05 - Functions.ipynb

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    "# Functions"
   ]
  },
  {
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   "source": [
    "## [Built-in functions](https://docs.python.org/3/library/functions.html)"
   ]
  },
  {
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   "metadata": {},
   "source": [
    "## Writing functions"
   ]
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   "source": [
    "*Notes: `print` and `return` are completely different things!*"
   ]
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    "All functions return."
   ]
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    "## Keyword arguments"
   ]
  },
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    "Default values"
   ]
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    "Calling functions with keyword arguments"
   ]
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    "## Higher order functions"
   ]
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   "source": [
    "Python supports higher-order functions - passing functions around as first class objects\n",
    "\n",
    "functions can accept other functions as input arguments and return functions to the caller"
   ]
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    "`sorted`\n",
    "\n",
    "has a key parameter to specify a function (or other callable) to be called on each list element prior to making comparisons.\n",
    "\n",
    "https://docs.python.org/3/howto/sorting.html \n",
    "\n",
    "use the key parameter to apply a function to each element of a list as it is being sorted"
   ]
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   "source": [
    "# Scope\n",
    "\n",
    "The LEGB rule: local -> enclosed -> global -> built-in."
   ]
  },
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    "*Note: lower scopes can't modify higher scopes.*"
   ]
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    "a namespace contains all the names available to a particular scope\n",
    "\n",
    "this is a data structure that maps names to objects\n",
    "\n",
    "`dir()` shows the names in the working namespace\n",
    "\n",
    "names that belong to a module can be displayed with: `<module>.__dict__.keys()`"
   ]
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   "source": [
    "## `assert`"
   ]
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   "source": [
    "def add(x, y):\n",
    "    return x + y\n",
    "\n",
    "assert add(1, 2) == 3\n",
    "assert add(-10, 10) == 0"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## *Exercise*\n",
    "\n",
    "__copied from 10x.org.il__\n",
    "\n",
    "Create a function that checks if a string is a valid IPv4 address: composed from 4 numbers between 0 and 255, separated by a dot. Hint: use the `split` and `isdigit` string methods."
   ]
  },
  {
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   "source": [
    "def is_ipv4(address):\n",
    "    # --- WRITE YOUR CODE HERE --- #\n",
    "    \n",
    "    # ---------------------------- #\n",
    "    \n",
    "\n",
    "assert not is_ipv4('')\n",
    "assert not is_ipv4('a')\n",
    "assert not is_ipv4('a.a.a.a')\n",
    "assert not is_ipv4('...')\n",
    "assert not is_ipv4('1.1.9.e')\n",
    "assert not is_ipv4('1.1.1.300')\n",
    "assert not is_ipv4('1.1.1.-1')\n",
    "assert is_ipv4('1.1.1.1')\n",
    "assert is_ipv4('168.0.0.1')"
   ]
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## *Exercise*\n",
    "\n",
    "__copied from 10x.org.il__\n",
    "\n",
    "Write a function that profile (measure the performance) of functions by executing them `times` times and report min, max, and average execution times."
   ]
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    "import time\n",
    "\n",
    "def profile(f, times=100):\n",
    "    \"\"\"\n",
    "    executes `f` `times` times and returns a dictionary with the following info:\n",
    "      * 'min': length of quickest run in seconds\n",
    "      * 'max': length of slowest run in seconds\n",
    "      * 'avg': average time it took to run f\n",
    "     \"\"\"\n",
    "    # --- WRITE YOUR CODE HERE --- #\n",
    "    \n",
    "    # ---------------------------- #\n",
    "\n",
    "\n",
    "def my_function():\n",
    "    time.sleep(random.random() * 0.01)\n",
    "\n",
    "\n",
    "print(profile(my_function))"
   ]
  }
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