Lessons/Functions.ipynb

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    "# Functions"
   ]
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   "source": [
    "A **function is a block of organised, reusable code that is used to carry out a single, related action**. Functions provide better modularity for your application and a high degree of code reusing. They can also let us specify parameters that can serve as inputs to the functions. The concept of function will also allow us to start thinking of program design. Defining part a function in Python is done using the ```def``` keyword:\n",
    "\n",
    "```python\n",
    "def name_of_function(arg1,arg2): # arg1, arg2 are optional arguments\n",
    "    '''\n",
    "    This is where the functionyou desceibe what is this function for\n",
    "    '''\n",
    "    # Coding what you want your function to do\n",
    "    \n",
    "    return desired result # This is opptional \n",
    "```    "
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   "source": [
    "# Function that greets people with their name.\n",
    "def greetings(name):\n",
    "    print 'Hello {0}'.format(name)"
   ]
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   "source": [
    "greetings(\"Tom\")"
   ]
  },
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   "source": [
    "**return** allows a function to return a result that can then be stored as a variable, or used in whatever manner we want."
   ]
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   "source": [
    "# Example of fucntion adding two numbers\n",
    "def add_numbers(a, b):\n",
    "    return a + b"
   ]
  },
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   "source": [
    "add_numbers(3, 4)"
   ]
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   "source": [
    "# Can also save as variable due to return\n",
    "result = add_numbers(3, 4)"
   ]
  },
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   "source": [
    "print result"
   ]
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   "source": [
    "#  if we input two strings\n",
    "print add_numbers('one','two')"
   ]
  },
  {
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   "source": [
    "Now we will modify the function to take a third argument."
   ]
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   "source": [
    "def add_numbers(a, b, c=None):\n",
    "    if c == None:\n",
    "        return a + b\n",
    "    else:\n",
    "        return a + b + c"
   ]
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   "source": [
    "print(add_numbers(3,4))\n",
    "print(add_numbers(3,4,5))"
   ]
  },
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   "cell_type": "markdown",
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   "source": [
    "Updated to take an optional flag parameter."
   ]
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   "source": [
    "def add_numbers(a, b, c=None, flag=False):\n",
    "    if flag:\n",
    "        print \"Flag is true\"\n",
    "    if c == None:\n",
    "        return a + b\n",
    "    else:\n",
    "        return a + b + c"
   ]
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   "outputs": [],
   "source": [
    "print(add_numbers(3,4,5))\n",
    "print(add_numbers(3,4,5,flag=True))"
   ]
  },
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   "source": [
    "Assign function add_numbers to variable *a*."
   ]
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   "source": [
    "a = add_numbers"
   ]
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   "source": [
    "a(3,5)"
   ]
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   "source": [
    "Let's calculate the area of a circle."
   ]
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   "source": [
    "def area_circle(radius):\n",
    "    pi = 3.1416\n",
    "    'Function that calculates the area of a circle'\n",
    "    area = pi * radius ** 2\n",
    "    print area\n",
    "    #return area\n",
    "\n",
    "# Radious in cm\n",
    "list_radius = [1, 2, 3, 4, 5, 6]\n",
    "\n",
    "for radius in list_radius:\n",
    "    print (area_circle(radius))\n",
    "    #area = area_circle(radius)\n",
    "    #print \"The area of a circle of radius \", radius, \"cm\"\n",
    "    #print \"cm is\", area, \"cm^2\"\n",
    "print \"Finished to calculate the areas of circles\""
   ]
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   "source": [
    "# A quick practice!"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Write a Python function to multiply all the numbers in a list.\n",
    "* Sample List : [1, 2, 3, -4]\n",
    "* Expected Output : -24"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
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   "outputs": [],
   "source": [
    "def multiply(numbers): "
   ]
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   "source": [
    "multiply([1,2,3,-4])"
   ]
  },
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   "metadata": {},
   "source": [
    "Write a Python function that takes a list and returns a new list with unique elements of the first list.\n",
    "* Sample List : [1,1,1,1,2,2,3,3,3,3,4,5]\n",
    "* Unique List : [1, 2, 3, 4, 5]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
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   "outputs": [],
   "source": [
    "def unique_list(l):"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
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   "outputs": [],
   "source": [
    "unique_list([1,1,1,1,2,2,3,3,3,3,4,5])\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Write a Python function that accepts a string and calculate the number of upper case letters and lower case letters.\n",
    "* Sample String : 'Hello Mr. Rogers, how are you this fine Tuesday?'\n",
    "* Expected Output : \n",
    "  * No. of Upper case characters : 4\n",
    "  * No. of Lower case Characters : 33"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
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   "outputs": [],
   "source": [
    "def up_low(s):"
   ]
  }
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