02_Repeating_with_Loops.ipynb

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    "# II. Making Choices\n"
   ]
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   "source": [
    "## Teaching"
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    "## Exercices\n"
   ]
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    "### From 1 to N\n",
    "\n",
    "Python has a built-in function called `range` that generates a sequence of numbers. `range` can accept 1, 2, or 3 parameters.\n",
    "\n",
    "* If one parameter is given, `range` generates a sequence of that length, starting at zero and incrementing by 1. For example, `range(3)` produces the numbers `0, 1, 2`.\n",
    "* If two parameters are given, `range` starts at the first and ends just before the second, incrementing by one. For example, `range(2, 5)` produces `2, 3, 4`.\n",
    "* If `range` is given 3 parameters, it starts at the first one, ends just before the second one, and increments by the third one. For example, `range(3, 10, 2)` produces `3, 5, 7, 9`.\n",
    "\n",
    "Using `range`, write a loop that uses `range` to print the first 3 natural numbers:   \n",
    "    1   \n",
    "    2   \n",
    "    3   "
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    "### Understanding the loops\n",
    "\n",
    "Given the following loop:"
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      "o\n",
      "x\n",
      "y\n",
      "g\n",
      "e\n",
      "n\n"
     ]
    }
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   "source": [
    "word = 'oxygen'\n",
    "for char in word:\n",
    "    print(char)"
   ]
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    "ButHow many times is the body of the loop executed?\n",
    "\n",
    "    3 times\n",
    "    4 times\n",
    "    5 times\n",
    "    6 times\n"
   ]
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    "### Computing Powers With Loops\n",
    "\n",
    "Exponentiation is built into Python:"
   ]
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      "125\n"
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    "print(5 ** 3)"
   ]
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    "Write a loop that calculates the same result as `5 ** 3` using multiplication (and without exponentiation)."
   ]
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    "### Reverse a String\n",
    "\n",
    "Knowing that two strings can be concatenated using the `+` operator, write a loop that takes a string and produces a new string with the characters in reverse order, so `'Newton'` becomes `'notweN'`."
   ]
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    "### Computing the Value of a Polynomial\n",
    "\n",
    "The built-in function `enumerate` takes a sequence (e.g. a list) and generates a new sequence of the same length. Each element of the new sequence is a pair composed of the index (0, 1, 2,…) and the value from the original sequence:\n",
    "\n",
    "```\n",
    "for i, x in enumerate(xs):\n",
    "    # Do something using i and x\n",
    "```\n",
    "\n",
    "The code above loops through `xs`, assigning the index to `i` and the value to `x`.\n",
    "\n",
    "Suppose you have encoded a polynomial as a list of coefficients in the following way: the first element is the constant term, the second element is the coefficient of the linear term, the third is the coefficient of the quadratic term, etc.\n",
    "\n",
    "```\n",
    "x = 5\n",
    "cc = [2, 4, 3]\n",
    "\n",
    "# output\n",
    "y = cc[0] * x**0 + cc[1] * x**1 + cc[2] * x**2\n",
    "y = 97\n",
    "```\n",
    "\n",
    "Write a loop using `enumerate(cc)` which computes the value y of any polynomial, given `x` and `cc`."
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