01.06 deep vs. shallow copy.ipynb

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    "<h1>Deep vs. shallow copy<span class=\"tocSkip\"></span></h1>\n",
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    "\n",
    "In _Python_, simply copying a variable via `a=b` won’t create a “**deep**“ copy, but just a “**shallow**“ **copy**:"
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    "A = [4, 12, 24]\n",
    "B = A # shallow copy\n",
    "print(\">>>\")\n",
    "print(f\"A and B before changing B (only): {(A,B)}\")"
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    "B[1] = -7\n",
    "print(\">>>\")\n",
    "print(f\"A and B after changing B (ony): {(A,B)}\")"
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    "**deep vs. shallow copy**:\n",
    "* A shallow copy constructs a new compound object and then (to the extent possible) **inserts references** into it to the objects found in the original.\n",
    "* A deep copy constructs a new compound object and then, recursively, **inserts copies** into it of the objects found in the original.\n",
    "\n",
    "The difference between shallow and deep copying is only relevant for compound objects (objects that contain other objects, like lists or class instances)\n",
    "\n",
    "To perform a deep-copy use the `deepcopy`-command the copy-module:"
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    "from copy import deepcopy\n",
    "C=deepcopy(B)\n",
    "print(\">>>\")\n",
    "print(f\"B and C before changing B (only): {(B,C)}\")\n",
    "\n",
    "B[1] = 898\n",
    "print(\">>>\")\n",
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    "Defining a new variable by copying only a subset of a predifined variable also performs a deep-copy:"
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    "D=B[0:2]\n",
    "print(\">>>\")\n",
    "print(f\"D and B before changing B (only): {(D,B)}\")\n",
    "\n",
    "B[0] = 99\n",
    "print(\">>>\")\n",
    "print(f\"D and B after changing B (only): {(D,B)}\")"
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    "E = B+A # <-- no shallow copy problems"
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