python-primer/episodes/For loops.ipynb

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   "source": [
    "# For loops"
   ]
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   "cell_type": "markdown",
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   "source": [
    "A for loop can be used to repeat actions over a set of values."
   ]
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     "text": [
      "J\n",
      "i\n",
      "m\n",
      "m\n",
      "y\n"
     ]
    }
   ],
   "source": [
    "name = 'Jimmy'\n",
    "\n",
    "for letter in name:\n",
    "    print(letter)"
   ]
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   "metadata": {},
   "source": [
    "For loops are constructed via the syntax for LOOP_VARIABLE in ITERABLE.  The loop variable in the above example I've used is `letter` and the iterable I've used is the string `name`, which was defined as `'Jimmy'`.  Other iterables include lists and dictionary keys, which we'll discuss later.  You can construct an iterable corresponding to a set of numbers beginning at 0 and ending at a certain number by using the built-in range function:"
   ]
  },
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   "cell_type": "code",
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   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0\n",
      "1\n",
      "2\n",
      "3\n",
      "4\n",
      "5\n"
     ]
    }
   ],
   "source": [
    "for number in range(6):\n",
    "    print(number)"
   ]
  },
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   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
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     "text": [
      "2 is even\n",
      "4 is even\n",
      "6 is even\n",
      "8 is even\n"
     ]
    }
   ],
   "source": [
    "for number in range(2, 10):\n",
    "    if number % 2 == 0:\n",
    "        print(number, \"is even\")"
   ]
  },
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   "cell_type": "code",
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   "metadata": {},
   "outputs": [
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     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Sum of numbers from 0 to 5 is 15\n"
     ]
    }
   ],
   "source": [
    "my_sum = 0\n",
    "\n",
    "for number in range(6):\n",
    "    my_sum += number\n",
    "print(\"Sum of numbers from 0 to 5 is\", my_sum)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Letter 0 - J\n",
      "Letter 1 - i\n",
      "Letter 2 - m\n",
      "Letter 3 - m\n",
      "Letter 4 - y\n"
     ]
    }
   ],
   "source": [
    "for n, letter in enumerate(name):\n",
    "    print(\"Letter\", n, \"-\", letter)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Iterables have a length, and you can find this length using the len function."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Length of Jimmy is 5\n"
     ]
    }
   ],
   "source": [
    "print(\"Length of\", name, \"is\", len(name))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "J H\n",
      "i e\n",
      "m a\n",
      "m t\n",
      "y h\n"
     ]
    }
   ],
   "source": [
    "for letter1, letter2 in zip(\"Jimmy\", \"Heath\"):\n",
    "    print(letter1, letter2)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Exercise: write a for loop that computes the sum of all of the squares from 2 to 11."
   ]
  }
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