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Advanced Python TrainingDecember 13-14, 2013Global Analytics -- http://nbviewer.ipython.org/gist/anandology/7939444
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day2.ipynb
{
"metadata": {
"name": ""
},
"nbformat": 3,
"nbformat_minor": 0,
"worksheets": [
{
"cells": [
{
"cell_type": "markdown",
"metadata": {},
"source": [
"# Advanced Python Training - Day 2\n",
"December 13-14, 2013<br/>\n",
"Global Analytics"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import re\n",
"class Person(object):\n",
" def __init__(self, firstname, lastname):\n",
" self.firstname = firstname\n",
" self.lastname = lastname\n",
" self._phone = \"00000000\"\n",
" \n",
" @property\n",
" def fullname(self):\n",
" return self.firstname + \" \" + self.lastname\n",
" \n",
" def get_phone(self):\n",
" return self._phone\n",
" \n",
" def set_phone(self, value):\n",
" if not re.match(\"^[ 0-9-]+$\", value):\n",
" raise ValueError(\"Invalid phone number: %r\"% value)\n",
" self._phone = value\n",
" \n",
" phone = property(get_phone, set_phone)\n",
"\n",
"p = Person(\"Foo\", \"Bar\")\n",
"print p.fullname"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Foo Bar\n"
]
}
],
"prompt_number": 16
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"p.phone = \"not-a-number\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"ename": "ValueError",
"evalue": "Invalid phone number: 'not-a-number'",
"output_type": "pyerr",
"traceback": [
"\u001b[0;31m---------------------------------------------------------------------------\u001b[0m\n\u001b[0;31mValueError\u001b[0m Traceback (most recent call last)",
"\u001b[0;32m<ipython-input-17-dca623967e9e>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mp\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mphone\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;34m\"not-a-number\"\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
"\u001b[0;32m<ipython-input-16-8b87d2913e58>\u001b[0m in \u001b[0;36mphone\u001b[0;34m(self, value)\u001b[0m\n\u001b[1;32m 17\u001b[0m \u001b[0;32mdef\u001b[0m \u001b[0mphone\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m 18\u001b[0m \u001b[0;32mif\u001b[0m \u001b[0;32mnot\u001b[0m \u001b[0mre\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mmatch\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"^[ 0-9-]+$\"\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 19\u001b[0;31m \u001b[0;32mraise\u001b[0m \u001b[0mValueError\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"Invalid phone number: %r\"\u001b[0m\u001b[0;34m%\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m 20\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m_phone\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m 21\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n",
"\u001b[0;31mValueError\u001b[0m: Invalid phone number: 'not-a-number'"
]
}
],
"prompt_number": 17
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Add `url` property to the following class. The `url` of a post should be of the form `/yyyy/mm/dd/title-with-spaces-replaced-with-hyphens`\n",
"\n",
" class Post(object):\n",
" def __init__(self, year, month, day, title):\n",
" self.year = year\n",
" self.month = month\n",
" self.day = day\n",
" self.title = title\n",
" \n",
"Example:\n",
"\n",
" >>> p = Post(2013, 12, 7, \"hello world\")\n",
" >>> p.url\n",
" '/2013/12/07/hello-world'\n",
" >>> p.day = 9\n",
" >>> p.url\n",
" '/2013/12/09/hello-world'"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"!date"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Sat Dec 14 09:32:11 IST 2013\r\n"
]
}
],
"prompt_number": 18
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## WSGI"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"%%file hello_wsgi.py\n",
"\n",
"import wsgiref.simple_server\n",
"\n",
"def application(environ, start_response):\n",
" \"\"\"Simple WSGI application.\n",
" \"\"\"\n",
" print environ[\"REQUEST_METHOD\"], environ[\"PATH_INFO\"]\n",
" start_response(\"200 OK\", [(\"Content-type\", \"text/plain\")])\n",
" return [\"hello wsgi\\n\"]\n",
" \n",
"def run(host, port):\n",
" # Creating a server\n",
" # The server calls the application function for every request\n",
" server = wsgiref.simple_server.make_server(host, port, application)\n",
" print \"http://%s:%s/\" % (host, port)\n",
" \n",
" # go into infinite loop to serve requests\n",
" server.serve_forever()\n",
" \n",
"if __name__ == \"__main__\":\n",
" run(\"localhost\", 8080)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Overwriting hello_wsgi.py\n"
]
}
],
"prompt_number": 3
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Step1: lets create a Request class.\n",
"\n",
" class Request(object):\n",
" def __init__(self, environ):\n",
" self.environ = environ\n",
" \n",
" @property\n",
" def path(self):\n",
" return self.environ['PATH_INFO']\n",
" \n",
" "
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"%%file rajinikanth.py\n",
"\"\"\"A new web framework as smart as rajini kanth!\n",
"\"\"\"\n",
"import wsgiref.simple_server\n",
"\n",
"class Application(object):\n",
" def __init__(self):\n",
" self.url_mapping = []\n",
" self.after_request_func = None\n",
" \n",
" def run(self, host=\"0.0.0.0\", port=8080):\n",
" print \"run\"\n",
" server = wsgiref.simple_server.make_server(host, port, self)\n",
" print \"http://%s:%s/\" % (host, port)\n",
" server.serve_forever() \n",
" \n",
" def __call__(self, environ, start_response):\n",
" request = Request(environ)\n",
" start_response(\"200 OK\", [(\"Content-type\", \"text/plain\")])\n",
" \n",
" response = None\n",
" for path, func in self.url_mapping:\n",
" if path == request.path:\n",
" response = func(request)\n",
" break\n",
" \n",
" if not response:\n",
" response = \"Not Found\"\n",
" \n",
" if self.after_request_func:\n",
" response = self.after_request_func(response)\n",
" \n",
" return [response]\n",
" \n",
" def route(self, path):\n",
" def decorator(func):\n",
" self.url_mapping.append((path, func))\n",
" return func\n",
" return decorator\n",
" \n",
" def after_request(self, func):\n",
" self.after_request_func = func\n",
" return func\n",
" \n",
"\n",
"class Request(object):\n",
" def __init__(self, environ):\n",
" self.environ = environ\n",
" \n",
" @property\n",
" def path(self):\n",
" return self.environ['PATH_INFO']\n",
" "
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Overwriting rajinikanth.py\n"
]
}
],
"prompt_number": 5
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"%%file hello1.py\n",
"\n",
"from rajinikanth import Application\n",
"\n",
"app = Application()\n",
"\n",
"@app.after_request\n",
"def add_header(response):\n",
" return \"=======\\n\" + response + \"=========\\n\"\n",
"\n",
"#@app.route(\"/hello\")\n",
"def hello(request):\n",
" return \"Hello, world!\\n\"\n",
"decor = app.route(\"/hello\")\n",
"hello = decor(hello)\n",
"\n",
"\n",
"@app.route(\"/bye\")\n",
"def bye(request):\n",
" return \"Good bye!\\n\"\n",
"\n",
"if __name__ == \"__main__\":\n",
" app.run(\"localhost\", 7070)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Overwriting hello1.py\n"
]
}
],
"prompt_number": 4
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Old-style vs. new-style classes"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"class Old:\n",
" pass\n",
"\n",
"class New(object):\n",
" pass\n",
"\n",
"old = Old()\n",
"new = New()"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 8
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"type(old)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 9,
"text": [
"instance"
]
}
],
"prompt_number": 9
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"type(new)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 10,
"text": [
"__main__.New"
]
}
],
"prompt_number": 10
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"old.__len__ = lambda: 10\n",
"new.__len__ = lambda: 10"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 11
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"len(old)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 12,
"text": [
"10"
]
}
],
"prompt_number": 12
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"len(new)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"ename": "TypeError",
"evalue": "object of type 'New' has no len()",
"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-13-12fb657d434e>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mlen\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mnew\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
"\u001b[0;31mTypeError\u001b[0m: object of type 'New' has no len()"
]
}
],
"prompt_number": 13
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Descriptors**"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"class Person:\n",
" @property\n",
" def fullname(self):\n",
" return \"xxx\"\n",
" \n",
"p = Person()"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 16
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print p.fullname"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"xxx\n"
]
}
],
"prompt_number": 17
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"Person.fullname"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 18,
"text": [
"<property at 0x10360b890>"
]
}
],
"prompt_number": 18
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"p.__dict__"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 19,
"text": [
"{}"
]
}
],
"prompt_number": 19
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"Person.__dict__"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 20,
"text": [
"{'__doc__': None,\n",
" '__module__': '__main__',\n",
" 'fullname': <property at 0x10360b890>}"
]
}
],
"prompt_number": 20
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"dir(Person.fullname)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 21,
"text": [
"['__class__',\n",
" '__delattr__',\n",
" '__delete__',\n",
" '__doc__',\n",
" '__format__',\n",
" '__get__',\n",
" '__getattribute__',\n",
" '__hash__',\n",
" '__init__',\n",
" '__new__',\n",
" '__reduce__',\n",
" '__reduce_ex__',\n",
" '__repr__',\n",
" '__set__',\n",
" '__setattr__',\n",
" '__sizeof__',\n",
" '__str__',\n",
" '__subclasshook__',\n",
" 'deleter',\n",
" 'fdel',\n",
" 'fget',\n",
" 'fset',\n",
" 'getter',\n",
" 'setter']"
]
}
],
"prompt_number": 21
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"Person.fullname.__get__(p)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 22,
"text": [
"'xxx'"
]
}
],
"prompt_number": 22
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"class Constant(object):\n",
" def __init__(self, value):\n",
" self.value = value\n",
" \n",
" def __get__(self, obj, type=None):\n",
" print \"Constant.__get__\"\n",
" return self.value\n",
" \n",
" def __set__(self, obj, value):\n",
" raise Exception(\"Can't change a constant\")\n",
" \n",
"class Math(object):\n",
" pi = Constant(3.14)\n",
" \n",
"m = Math()\n",
"print m.pi\n",
"print m.pi"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Constant.__get__\n",
"3.14\n",
"Constant.__get__\n",
"3.14\n"
]
}
],
"prompt_number": 29
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"m.pi = 3"
],
"language": "python",
"metadata": {},
"outputs": [
{
"ename": "Exception",
"evalue": "Can't change a constant",
"output_type": "pyerr",
"traceback": [
"\u001b[0;31m---------------------------------------------------------------------------\u001b[0m\n\u001b[0;31mException\u001b[0m Traceback (most recent call last)",
"\u001b[0;32m<ipython-input-30-e238ec0b7a72>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mm\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mpi\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;36m3\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
"\u001b[0;32m<ipython-input-29-705c8de9ce8d>\u001b[0m in \u001b[0;36m__set__\u001b[0;34m(self, obj, value)\u001b[0m\n\u001b[1;32m 8\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m 9\u001b[0m \u001b[0;32mdef\u001b[0m \u001b[0m__set__\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mobj\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 10\u001b[0;31m \u001b[0;32mraise\u001b[0m \u001b[0mException\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"Can't change a constant\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m 11\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m 12\u001b[0m \u001b[0;32mclass\u001b[0m \u001b[0mMath\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mobject\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
"\u001b[0;31mException\u001b[0m: Can't change a constant"
]
}
],
"prompt_number": 30
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"It is a common pattern to lazily initialize some values and reuse them.\n",
"\n",
" class Posts(object):\n",
" def get_categories(self):\n",
" if self.categories is None:\n",
" self.categories = self._get_categories_from_db()\n",
" return self.categories\n",
"\n",
"Wouldn't it be nice if we can do it like:\n",
"\n",
" class Posts(object):\n",
" @lazy_property\n",
" def categories(self):\n",
" # get categories from db\n",
" return result\n",
" \n",
" \n",
" class Foo:\n",
" @lazy_proeperty\n",
" def db(self):\n",
" \"\"\"Connects to database and returns the database connection\"\"\"\n",
" print \"connecting to database\"\n",
" return \"dummy-connection\" # returning a dummy connection"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"A small clarification about decorators.\n",
"\n"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def foo(a):\n",
" return 1\n",
"\n",
"@foo\n",
"def square(x):\n",
" return x*x\n",
"\n",
"print square"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"1\n"
]
}
],
"prompt_number": 33
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"class Foo:\n",
" def __init__(self, x):\n",
" self.x = x\n",
" \n",
"@Foo\n",
"def square(x):\n",
" return x*x\n",
"\n",
"print square"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"<__main__.Foo instance at 0x103624b48>\n"
]
}
],
"prompt_number": 34
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Lets look at implementation of `property` descriptor."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"class my_property(object):\n",
" def __init__(self, getter):\n",
" print \"myproperty.__init__\", getter\n",
" self.getter = getter\n",
" \n",
" def __get__(self, obj, type):\n",
" if obj is None:\n",
" return self\n",
" print \"__get__\", obj, type\n",
" return self.getter(obj)\n",
" \n",
"class Person(object):\n",
" @my_property\n",
" def fullname(self):\n",
" return \"xxx\"\n",
" \n",
"p = Person()\n",
"print p.fullname"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"myproperty.__init__ <function fullname at 0x10361fd70>\n",
"__get__ <__main__.Person object at 0x103621bd0> <class '__main__.Person'>\n",
"xxx\n"
]
}
],
"prompt_number": 38
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"Person.fullname"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 39,
"text": [
"<__main__.my_property at 0x103627d90>"
]
}
],
"prompt_number": 39
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"%%file fs.py\n",
"\"\"\"\n",
"Implement files and directories as Python objects.\n",
"\n",
"1. f.size - should give size of the file\n",
"2. f.name - should give the name\n",
"3. f.abspath - should give absolute path of the file\n",
"4. f.read() - should read all the contents of the file\n",
"5. f.parent - should give the parent directory\n",
"6. d['a.py'] - should give File object corresponding to a.py\n",
"7. len(d) - should tell how many files are there in that directory\n",
"\n",
"Hints: see os and os.path modules\n",
"\"\"\"\n",
"import os.path\n",
"\n",
"class File(object):\n",
" def __init__(self, path):\n",
" self.path = path\n",
" \n",
" @property\n",
" def size(self):\n",
" return os.stat(self.path).st_size\n",
"\n",
"class Directory(File):\n",
" pass\n",
"\n",
"if __name__ == \"__main__\":\n",
" f = File(\"/tmp/a.py\")\n",
" assert f.name == \"a.py\"\n",
" assert f.abspath == \"/tmp/a.py\" \n",
" assert isinstance(f.parent, Directory)\n",
" assert f.parent.path == '/tmp'\n",
" assert f.parent['a.py'].name == 'a.py'\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Overwriting fs.py\n"
]
}
],
"prompt_number": 43
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Context Managers"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"with open(\"numbers.txt\") as f:\n",
" print f.read()"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"1 one\n",
"2 two\n",
"3 three\n",
"4 four\n",
"5 five\n"
]
}
],
"prompt_number": 44
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"dir(f)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 45,
"text": [
"['__class__',\n",
" '__delattr__',\n",
" '__doc__',\n",
" '__enter__',\n",
" '__exit__',\n",
" '__format__',\n",
" '__getattribute__',\n",
" '__hash__',\n",
" '__init__',\n",
" '__iter__',\n",
" '__new__',\n",
" '__reduce__',\n",
" '__reduce_ex__',\n",
" '__repr__',\n",
" '__setattr__',\n",
" '__sizeof__',\n",
" '__str__',\n",
" '__subclasshook__',\n",
" 'close',\n",
" 'closed',\n",
" 'encoding',\n",
" 'errors',\n",
" 'fileno',\n",
" 'flush',\n",
" 'isatty',\n",
" 'mode',\n",
" 'name',\n",
" 'newlines',\n",
" 'next',\n",
" 'read',\n",
" 'readinto',\n",
" 'readline',\n",
" 'readlines',\n",
" 'seek',\n",
" 'softspace',\n",
" 'tell',\n",
" 'truncate',\n",
" 'write',\n",
" 'writelines',\n",
" 'xreadlines']"
]
}
],
"prompt_number": 45
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"class DummyContext(object):\n",
" def __enter__(self):\n",
" print \"__enter__\"\n",
" return self\n",
" \n",
" def __exit__(self, type, exc, traceback):\n",
" print \"__exit__\", type, exc, traceback\n",
" return True\n",
" \n",
"with DummyContext() as d:\n",
" print d\n",
" raise Exception(\"foo\")"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"__enter__\n",
"<__main__.DummyContext object at 0x10362d450>\n",
"__exit__ <type 'exceptions.Exception'> foo <traceback object at 0x10362ad40>\n"
]
}
],
"prompt_number": 50
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import os\n",
"class chdir(object):\n",
" def __init__(self, path):\n",
" self.path = path\n",
" self.old_path = None\n",
" \n",
" def __enter__(self):\n",
" self.old_path = os.getcwd()\n",
" os.chdir(self.path)\n",
" \n",
" def __exit__(self, type, exc, traceback):\n",
" os.chdir(self.old_path)\n",
"\n",
"print os.getcwd()\n",
"with chdir(\"/tmp\"):\n",
" print os.getcwd()\n",
" print os.listdir(os.getcwd())\n",
"print os.getcwd()"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"/Users/anand/Dropbox/Trainings/2013/advancedpython-dec-ga/notebook\n",
"/private/tmp\n",
"['.s.PGSQL.5432', 'a.pl', 'icssuis501', 'launch-89nLgT', 'launch-rAjNNy', 'launch-rEQZsu', 'launchd-137.64Yecb', 'mobilepartner.pid', 'UTPS_OnlineUpdate_Mutex.pid']\n",
"/Users/anand/Dropbox/Trainings/2013/advancedpython-dec-ga/notebook\n"
]
}
],
"prompt_number": 54
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Implement a context manager `ignore_exception` that ignores all exceptions in that block.\n",
"\n",
" with ignore_exceptions():\n",
" open(\"no-such-file\").read()\n",
" print \"after with statement\""
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Class decorators**"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def logit(obj):\n",
" print \"created\", obj.__name__\n",
" return obj\n",
"\n",
"@logit\n",
"class A(object):\n",
" pass\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"created A\n"
]
}
],
"prompt_number": 55
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"A"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 56,
"text": [
"__main__.A"
]
}
],
"prompt_number": 56
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Meta Classes**"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print type(1)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"<type 'int'>\n"
]
}
],
"prompt_number": 57
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print type(int)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"<type 'type'>\n"
]
}
],
"prompt_number": 58
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print type(type)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"<type 'type'>\n"
]
}
],
"prompt_number": 59
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"class A(object): pass\n",
"a = A()"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 60
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"type(a)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 61,
"text": [
"__main__.A"
]
}
],
"prompt_number": 61
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"B = type(\"B\", (object,), {\"x\": 1})"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 62
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"B"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 63,
"text": [
"__main__.B"
]
}
],
"prompt_number": 63
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"B.x"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 64,
"text": [
"1"
]
}
],
"prompt_number": 64
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"B.__name__"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 65,
"text": [
"'B'"
]
}
],
"prompt_number": 65
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"class type2(type):\n",
" def __init__(self, name, bases, attrs):\n",
" type.__init__(self, name, bases, attrs)\n",
" print name, bases, attrs\n",
" \n",
"B2 = type2(\"B2\", (object,), {\"x\": 1})"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"B2 (<type 'object'>,) {'x': 1}\n"
]
}
],
"prompt_number": 66
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"B2"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 67,
"text": [
"__main__.B2"
]
}
],
"prompt_number": 67
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"type(B2)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 68,
"text": [
"__main__.type2"
]
}
],
"prompt_number": 68
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"class C2(B2):\n",
" pass"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"C2 (<class '__main__.B2'>,) {'__module__': '__main__'}\n"
]
}
],
"prompt_number": 69
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"class B3(object):\n",
" __metaclass__ = type2"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"B3 (<type 'object'>,) {'__module__': '__main__', '__metaclass__': <class '__main__.type2'>}\n"
]
}
],
"prompt_number": 70
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"type(B3)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 71,
"text": [
"__main__.type2"
]
}
],
"prompt_number": 71
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"class C3(B3): pass"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"C3 (<class '__main__.B3'>,) {'__module__': '__main__'}\n"
]
}
],
"prompt_number": 72
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"class LoggingMeta(type):\n",
" def __init__(self, name, bases, attrs):\n",
" type.__init__(self, name, bases, attrs)\n",
" print \"creating class\", name"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 73
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"class A(object):\n",
" __metaclass__ = LoggingMeta\n",
" "
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"creating class A\n"
]
}
],
"prompt_number": 74
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"class B(A): pass"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"creating class B\n"
]
}
],
"prompt_number": 75
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"%%file urls2.py\n",
"\n",
"urls = []\n",
"\n",
"class metapage(type):\n",
" def __init__(self, name, bases, attrs):\n",
" type.__init__(self, name, bases, attrs)\n",
" path = attrs.get(\"path\", \"/\" + name)\n",
" urls.append((path, self))\n",
" \n",
"class page(object):\n",
" __metaclass__ = metapage\n",
" \n",
"# get rid of page class from urls\n",
"urls = []\n",
" \n",
"class hello(page):\n",
" def GET(self):\n",
" return \"hello world!\"\n",
" \n",
"class bye(page):\n",
" path = \"/goodbye\"\n",
" def GET(self):\n",
" return \"good bye!\"\n",
" \n",
"print urls"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Overwriting urls2.py\n"
]
}
],
"prompt_number": 83
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"!python urls2.py"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"[('/hello', <class '__main__.hello'>), ('/goodbye', <class '__main__.bye'>)]\r\n"
]
}
],
"prompt_number": 84
},
{
"cell_type": "code",
"collapsed": false,
"input": [],
"language": "python",
"metadata": {},
"outputs": []
}
],
"metadata": {}
}
]
}
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