Python snippets

snippet.ipynb

{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "empty\n"
     ]
    }
   ],
   "source": [
    "# Check if list is empty\n",
    "li=[]\n",
    "\n",
    "if not li:\n",
    "    print 'empty'"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0000012345\n",
      "000123.456\n"
     ]
    }
   ],
   "source": [
    "# left padding zeros for readability\n",
    "print \"12345\".zfill(10)\n",
    "print str(123.456).zfill(10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'a': 1, 'b': 10, 'c': 11}"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# merging two dictionaries (b 10 should overwrite b 2)\n",
    "x = {'a':1, 'b': 2}\n",
    "y = {'b':10, 'c': 11}\n",
    "z = dict(x.items() + y.items())\n",
    "z"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[1, 2, 3, [4, 5]]\n",
      "[1, 2, 3, 4, 5]\n"
     ]
    }
   ],
   "source": [
    "# append vs extend\n",
    "x = [1, 2, 3]\n",
    "x.append([4, 5])\n",
    "print (x)\n",
    "\n",
    "x = [1, 2, 3]\n",
    "x.extend([4, 5])\n",
    "print (x)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0\n",
      "pizza\n"
     ]
    }
   ],
   "source": [
    "# list to dictionary using enumerate\n",
    "choices = ['pizza', 'pasta', 'salad', 'nachos']\n",
    "x =list(enumerate(choices))\n",
    "x\n",
    "print x[0][0]\n",
    "print x[0][1]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0 a\n",
      "1 b\n",
      "2 c\n",
      "3 d\n"
     ]
    }
   ],
   "source": [
    "# enumerate example 2\n",
    "mylist = [\"a\",\"b\",\"c\",\"d\"]\n",
    "for i,j in enumerate(mylist):\n",
    "    print i,j"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]\n",
      "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]\n",
      "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]\n",
      "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]\n",
      "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]\n",
      "[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]\n"
     ]
    }
   ],
   "source": [
    "# slicing\n",
    "a= range(0,10)\n",
    "b=a[0:10]\n",
    "c=a[0:]   \n",
    "d=a[:10]     \n",
    "e=a[:]\n",
    "f=a[::-1]\n",
    "print a\n",
    "print b\n",
    "print c\n",
    "print d\n",
    "print e\n",
    "print f"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "deque([1, 2, 3, 4, 5])\n",
      "deque([5, 1, 2, 3, 4])\n",
      "deque([3, 4, 5, 1, 2])\n",
      "deque([4, 5, 1, 2, 3])\n"
     ]
    }
   ],
   "source": [
    "#circular list and circular movement\n",
    "import collections\n",
    "l = collections.deque([1,2,3,4,5])\n",
    "l.rotate(0)\n",
    "print l\n",
    "l.rotate(1)\n",
    "print l\n",
    "l.rotate(2)\n",
    "print l\n",
    "l.rotate(-1)\n",
    "print l"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[[10, 11, 12, 13, 14, 15, 16, 17, 18, 19],\n",
      " [20, 21, 22, 23, 24, 25, 26, 27, 28, 29],\n",
      " [30, 31, 32, 33, 34, 35, 36, 37, 38, 39],\n",
      " [40, 41, 42, 43, 44, 45, 46, 47, 48, 49],\n",
      " [50, 51, 52, 53, 54, 55, 56, 57, 58, 59],\n",
      " [60, 61, 62, 63, 64, 65, 66, 67, 68, 69],\n",
      " [70, 71, 72, 73, 74]]\n"
     ]
    }
   ],
   "source": [
    "#produce even chunks of data\n",
    "def chunks(l, n):\n",
    "    \"\"\"Yield successive n-sized chunks from l.\"\"\"\n",
    "    for i in xrange(0, len(l), n):\n",
    "        yield l[i:i+n]\n",
    "\n",
    "import pprint\n",
    "pprint.pprint(list(chunks(range(10, 75), 10)))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[1, 2, 3, 4, 5, 6, 7, 8, 9]\n",
      "[1, 2, 3, 4, 5, 6, 7, 8, 9]\n"
     ]
    }
   ],
   "source": [
    "# merging mutiple lists into 1\n",
    "l = [[1,2,3],[4,5,6], [7], [8,9]]\n",
    "ll=sum(l, [])\n",
    "print ll\n",
    "lll=reduce(lambda x,y: x+y,l)\n",
    "print lll"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "c\n"
     ]
    }
   ],
   "source": [
    "# random selection from a list\n",
    "import random\n",
    "foo = ['a', 'b', 'c', 'd', 'e']\n",
    "print(random.choice(foo))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[{'age': 100, 'name': 'Bart'}, {'age': 39, 'name': 'Homer'}]\n",
      "[{'age': 39, 'name': 'Homer'}, {'age': 100, 'name': 'Bart'}]\n"
     ]
    }
   ],
   "source": [
    "# sort dictionary by value instead of key\n",
    "c =[{'name':'Homer', 'age':39}, {'name':'Bart', 'age':100}]\n",
    "newlist = sorted(c, key=lambda k: k['name'])\n",
    "print newlist\n",
    "newlist = sorted(c, key=lambda k: k['age'])\n",
    "print newlist"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "ename": "SyntaxError",
     "evalue": "invalid syntax (<ipython-input-14-b7781d56cd36>, line 4)",
     "output_type": "error",
     "traceback": [
      "\u001b[1;36m  File \u001b[1;32m\"<ipython-input-14-b7781d56cd36>\"\u001b[1;36m, line \u001b[1;32m4\u001b[0m\n\u001b[1;33m    or\u001b[0m\n\u001b[1;37m     ^\u001b[0m\n\u001b[1;31mSyntaxError\u001b[0m\u001b[1;31m:\u001b[0m invalid syntax\n"
     ]
    }
   ],
   "source": [
    "#copying a file in python\n",
    "import shutil\n",
    "shutil.copy2('/dir/file.ext', '/new/dir')\n",
    "or\n",
    "copyfile(src, dst)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "#switch statement in python\n",
    "def f(x):\n",
    "    return {\n",
    "        'a': 1,\n",
    "        'b': 2,\n",
    "    }.get(x, 9)    # 9 is default if x not found"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "<type 'dict'>\n",
      "<type 'list'>\n"
     ]
    }
   ],
   "source": [
    "#determine type of an object\n",
    "type([]) is list\n",
    "type({}) is dict\n",
    "type('') is str\n",
    "type(0) is int\n",
    "print type({})\n",
    "print type([])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Chained comparison operators work! \n",
      "Chained comparison operators work! \n",
      "Chained comparison operators work! \n",
      "\n"
     ]
    }
   ],
   "source": [
    "#chained comaprison\n",
    "mynumber = 3\n",
    "\n",
    "if 4 > mynumber > 2:\n",
    "    print(\"Chained comparison operators work! \\n\" * 3)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "height missing?\n",
      "\n"
     ]
    }
   ],
   "source": [
    "# dict default if key missing\n",
    "my_dict = {'name': 'Lancelot', 'quest': 'Holy Grail', 'favourite_color': 'blue'}\n",
    "print(my_dict.get('height', 'height missing?\\n'))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 19,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "('quest', 'Holy Grail')\n",
      "('name', 'Lancelot')\n",
      "('favourite_color', 'blue')\n"
     ]
    }
   ],
   "source": [
    "# dict iter items, similar to enumerate for lists\n",
    "for key, value in my_dict.iteritems():\n",
    "    print(key, value)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 20,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'even'"
      ]
     },
     "execution_count": 20,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# ternary operator\n",
    "b = 4\n",
    "x = 'odd' if b%2 ==1 else 'even'\n",
    "x"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 21,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "['a', 'b', 'd']\n",
      "['b', 'd']\n"
     ]
    }
   ],
   "source": [
    "#pop usage\n",
    "a = ['a', 'b', 'c', 'd']\n",
    "a.pop(-2)\n",
    "print a\n",
    "a.pop(0)\n",
    "print a"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 22,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['alabaster==0.7.3',\n",
       " 'argcomplete==0.8.9',\n",
       " 'astropy==1.0.3',\n",
       " 'babel==1.3',\n",
       " 'backports.ssl-match-hostname==3.4.0.2',\n",
       " 'bcolz==0.9.0',\n",
       " 'beautifulsoup4==4.3.2',\n",
       " 'binstar==0.11.0',\n",
       " 'bitarray==0.8.1',\n",
       " 'blaze==0.8.0',\n",
       " 'blz==0.6.2',\n",
       " 'bokeh==0.9.0',\n",
       " 'boto==2.38.0',\n",
       " 'bottleneck==1.0.0',\n",
       " 'cdecimal==2.3',\n",
       " 'certifi==14.5.14',\n",
       " 'cffi==1.1.0',\n",
       " 'clyent==0.3.4',\n",
       " 'colorama==0.3.3',\n",
       " 'conda-build==1.14.1',\n",
       " 'conda-env==2.4.2',\n",
       " 'conda==3.16.0',\n",
       " 'configobj==5.0.6',\n",
       " 'cryptography==0.9.1',\n",
       " 'cython==0.22.1',\n",
       " 'cytoolz==0.7.3',\n",
       " 'datashape==0.4.5',\n",
       " 'decorator==3.4.2',\n",
       " 'docutils==0.12',\n",
       " 'enum34==1.0.4',\n",
       " 'fastcache==1.0.2',\n",
       " 'flask==0.10.1',\n",
       " 'funcsigs==0.4',\n",
       " 'future==0.15.0',\n",
       " 'gevent-websocket==0.9.3',\n",
       " 'gevent==1.0.1',\n",
       " 'greenlet==0.4.7',\n",
       " 'grin==1.2.1',\n",
       " 'h5py==2.5.0',\n",
       " 'idna==2.0',\n",
       " 'ipaddress==1.0.7',\n",
       " 'ipython==3.2.1',\n",
       " 'itsdangerous==0.24',\n",
       " 'jdcal==1.0',\n",
       " 'jedi==0.8.1',\n",
       " 'jinja2==2.8',\n",
       " 'jsonschema==2.4.0',\n",
       " 'llvmlite==0.5.0',\n",
       " 'lxml==3.4.4',\n",
       " 'markupsafe==0.23',\n",
       " 'matplotlib==1.4.3',\n",
       " 'menuinst==1.0.4',\n",
       " 'mistune==0.7',\n",
       " 'mock==1.0.1',\n",
       " 'multipledispatch==0.4.7',\n",
       " 'networkx==1.9.1',\n",
       " 'nltk==3.0.3',\n",
       " 'nose==1.3.7',\n",
       " 'numba==0.19.1',\n",
       " 'numexpr==2.4.3',\n",
       " 'numpy==1.9.2',\n",
       " 'odo==0.3.2',\n",
       " 'openpyxl==1.8.5',\n",
       " 'pandas==0.16.2',\n",
       " 'patsy==0.3.0',\n",
       " 'pep8==1.6.2',\n",
       " 'pillow==2.8.2',\n",
       " 'pip==7.1.2',\n",
       " 'ply==3.6',\n",
       " 'psutil==2.2.1',\n",
       " 'py==1.4.27',\n",
       " 'pyaml==15.8.2',\n",
       " 'pyasn1==0.1.7',\n",
       " 'pycosat==0.6.1',\n",
       " 'pycparser==2.14',\n",
       " 'pycrypto==2.6.1',\n",
       " 'pyexcel-io==0.0.6',\n",
       " 'pyexcel-xls==0.0.7',\n",
       " 'pyexcel==0.1.7',\n",
       " 'pyflakes==0.9.2',\n",
       " 'pygments==2.0.2',\n",
       " 'pyopenssl==0.15.1',\n",
       " 'pyparsing==2.0.3',\n",
       " 'pyreadline==2.0',\n",
       " 'pytest==2.7.1',\n",
       " 'python-dateutil==2.4.2',\n",
       " 'pytz==2015.4',\n",
       " 'pywin32==219',\n",
       " 'pyyaml==3.11',\n",
       " 'pyzmq==14.7.0',\n",
       " 'requests==2.7.0',\n",
       " 'rope==0.9.4',\n",
       " 'runipy==0.1.3',\n",
       " 'scikit-image==0.11.3',\n",
       " 'scikit-learn==0.16.1',\n",
       " 'scipy==0.15.1',\n",
       " 'selenium==2.47.1',\n",
       " 'setuptools==18.1',\n",
       " 'six==1.9.0',\n",
       " 'snowballstemmer==1.2.0',\n",
       " 'sockjs-tornado==1.0.1',\n",
       " 'sphinx-rtd-theme==0.1.7',\n",
       " 'sphinx==1.3.1',\n",
       " 'spyder==2.3.5.2',\n",
       " 'sqlalchemy==1.0.5',\n",
       " 'statsmodels==0.6.1',\n",
       " 'sympy==0.7.6',\n",
       " 'tables==3.2.0',\n",
       " 'texttable==0.8.3',\n",
       " 'toolz==0.7.2',\n",
       " 'tornado==4.2.1',\n",
       " 'ujson==1.33',\n",
       " 'unicodecsv==0.9.4',\n",
       " 'werkzeug==0.10.4',\n",
       " 'wheel==0.24.0',\n",
       " 'xlrd==0.9.3',\n",
       " 'xlsxwriter==0.7.3',\n",
       " 'xlwings==0.3.5',\n",
       " 'xlwt-future==0.8.0',\n",
       " 'xlwt==1.0.0']"
      ]
     },
     "execution_count": 22,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "#get a list of all librarires installed\n",
    "import pip\n",
    "sorted([\"%s==%s\" % (i.key, i.version) for i in pip.get_installed_distributions()])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "0"
      ]
     },
     "execution_count": 23,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "#clear screen\n",
    "import os\n",
    "os.system('cls')\n",
    "#os.system('clear') in unix"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 24,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "empty\n",
      "0000012345\n"
     ]
    }
   ],
   "source": [
    "#run python program from python shell\n",
    "import os;execfile('C:\\Users\\Pinupols\\Desktop\\py_code\\onetime.py')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "3 1 6 [1, 2, 3]\n",
      "set([2, 3])\n",
      "set([1, 2, 3, 4])\n",
      "set([4])\n",
      "set([1, 4])\n"
     ]
    }
   ],
   "source": [
    "#set operations\n",
    "#from sets import Set\n",
    "s= [1,2,3]\n",
    "t= [2,3,4]\n",
    "print max(s),min(s),sum(s),sorted(s)\n",
    "print set(s).intersection(t)\n",
    "print set(s).union(t)\n",
    "print set(t)-set(s)\n",
    "print set(s).symmetric_difference(t)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": []
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "Python 2",
   "language": "python",
   "name": "python2"
  },
  "language_info": {
   "codemirror_mode": {
    "name": "ipython",
    "version": 2
   },
   "file_extension": ".py",
   "mimetype": "text/x-python",
   "name": "python",
   "nbconvert_exporter": "python",
   "pygments_lexer": "ipython2",
   "version": "2.7.10"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 0
}