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Notes from python training at LinkedIn (Jan 28-Jan30, 2014) - http://nbviewer.ipython.org/gist/anandology/8663909/
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day1.ipynb
{
"metadata": {
"name": ""
},
"nbformat": 3,
"nbformat_minor": 0,
"worksheets": [
{
"cells": [
{
"cell_type": "markdown",
"metadata": {},
"source": [
"# Python Training at LinkedIn - Day 1\n",
"\n",
"Jan 28-30, 2014 - [Anand Chitipothu](http://anandology.com)"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print \"Good Morning!\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Good Morning!\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"3 + 4"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 2,
"text": [
"7"
]
}
],
"prompt_number": 2
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"You can also write the python program in a file and run it as a script."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"%%file a.py\n",
"print 3 + 4"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Overwriting a.py\n"
]
}
],
"prompt_number": 3
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"!python a.py"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"7\r\n"
]
}
],
"prompt_number": 4
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Variables**"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"There is no need to declare variables up-front. You can start using them as and when needed."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = 5\n",
"print x*x"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"25\n"
]
}
],
"prompt_number": 5
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"And there is no need to tell Python what type it is."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = \"hello\"\n",
"print x"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"hello\n"
]
}
],
"prompt_number": 6
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Python is strongly-typed. It is an error to add a number to a string. No implicit conversion is done."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"1 + \"3\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"ename": "TypeError",
"evalue": "unsupported operand type(s) for +: 'int' and 'str'",
"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-a9d4b5316843>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0;36m1\u001b[0m \u001b[0;34m+\u001b[0m \u001b[0;34m\"3\"\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
"\u001b[0;31mTypeError\u001b[0m: unsupported operand type(s) for +: 'int' and 'str'"
]
}
],
"prompt_number": 7
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"If you use an undefined variable, it is an error."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# y is not defined here\n",
"x + y"
],
"language": "python",
"metadata": {},
"outputs": [
{
"ename": "NameError",
"evalue": "name 'y' is not defined",
"output_type": "pyerr",
"traceback": [
"\u001b[0;31m---------------------------------------------------------------------------\u001b[0m\n\u001b[0;31mNameError\u001b[0m Traceback (most recent call last)",
"\u001b[0;32m<ipython-input-10-c74b59957f6e>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[1;32m 1\u001b[0m \u001b[0;31m# y is not defined here\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 2\u001b[0;31m \u001b[0mx\u001b[0m \u001b[0;34m+\u001b[0m \u001b[0my\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
"\u001b[0;31mNameError\u001b[0m: name 'y' is not defined"
]
}
],
"prompt_number": 10
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"And it is possible to assign multiple values at once."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"a, b = 1, 2\n",
"print a\n",
"print b"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"1\n",
"2\n"
]
}
],
"prompt_number": 11
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"How do you swap values of two variables?"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"tmp = a\n",
"b = a\n",
"a = tmp\n",
"print a, b"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"1 1\n"
]
}
],
"prompt_number": 12
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"a, b = 1, 2"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 14
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"a, b = b, a"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 15
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print a, b"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"2 1\n"
]
}
],
"prompt_number": 16
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Functions"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = 4\n",
"print x*x"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"16\n"
]
}
],
"prompt_number": 17
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def square(x):\n",
" return x*x\n",
"\n",
"print square(4)\n",
"print square(2+3)\n",
"print square(square(2))"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"16\n",
"25\n",
"16\n"
]
}
],
"prompt_number": 18
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Write a function `cube` to compute cube of a number.\n",
"\n",
" >>> cube(2)\n",
" 8\n",
" >>> cube(3)\n",
" 27"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"square(5)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 19,
"text": [
"25"
]
}
],
"prompt_number": 19
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"square"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 20,
"text": [
"<function __main__.square>"
]
}
],
"prompt_number": 20
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"f = square\n",
"print f(5)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"25\n"
]
}
],
"prompt_number": 21
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"f"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 22,
"text": [
"<function __main__.square>"
]
}
],
"prompt_number": 22
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def sum_of_squares(x, y):\n",
" return square(x) + square(y)"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 23
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"sum_of_squares(3, 4)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 24,
"text": [
"25"
]
}
],
"prompt_number": 24
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"How to implement `sum_of_cubes`?"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def cube(x):\n",
" return x*x*x"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 25
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def sum_of_cubes(x, y):\n",
" return cube(x) + cube(y)"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 26
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print sum_of_cubes(3, 4)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"91\n"
]
}
],
"prompt_number": 27
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"You can pass function as argument too."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def sumof(f, x, y):\n",
" return f(x) + f(y)\n",
"\n",
"print sumof(square, 3, 4)\n",
"print sumof(cube, 3, 4)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"25\n",
"91\n"
]
}
],
"prompt_number": 28
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Built-in Functions**"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"min(3, 4)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 29,
"text": [
"3"
]
}
],
"prompt_number": 29
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"max(4, 6)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 30,
"text": [
"6"
]
}
],
"prompt_number": 30
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"len(\"helloworld\")"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 31,
"text": [
"10"
]
}
],
"prompt_number": 31
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\"hello\" + str(1)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 32,
"text": [
"'hello1'"
]
}
],
"prompt_number": 32
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"int(\"3\") + 2"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 33,
"text": [
"5"
]
}
],
"prompt_number": 33
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Write a function `count_digits` to count number of digits in a given number.\n",
" \n",
" >>> count_digits(5)\n",
" 1\n",
" >>> count_digits(12345)\n",
" 5\n",
" \n",
"Hint: Use built-in function `str`."
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Built-in function `help` shows help on a function or a module."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"help(min)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Help on built-in function min in module __builtin__:\n",
"\n",
"min(...)\n",
" min(iterable[, key=func]) -> value\n",
" min(a, b, c, ...[, key=func]) -> value\n",
" \n",
" With a single iterable argument, return its smallest item.\n",
" With two or more arguments, return the smallest argument.\n",
"\n"
]
}
],
"prompt_number": 36
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**print vs. return**"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Lets look at the following 2 functions."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def square1(x):\n",
" print x*x\n",
"\n",
"square1(4)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"16\n"
]
}
],
"prompt_number": 38
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def square2(x):\n",
" return x*x\n",
"\n",
"print square2(4)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"16\n"
]
}
],
"prompt_number": 39
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"What is the difference between these two? Which one is better and why?"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"How do you compute square of square of a number?"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"square2(square2(2))"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 40,
"text": [
"16"
]
}
],
"prompt_number": 40
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"You can't do that with `square1`."
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### Methods"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Methods are functions that operate on an object."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = \"hello\"\n",
"print x.upper()"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"HELLO\n"
]
}
],
"prompt_number": 41
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\"Hello\".lower()"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 45,
"text": [
"'hello'"
]
}
],
"prompt_number": 45
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\"mathematics\".count(\"mat\")"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 42,
"text": [
"2"
]
}
],
"prompt_number": 42
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\"Mathematics\".count(\"mat\")"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 44,
"text": [
"1"
]
}
],
"prompt_number": 44
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Write a function `icount` to count number of occurances of a substring in the given string, ignoring the case.\n",
"\n",
" >>> icount(\"mathematics\", \"mat\")\n",
" 2\n",
" >>> icount(\"Mathematics\", \"mat\")\n",
" 2\n",
" >>> icount(\"Mathematics\", \"MAT\")\n",
" 2"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Conditional Expressions"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"age = 30\n",
"print age > 20"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"True\n"
]
}
],
"prompt_number": 46
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print age < 20"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"False\n"
]
}
],
"prompt_number": 47
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"age == 30"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 48,
"text": [
"True"
]
}
],
"prompt_number": 48
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"age != 25"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 49,
"text": [
"True"
]
}
],
"prompt_number": 49
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\"python\" == \"python\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 50,
"text": [
"True"
]
}
],
"prompt_number": 50
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\"python\" > \"perl\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 51,
"text": [
"True"
]
}
],
"prompt_number": 51
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\"python\" > \"java\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 52,
"text": [
"True"
]
}
],
"prompt_number": 52
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\"python\" > \"zoo\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 53,
"text": [
"False"
]
}
],
"prompt_number": 53
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"not \"python\" > \"zoo\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 54,
"text": [
"True"
]
}
],
"prompt_number": 54
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"name = \"joe\"\n",
"age = 25"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 55
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"name == \"joe\" and age > 20"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 56,
"text": [
"True"
]
}
],
"prompt_number": 56
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Wrtite a function `istreq` to test if 2 strings are equal ignoring the case.\n",
"\n",
" >>> istreq(\"python\", \"PYTHON\")\n",
" True\n",
" "
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Python has `in` and `not in` operators for testing for contains. "
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\"man\" in \"woman\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 57,
"text": [
"True"
]
}
],
"prompt_number": 57
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\"hell\" in \"hello\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 58,
"text": [
"True"
]
}
],
"prompt_number": 58
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\"el\" in \"hello\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 59,
"text": [
"True"
]
}
],
"prompt_number": 59
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## If Statement"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"n = 26\n",
"if n % 2 == 0:\n",
" print \"even\"\n",
"else:\n",
" print \"odd\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"even\n"
]
}
],
"prompt_number": 62
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Write a function `minimum` to compute minimum of given 2 numbers. Do it without using the built-in `min` function.\n",
"\n",
" >>> minimum(3, 6)\n",
" 3\n",
" >>> minimum(7, 4)\n",
" 4"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Write a function `minimum3` to compute minimum of 3 numbers. Can you use the above `minimum` function in implementing this?\n",
"\n",
" >>> minimum3(4, 9, 2)\n",
" 2"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Solutions to above problems:"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def minimum(x, y):\n",
" if x < y:\n",
" return x\n",
" else:\n",
" return y\n",
" \n",
"print minimum(3, 5)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"3\n"
]
}
],
"prompt_number": 63
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def minimum3(x, y, z):\n",
" m = minimum(x, y)\n",
" return minimum(m, z)\n",
" # return minimum(minimum(x, y), z)"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 64
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Lists"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = [\"a\", \"b\", \"c\"]"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 71
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print x"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"['a', 'b', 'c']\n"
]
}
],
"prompt_number": 72
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"len(x)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 73,
"text": [
"3"
]
}
],
"prompt_number": 73
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x[0]"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 74,
"text": [
"'a'"
]
}
],
"prompt_number": 74
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x[1]"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 75,
"text": [
"'b'"
]
}
],
"prompt_number": 75
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x[2]"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 76,
"text": [
"'c'"
]
}
],
"prompt_number": 76
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x[3]"
],
"language": "python",
"metadata": {},
"outputs": [
{
"ename": "IndexError",
"evalue": "list index out of range",
"output_type": "pyerr",
"traceback": [
"\u001b[0;31m---------------------------------------------------------------------------\u001b[0m\n\u001b[0;31mIndexError\u001b[0m Traceback (most recent call last)",
"\u001b[0;32m<ipython-input-77-ed224ad0520d>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mx\u001b[0m\u001b[0;34m[\u001b[0m\u001b[0;36m3\u001b[0m\u001b[0;34m]\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
"\u001b[0;31mIndexError\u001b[0m: list index out of range"
]
}
],
"prompt_number": 77
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Modules"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import time"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 78
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"That imported the time module in to current namespace."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"time"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 79,
"text": [
"<module 'time' from '/Users/anand/pyenvs/sandbox27/lib/python2.7/lib-dynload/time.so'>"
]
}
],
"prompt_number": 79
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"time.asctime()"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 80,
"text": [
"'Tue Jan 28 11:48:04 2014'"
]
}
],
"prompt_number": 80
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Write a program `date.py` that prints the current date and time."
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Reading command-line arguments**"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"%%file args.py\n",
"import sys\n",
"print sys.argv"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Writing args.py\n"
]
}
],
"prompt_number": 81
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"!python args.py"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"['args.py']\r\n"
]
}
],
"prompt_number": 82
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"!python args.py hello"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"['args.py', 'hello']\r\n"
]
}
],
"prompt_number": 83
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"!python args.py hello world"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"['args.py', 'hello', 'world']\r\n"
]
}
],
"prompt_number": 84
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Write program `echo.py` that takes one argument from the command line and prints it back.\n",
"\n",
"<pre>\n",
"$ python echo.py hello\n",
"hello\n",
"$ python echo.py hello world\n",
"hello\n",
"</pre>"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem:** Write program `square.py` that takes a number as command-line argument and prints its square.\n",
"\n",
"<pre>\n",
"$ python square.py 5\n",
"25\n",
"$ python square.py 4\n",
"16\n",
"</pre>"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem:** Write a program `add.py` that takes 2 numbers as command line arguments and prints their sum.\n",
"\n",
"<pre>\n",
"$ python add.py 2 3\n",
"5\n",
"</pre>"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## For Loop"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = [\"a\", \"b\", \"c\"]\n",
"for a in x:\n",
" print a"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"a\n",
"b\n",
"c\n"
]
}
],
"prompt_number": 85
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Write a function `my_sum` that takes a list of numbers as argument and returns their sum.\n",
" \n",
" >>> my_sum([1, 2, 3, 4, 5])\n",
" 15\n",
" \n",
"Note: You should do this without using the built-in `sum` function."
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Appending new elements to a list**"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"The `append` method is used to add new elements to a list at the end."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = [\"a\", \"b\", \"c\"]\n",
"x.append(\"d\")\n",
"print x"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"['a', 'b', 'c', 'd']\n"
]
}
],
"prompt_number": 87
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Write a function `squares` that takes a list of numbers as arguments and returns a new list containing their squares.\n",
"\n",
" >>> squares([1, 2, 3, 4, 5])\n",
" [1, 4, 9, 16, 25]"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Write a function `evens` that takes a list of numbers as argument and returns a list containing only the even numbers from the given list.\n",
"\n",
" >>> evens([1, 2, 3, 4, 5, 6, 7, 8])\n",
" [2, 4, 6, 8]"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Write a function `xmap` to take a function `f` and a list of values and returns a list containing result of `f` applied to each value in the list.\n",
"\n",
" >>> xmap(square, [1, 2, 3, 4])\n",
" [1, 4, 9, 16]\n",
" >>> xmap(cube, [1, 2, 3, 4])\n",
" [1, 8, 27, 64]\n",
" "
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Pitfalls in modifying lists**"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = [1, 2, 3, 4]\n",
"y = x\n",
"x.append(5)\n",
"print x\n",
"print y"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"[1, 2, 3, 4, 5]\n",
"[1, 2, 3, 4, 5]\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def append(lst, value):\n",
" lst.append(value)\n",
"\n",
"x = [1, 2, 3, 4]\n",
"append(x, 5)\n",
"print x"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"[1, 2, 3, 4, 5]\n"
]
}
],
"prompt_number": 2
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = [1, 2, 3, 4]\n",
"y = list(x) # make a copy x\n",
"x.append(5)\n",
"print x, y"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"[1, 2, 3, 4, 5] [1, 2, 3, 4]\n"
]
}
],
"prompt_number": 3
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = [1, 2, 3, 4]\n",
"y = [1, 2, 3, 4]\n",
"z = x\n",
"print x == y, x is y\n",
"print x == z, x is z"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"True False\n",
"True True\n"
]
}
],
"prompt_number": 4
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print id(x), id(y), id(z)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"4334368096 4334367808 4334368096\n"
]
}
],
"prompt_number": 5
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**The range function**"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"range(10)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 6,
"text": [
"[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]"
]
}
],
"prompt_number": 6
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"range(3, 10)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 8,
"text": [
"[3, 4, 5, 6, 7, 8, 9]"
]
}
],
"prompt_number": 8
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"sum([1, 2, 3, 4])"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 9,
"text": [
"10"
]
}
],
"prompt_number": 9
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"How do you find sum of first 10 integers?"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"sum(range(1, 11))"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 10,
"text": [
"55"
]
}
],
"prompt_number": 10
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem:** Write a function `sum_of_integers` that takes a number n and computes sum of integers from 1..n.\n",
"\n",
" >>> sum_of_integers(10)\n",
" 55"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Write a function `sum_of_squares` that takes a number and computes sum of squares of integers from 1..n.\n",
"\n",
" >>> sum_of_squares(3)\n",
" 14\n",
" >>> sum_of_squares(4)\n",
" 30"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem:** Write a funtion `sigma`, that takes function `f`, `begin` and `end` and computes sum of f applied to `begin`..`end`.\n",
"\n",
" >>> def square(x):\n",
" ... return x*x\n",
" ...\n",
" >>> sigma(square, 1, 4)\n",
" 30"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def sigma(f, begin, end):\n",
" numbers = range(begin, end+1)\n",
" \n",
" values = []\n",
" for n in numbers:\n",
" values.append(f(n))\n",
" \n",
" return sum(values)\n",
"\n",
"def square(x):\n",
" return x * x\n",
"print sigma(square, 1, 4)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"30\n"
]
}
],
"prompt_number": 16
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**List Indexing**"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = ['a', 'b', 'c', 'd']"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 14
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x[0]"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 15,
"text": [
"'a'"
]
}
],
"prompt_number": 15
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x[-1]"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 17,
"text": [
"'d'"
]
}
],
"prompt_number": 17
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x[len(x)-1]"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 18,
"text": [
"'d'"
]
}
],
"prompt_number": 18
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x[0] = 'aa'\n",
"print x"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"['aa', 'b', 'c', 'd']\n"
]
}
],
"prompt_number": 19
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"'b' in x"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 20,
"text": [
"True"
]
}
],
"prompt_number": 20
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"'z' in x"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 21,
"text": [
"False"
]
}
],
"prompt_number": 21
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**List Slicing**"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = ['a', 'b', 'c', 'd', 'e', 'f', 'g']"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 22
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x[0:3] # first three elements"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 23,
"text": [
"['a', 'b', 'c']"
]
}
],
"prompt_number": 23
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x[:3]"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 24,
"text": [
"['a', 'b', 'c']"
]
}
],
"prompt_number": 24
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x[3:] # 3 to the end"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 25,
"text": [
"['d', 'e', 'f', 'g']"
]
}
],
"prompt_number": 25
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x[-3:] # last 3 elements"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 26,
"text": [
"['e', 'f', 'g']"
]
}
],
"prompt_number": 26
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x[:] # make a copy of the list"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 27,
"text": [
"['a', 'b', 'c', 'd', 'e', 'f', 'g']"
]
}
],
"prompt_number": 27
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Write a program `sum.py` that takes multiple numbers as command line arguments and prints their sum.\n",
"\n",
"<pre>\n",
"$ python sum.py 1 2 3 4\n",
"10\n",
"$ python sum.py 1 2 3 4 5 6 7 8 9 10\n",
"55\n",
"</pre>"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Slicing has optional third field."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 29,
"text": [
"['a', 'b', 'c', 'd', 'e', 'f', 'g']"
]
}
],
"prompt_number": 29
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x[0:6:2]"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 31,
"text": [
"['a', 'c', 'e']"
]
}
],
"prompt_number": 31
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x[::2]"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 32,
"text": [
"['a', 'c', 'e', 'g']"
]
}
],
"prompt_number": 32
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x[::-1]"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 33,
"text": [
"['g', 'f', 'e', 'd', 'c', 'b', 'a']"
]
}
],
"prompt_number": 33
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"len(x)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 34,
"text": [
"7"
]
}
],
"prompt_number": 34
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Sorting Lists**"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = [2, 10, 4, 3, 7]\n",
"x.sort() # sorts list in-place\n",
"print x"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"[2, 3, 4, 7, 10]\n"
]
}
],
"prompt_number": 35
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = [2, 10, 4, 3, 7]\n",
"y = sorted(x) # returns a new sorted list\n",
"print y"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"[2, 3, 4, 7, 10]\n"
]
}
],
"prompt_number": 37
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = [2, 4, -5, 7, -8, 9]\n",
"print sorted(x)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"[-8, -5, 2, 4, 7, 9]\n"
]
}
],
"prompt_number": 40
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"How can we sort this list on absolute value of the numbers instead?"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print sorted(x, key=abs)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"[2, 4, -5, 7, -8, 9]\n"
]
}
],
"prompt_number": 41
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Example:** Sorting names by length."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"names = [\"C\", \"Java\", \"Haskell\", \n",
" \"Ruby\", \"Python\"]"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 43
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"sorted(names)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 44,
"text": [
"['C', 'Haskell', 'Java', 'Python', 'Ruby']"
]
}
],
"prompt_number": 44
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"sorted(names, key=len)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 45,
"text": [
"['C', 'Java', 'Ruby', 'Python', 'Haskell']"
]
}
],
"prompt_number": 45
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem:** Write a function `isorted` that takes a list of strings and returns a new list with the names sorted ignoring the case.\n",
"\n",
" >>> isorted([\"Python\", \"C\", \"java\", \"ruby\"])\n",
" [\"C\", \"java\", \"Python\", \"ruby\"]"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Tuples"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = (1, 2, 3)"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 46
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"len(x)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 47,
"text": [
"3"
]
}
],
"prompt_number": 47
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x[0]"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 48,
"text": [
"1"
]
}
],
"prompt_number": 48
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = 1, 2, 3"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 49
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 50,
"text": [
"(1, 2, 3)"
]
}
],
"prompt_number": 50
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def minmax(a, b):\n",
" return min(a, b), max(a, b)"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 51
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x, y = minmax(5, 2)\n",
"print x, y"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"2 5\n"
]
}
],
"prompt_number": 52
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print minmax(5, 2)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"(2, 5)\n"
]
}
],
"prompt_number": 53
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = (1, 2)"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 54
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"y = (1+2)*3"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 55
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"z = (1,)"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 56
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Sets"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = set([1, 5, 3, 4, 2])"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 57
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"print x"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"set([1, 2, 3, 4, 5])\n"
]
}
],
"prompt_number": 58
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"4 in x"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 59,
"text": [
"True"
]
}
],
"prompt_number": 59
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x.add(5)"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 60
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 61,
"text": [
"{1, 2, 3, 4, 5}"
]
}
],
"prompt_number": 61
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Strings"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x = \"hello\"\n",
"y = 'world'"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 62
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"z = \"\"\"First line\n",
"Second line\n",
"Third line\n",
"Line with \"quotes\" in them.\n",
"\"\"\"\n",
"\n",
"print z"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"First line\n",
"Second line\n",
"Third line\n",
"Line with \"quotes\" in them.\n",
"\n"
]
}
],
"prompt_number": 63
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 64,
"text": [
"'hello'"
]
}
],
"prompt_number": 64
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"len(x)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 65,
"text": [
"5"
]
}
],
"prompt_number": 65
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x[0]"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 66,
"text": [
"'h'"
]
}
],
"prompt_number": 66
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"x[:4]"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 67,
"text": [
"'hell'"
]
}
],
"prompt_number": 67
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\"hello world\".split()"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 68,
"text": [
"['hello', 'world']"
]
}
],
"prompt_number": 68
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\"a-b-c-d\".split(\"-\")"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 69,
"text": [
"['a', 'b', 'c', 'd']"
]
}
],
"prompt_number": 69
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Write a function `count_words`, that takes a string and return the number of words in it.\n",
"\n",
" >>> count_words(\"hello world\")\n",
" 2\n",
" >>> count_words(\"python practice book\")\n",
" 3\n",
" \n",
" "
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem** Write a function `getext` to find the extension of given filename.\n",
"\n",
" >>> getext(\"a.py\")\n",
" 'py'\n",
" >>> getext(\"a.c\")\n",
" 'c'\n",
" >>> getext(\"a.tar.gz\")\n",
" 'gz'"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Joining Strings**"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\"-\".join([\"a\", \"b\", \"c\"])"
],
"language": "python",
"metadata": {},
"outputs": [
{
"metadata": {},
"output_type": "pyout",
"prompt_number": 70,
"text": [
"'a-b-c'"
]
}
],
"prompt_number": 70
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem:** Write a function `pathjoin` that takes a list of path names and joins them into single path.\n",
"\n",
" >>> pathjoin([\"foo\", \"bar\", \"a.py\"])\n",
" 'foo/bar/a.py'"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem:** Write a function `extsort` to sort given filenames by extension.\n",
" \n",
" >>> extsort(['a.c', 'a.py', 'b.py', 'bar.txt', 'foo.txt', 'x.c'])\n",
" ['a.c', 'x.c', 'a.py', 'b.py', 'bar.txt', 'foo.txt']\n"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Other useful methods on strings:\n",
"\n",
"* `strip`\n",
"* `replace`\n",
"* `startswith`\n",
"* `endswith`"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"**Problem:** Write a function `plural` to return plural of a word.\n",
"\n",
" >>> plural('word')\n",
" 'words'\n",
" >>> plural('language')\n",
" 'languages'\n",
" >>> plural('try')\n",
" 'tries'\n",
" >>> plural('constituency')\n",
" 'constituencies'\n",
" >>> plural('life')\n",
" 'lives'"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [],
"language": "python",
"metadata": {},
"outputs": []
}
],
"metadata": {}
}
]
}
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