tutorials/GitHub_MD_rendering/conditional else vs. completion else.ipynb

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   "source": [
    "# Introduction\n",
    "<hr style = \"border:2px solid black\" ></hr>"
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   "source": [
    "\n",
    "**What?** Conditional else and completion else\n",
    "    \n",
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   "metadata": {},
   "source": [
    "# Conditional else\n",
    "<hr style = \"border:2px solid black\" ></hr>"
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   "source": [
    "\n",
    "- It is **either** the code under the `if` clause that is executed, **or** the code under the `else` block, but not both.  \n",
    "- If the condition of the `if` clause evaluates to `True`, the `if`-block is exectured, and if it evaluated to `False`, it is the `else` block.  \n",
    "\n",
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     "text": [
      "Hello, World!\n"
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   "source": [
    "# conditional else\n",
    "a_list = [1,2]\n",
    "if a_list[0] == 1:\n",
    "    print('Hello, World!')\n",
    "else:\n",
    "    print('Bye, World!')"
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    "# conditional else\n",
    "a_list = [1,2]\n",
    "if a_list[0] == 2:\n",
    "    print('Hello, World!')\n",
    "else:\n",
    "    print('Bye, World!')"
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   "source": [
    "# Completion else\n",
    "<hr style = \"border:2px solid black\" ></hr>"
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    "\n",
    "- **In contrast** to the **either...or*** situation that we know from the conditional `else`, the completion `else` is executed if a code block id finished.  \n",
    "- In the code above, we can see that the code under the **`else`-clause is only executed if the `try-block` was executed without encountering an error, i.e., if the `try`-block is \"complete\".**  \n",
    "- The same rule applies to the \"completion\" `else` in `while`- and `for`-loops, which you can confirm in the following samples below.\n",
    "    \n",
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   "source": [
    "## `try-except`"
   ]
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     "text": [
      "first element: 1\n",
      "no error in try-block\n"
     ]
    }
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   "source": [
    "a_list = [1,2]\n",
    "\n",
    "try:\n",
    "    print('first element:', a_list[0])\n",
    "except IndexError:\n",
    "    print('raised IndexError')\n",
    "else:\n",
    "    print('no error in try-block')"
   ]
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      "raised IndexError\n"
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    "try:\n",
    "    print('third element:', a_list[2])\n",
    "except IndexError:\n",
    "    print('raised IndexError')\n",
    "else:\n",
    "    print('no error in try-block')"
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   "source": [
    "## `while-loop`"
   ]
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     "text": [
      "0\n",
      "1\n",
      "in else\n"
     ]
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   ],
   "source": [
    "i = 0\n",
    "while i < 2:\n",
    "    print(i)\n",
    "    i += 1\n",
    "else:\n",
    "    print('in else')"
   ]
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      "0\n"
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    "i = 0\n",
    "while i < 2:\n",
    "    print(i)\n",
    "    i += 1\n",
    "    break\n",
    "else:\n",
    "    print('completed while-loop')"
   ]
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   "source": [
    "## `for-loop`"
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     "text": [
      "0\n",
      "1\n",
      "completed for-loop\n"
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   "source": [
    "for i in range(2):\n",
    "    print(i)\n",
    "else:\n",
    "    print('completed for-loop')"
   ]
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      "0\n"
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   "source": [
    "for i in range(2):\n",
    "    print(i)\n",
    "    break\n",
    "else:\n",
    "    print('completed for-loop')"
   ]
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   "source": [
    "# References\n",
    "<hr style = \"border:2px solid black\" ></hr>"
   ]
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   "source": [
    "\n",
    "- https://nbviewer.org/github/rasbt/python_reference/blob/master/tutorials/not_so_obvious_python_stuff.ipynb?create=1\n",
    "\n",
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