):\n",
" return (line for f in filenames for line in open(f))\n",
"\n",
"def grep(pattern, lines):\n",
" return (line for line in lines if pattern in line)"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 63
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Implement `count` using generator expressions. The count function should take an iterator as argument and count the number of elements in it.\n",
"\n",
" >>> count(iter(range(10)))\n",
" 10\n",
" >>> count(iter(\"hello\"))\n",
" 5\n",
"\n",
"\n",
"Solution:\n",
"\n",
" def count(it):\n",
" return sum(1 for x in it)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Python module `itertools` has a function `izip`, that zips two iterators together and returns a new iterator.\n",
"\n",
" import itertools\n",
" for a, b in itertools.izip(\"hello\", \"world\"):\n",
" print a, b\n",
"\n",
"Can you implement izip yourself?\n",
"\n",
"Another sample use:\n",
"\n",
" z = izip(\"hello\", \"world\")\n",
" print next(z) # ('h', 'w')\n",
" print next(z) # ('e', 'o')"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"zip('hello', 'world')"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 64,
"text": [
"[('h', 'w'), ('e', 'o'), ('l', 'r'), ('l', 'l'), ('o', 'd')]"
]
}
],
"prompt_number": 64
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def izip(it1, it2):\n",
" it1 = iter(it1)\n",
" it2 = iter(it2)\n",
" while True:\n",
" yield next(it1), next(it2)\n",
" \n",
"\n",
"for a, b in izip(\"hello\", \"world\"):\n",
" print a, b"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"h w\n",
"e o\n",
"l r\n",
"l l\n",
"o d\n"
]
}
],
"prompt_number": 65
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## More on Functions"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def square(x): return x*x"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 67
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"f = square"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 68
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"f(4)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 69,
"text": [
"16"
]
}
],
"prompt_number": 69
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"max(1, 2, 3)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 70,
"text": [
"3"
]
}
],
"prompt_number": 70
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def my_max(*args):\n",
" m = args[0]\n",
" for a in args:\n",
" if a > m:\n",
" m = a\n",
" return m\n",
"\n",
"my_max(1, 2, 3)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 74,
"text": [
"3"
]
}
],
"prompt_number": 74
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem:** Write a function `my_sum`, which takes variable number of numbers as arguments and computes their sum.\n",
"\n",
" >>> my_sum(1)\n",
" 1\n",
" >>> my_sum(1, 2, 3)\n",
" 6\n",
" >>> my_sum(1, 2, 3, 4, 5)\n",
" 15"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Unpacking arguments\n",
"args = [1, 2, 5, 9, 3]\n",
"print my_max(*args)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"9\n"
]
}
],
"prompt_number": 78
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def add(a, b): return a + b\n",
"args = (1, 2)\n",
"print add(*args)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"3\n"
]
}
],
"prompt_number": 79
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def sprintf(template, *args):\n",
" return template % args\n",
"\n",
"print sprintf(\"hello %s\", \"python\")"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"hello python\n"
]
}
],
"prompt_number": 77
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\"chapter %d: %s\" % (1, \"Introduction\")"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 81,
"text": [
"'chapter 1: Introduction'"
]
}
],
"prompt_number": 81
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Keyword Arguments**"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import os\n",
"files = os.listdir(\".\")\n",
"print sorted(files)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"['.git', 'Advanced Python Workshop - Day 1.ipynb', 'Advanced Python Workshop - Day 2.ipynb', 'Advanced Python Workshop - Day 3.ipynb', 'Untitled0.ipynb', 'a.csv', 'b.csv', 'count_functions.py', 'count_lines.py', 'count_lines.pyc', 'count_words.py', 'date.py', 'echo.py', 'grep.py', 'grep.pyc', 'square.py', 'square.pyc']\n"
]
}
],
"prompt_number": 83
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def getext(filename):\n",
" return filename.split(\".\")[-1]\n",
"print sorted(files, key=getext)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"['a.csv', 'b.csv', '.git', 'Advanced Python Workshop - Day 1.ipynb', 'Advanced Python Workshop - Day 2.ipynb', 'Advanced Python Workshop - Day 3.ipynb', 'Untitled0.ipynb', 'count_functions.py', 'count_lines.py', 'count_words.py', 'date.py', 'echo.py', 'grep.py', 'square.py', 'count_lines.pyc', 'grep.pyc', 'square.pyc']\n"
]
}
],
"prompt_number": 84
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** How do you sort filenames by length of the filename?"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def diff(a, b):\n",
" return a - b\n",
"\n",
"print diff(5, 2)\n",
"print diff(5, b=2)\n",
"print diff(a=5, b=2)\n",
"print diff(b=2, a=5)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"3\n",
"3\n",
"3\n",
"3\n"
]
}
],
"prompt_number": 85
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def mydict(**kwargs):\n",
" return kwargs\n",
"\n",
"mydict(x=1, y=2)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 86,
"text": [
"{'x': 1, 'y': 2}"
]
}
],
"prompt_number": 86
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\"chapter %d: %s\" % (1, \"introduction\")"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 90,
"text": [
"'chapter 1: introduction'"
]
}
],
"prompt_number": 90
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\"chapter %(num)d: %(title)s\" % {\"num\": 1, \"title\": \"introduction\"}"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 91,
"text": [
"'chapter 1: introduction'"
]
}
],
"prompt_number": 91
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"t = \"chapter %(num)d: %(title)s\\n\\nWelcome to %(title)s\"\n",
"print t % {\"num\": 1, \"title\": \"introduction\"}"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"chapter 1: introduction\n",
"\n",
"Welcome to introduction\n"
]
}
],
"prompt_number": 93
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"%%file hello.tmpl\n",
"Hello, %(name)s"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Overwriting hello.tmpl\n"
]
}
],
"prompt_number": 94
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def render_template(_filename, **kwargs):\n",
" t = open(_filename).read()\n",
" return t % kwargs\n",
"\n",
"print render_template(\"hello.tmpl\", name=\"python\")"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Hello, python\n"
]
}
],
"prompt_number": 95
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem:** Implement render_template1 which takes arguments by position and substitutes them.\n",
"\n",
" print render_template1(\"a.tmpl\", \"hello\", \"world\")"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Lambda functions**"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"names = [\n",
" 'python', 'Perl', 'Java', \n",
" 'c', 'Haskell', 'ruby']\n",
"sorted(names)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 98,
"text": [
"['Haskell', 'Java', 'Perl', 'c', 'python', 'ruby']"
]
}
],
"prompt_number": 98
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"sorted(names, key=len)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 99,
"text": [
"['c', 'Perl', 'Java', 'ruby', 'python', 'Haskell']"
]
}
],
"prompt_number": 99
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"How to sort them ignoring the case?"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def lower(s): return s.lower()\n",
"sorted(names, key=lower)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 101,
"text": [
"['c', 'Haskell', 'Java', 'Perl', 'python', 'ruby']"
]
}
],
"prompt_number": 101
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"sorted(names, key=lambda s: s.lower())"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 102,
"text": [
"['c', 'Haskell', 'Java', 'Perl', 'python', 'ruby']"
]
}
],
"prompt_number": 102
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"square = lambda x: x*x\n",
"print square(4)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"16\n"
]
}
],
"prompt_number": 103
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"functions = {\n",
" \"square\": lambda x: x*x,\n",
" \"cube\": lambda x: x*x*x,\n",
" \"incr\": lambda x: x+1\n",
"}\n"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 105
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def call_func(name, arg):\n",
" f = functions[name]\n",
" return f(arg)\n",
"\n",
"call_func(\"incr\", 7)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 106,
"text": [
"8"
]
}
],
"prompt_number": 106
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Write a function `extsort` that takes list of filenames and sorts them by extension.\n",
"\n",
" >>> extsort(['a.py', 'b.py', 'x.c'])\n",
" ['x.c', 'a.py', 'b.py']"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def isort(values):\n",
" # you can define an inner function like this, if required.\n",
" def lower(s):\n",
" return s.lower()\n",
" return sorted(values, key=lower)"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 109
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"(lambda x:x*x)(4)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "pyout",
"prompt_number": 110,
"text": [
"16"
]
}
],
"prompt_number": 110
}
],
"metadata": {}
}
]
}
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