Moved the exercises for lecture 6 into the lecture notes.

Author: Christian Jacobs

notebook/Lecture-6-Introduction-to-programming-for-geoscientists.ipynb

@@ -8,11 +8,11 @@
   {
    "cells": [
     {
-     "cell_type": "heading",
-     "level": 1,
+     "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "Introduction to programming for Geoscientists (through Python)"
+      "#Introduction to programming for Geoscientists (through Python)\n",
+      "###[Gerard Gorman](http://www.imperial.ac.uk/people/g.gorman), [Christian Jacobs](http://www.imperial.ac.uk/people/c.jacobs10)"
      ]
     },
     {
@@ -21,9 +21,9 @@
      "source": [
       "#Lecture 6: Introduction to classes\n",
       "\n",
-      "[Gerard J. Gorman](http://www.imperial.ac.uk/people/g.gorman) <g.gorman@imperial.ac.uk>\n",
+      "Learning objectives: \n",
       "\n",
-      "Learning objectives: You will learn how to create your own **objects** in Python and develop **member functions** for these new data types."
+      "* Learn how to create your own **objects** in Python and develop **member functions** for these new data types."
      ]
     },
     {
@@ -48,9 +48,9 @@
      ]
     },
     {
-     "cell_type": "raw",
-     "metadata": {},
-     "source": [
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
       "def y(t, v0):\n",
       "    g = 9.81\n",
       "    return v0*t - 0.5*g*t**2\n",
@@ -60,7 +60,10 @@
       "def y(t):\n",
       "    g = 9.81\n",
       "    return v0*t - 0.5*g*t**2"
-     ]
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
     },
     {
      "cell_type": "markdown",
@@ -298,6 +301,89 @@
      ],
      "prompt_number": 4
     },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "## <span style=\"color:blue\">Exercise 1: Make a function class</span>\n",
+      "Make a class called *F* that implements the function\n",
+      "\n",
+      "$$f(x; a, w) = \\exp(\u2212ax)\\sin(wx).$$\n",
+      "\n",
+      "A *value(x)* method computes values of *f*, while *a* and *w* are class attributes.\n"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Test the class with the following main program:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "from math import *\n",
+      "f = F(a=1.0, w=0.1)\n",
+      "print f.value(x=pi)\n",
+      "f.a = 2\n",
+      "print f.value(pi)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "## <span style=\"color:blue\">Exercise 2: Make a very simple class</span>\n",
+      "Make a class called *Simple* with one attribute *i*, one method *double* which replaces the value of *i* by *i+i*, and a constructor that initializes the attribute. "
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Try out the following code for testing the class (but before you run this code, convince yourself what the output of the *print* statements will be):"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "s1 = Simple(4)\n",
+      "for i in range(4):\n",
+      "    s1.double()\n",
+      "print s1.i\n",
+      "\n",
+      "s2 = Simple('Hello')\n",
+      "s2.double(); s2.double()\n",
+      "print s2.i\n",
+      "s2.i = 100\n",
+      "print s2.i"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
     {
      "cell_type": "markdown",
      "metadata": {},
@@ -410,7 +496,23 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "### Protecting attributes\n",
+      "## <span style=\"color:blue\">Exercise 3: Extend a class</span>\n",
+      "Add an attribute called *transactions* to the *Account* class given above. The new attribute counts the number of transactions done in the *deposit* and *withdraw* methods. The total number of transactions should be printed in the *dump* method. Write a simple test program to demonstrate that transaction gets the right value after some calls to *deposit* and *withdraw*."
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "## Protecting attributes\n",
       "It is not possible in Python to explicitly protect attributes from being overwritten by the calling function, *i.e.* the following is possible but not intended:"
      ]
     },
@@ -663,7 +765,65 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "###Special methods for nice syntax\n",
+      "## <span style=\"color:blue\">Exercise 4: Make a class for straight lines</span>\n",
+      "Make a class called *Line* whose constructor takes two points $p_1$ and $p_2$ (2-tuples or 2-lists) as input. The line goes through these two points (see function *line* defined below for the relevant formula of the line). A *value(x)* method computes a value on the line at the point *x*."
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "def line(x0, y0, x1, y1):\n",
+      "    \"\"\"\n",
+      "    Compute the coefficients a and b in the mathematical\n",
+      "    expression for a straight line y = a*x + b that goes\n",
+      "    through two points (x0, y0) and (x1, y1).\n",
+      "    x0, y0: a point on the line (floats).\n",
+      "    x1, y1: another point on the line (floats).\n",
+      "    return: coefficients a, b (floats) for the line (y=a*x+b).\n",
+      "    \"\"\"\n",
+      "    a = (y1 - y0)/float(x1 - x0)\n",
+      "    b = y0 - a*x0\n",
+      "    return a, b"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "## <span style=\"color:blue\">Exercise 5: Make a class for quadratic functions</span>\n",
+      "Consider a quadratic function $f(x; a, b, c) = ax^2 + bx + c$. Make a class called *Quadratic* for representing *f*, where *a*, *b*, and *c* are attributes, and the methods are:\n",
+      "\n",
+      "1. *value* for computing a value of *f* at a point *x*,\n",
+      "2. *table* for writing out a table of *x* and *f* values for n *x* values in the\n",
+      "interval *[L, R]*,\n",
+      "3. *roots* for computing the two roots."
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "##Special methods for nice syntax\n",
       "Some class methods have leading and trailing double underscores, *e.g.*,"
      ]
     },
@@ -861,6 +1021,44 @@
       "a > b                #  a.__gt__(b)\n",
       "a >= b               #  a.__ge__(b)"
      ]
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "## <span style=\"color:blue\">Exercise 6: A very simple \"Hello, World!\" class</span>\n",
+      "Make a class that can only do one thing: *print a* writes \"Hello, World!\" to the screen, where *a* is an instance of the class."
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "## <span style=\"color:blue\">Exercise 7: Use special methods</span>\n",
+      "Modify the class from the first exercise such that the following code works:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "f = F2(1.0, 0.1)\n",
+      "print f(pi)\n",
+      "f.a = 2\n",
+      "print f(pi)\n",
+      "print f"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
     }
    ],
    "metadata": {}