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immutable tuple upd.

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rasbt 2014-04-15 21:04:35 -04:00
parent 80cb86a801
commit 945885ffba
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38
.ipynb_checkpoints/not_so_obvious_python_stuff-checkpoint.ipynb
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@ -1,7 +1,7 @@
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@ -48,7 +48,7 @@
"- [`bool` is a subclass of `int`](#bool_int)\n",
"- [About lambda and closures-in-a-loop pitfall](#lambda_closure)\n",
"- [Python's LEGB scope resolution and the keywords `global` and `nonlocal`](#python_legb)\n",
"- [When immutable Tuples aren't so immutable](#immutable_tuple)\n",
"- [When mutable contents of immutable tuples aren't so mutable](#immutable_tuple)\n",
"- [List comprehensions are fast, but generators are faster!?](#list_generator)"
]
},
@ -830,17 +830,16 @@
"<br>\n",
"<br>\n",
"<a name='immutable_tuple'></a>\n",
"## When immutable Tuples aren't so immutable"
"## When mutable contents of immutable tuples aren't so mutable"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"As we all know, tuples are immutable objects in Python, right!?\n",
"As we all know, tuples are immutable objects in Python, right!? But what happens if they contain mutable objects? \n",
"\n",
"**Note:** As a careful reader pointed out, \n",
"\"The tuple is still immutable. You were unable to change it's cardinality, or trick it into pointing to a different contained object.\""
"First, let us have a look at the expected behavior: a `TypeError` is raised if we try to modify a value tuple: "
]
},
{
@ -870,7 +869,7 @@
"cell_type": "markdown",
"metadata": {},
"source": [
"#### But what if we put a mutable object into the immutable tuple? Well, modification works, but we **also** get a type error, funny, isn't it?"
"#### But what if we put a mutable object into the immutable tuple? Well, modification works, but we **also** get a `TypeError` at the same time."
]
},
{
@ -929,7 +928,7 @@
"source": [
"<br>\n",
"<br>\n",
"However, there **IS** a way (where there should be none!) to modify our immutable tuple without raising the `TypeError`, the solution is the `.extend()`:"
"However, **there are ways** to modify the mutable contents of the tuple without raising the `TypeError`, the solution is the `.extend()` method, or alternatively `.append()` (for lists):"
]
},
{
@ -955,6 +954,29 @@
],
"prompt_number": 44
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{
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"collapsed": false,
"input": [
"tup = ([],)\n",
"print('tup before: ', tup)\n",
"tup[0].append(1)\n",
"print('tup after: ', tup)"
],
"language": "python",
"metadata": {},
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{
"output_type": "stream",
"stream": "stdout",
"text": [
"tup before: ([],)\n",
"tup after: ([1],)\n"
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38
not_so_obvious_python_stuff.ipynb
View File

@ -1,7 +1,7 @@
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@ -48,7 +48,7 @@
"- [`bool` is a subclass of `int`](#bool_int)\n",
"- [About lambda and closures-in-a-loop pitfall](#lambda_closure)\n",
"- [Python's LEGB scope resolution and the keywords `global` and `nonlocal`](#python_legb)\n",
"- [When immutable Tuples aren't so immutable](#immutable_tuple)\n",
"- [When mutable contents of immutable tuples aren't so mutable](#immutable_tuple)\n",
"- [List comprehensions are fast, but generators are faster!?](#list_generator)"
]
},
@ -830,17 +830,16 @@
"<br>\n",
"<br>\n",
"<a name='immutable_tuple'></a>\n",
"## When immutable Tuples aren't so immutable"
"## When mutable contents of immutable tuples aren't so mutable"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"As we all know, tuples are immutable objects in Python, right!?\n",
"As we all know, tuples are immutable objects in Python, right!? But what happens if they contain mutable objects? \n",
"\n",
"**Note:** As a careful reader pointed out, \n",
"\"The tuple is still immutable. You were unable to change it's cardinality, or trick it into pointing to a different contained object.\""
"First, let us have a look at the expected behavior: a `TypeError` is raised if we try to modify a value tuple: "
]
},
{
@ -870,7 +869,7 @@
"cell_type": "markdown",
"metadata": {},
"source": [
"#### But what if we put a mutable object into the immutable tuple? Well, modification works, but we **also** get a type error, funny, isn't it?"
"#### But what if we put a mutable object into the immutable tuple? Well, modification works, but we **also** get a `TypeError` at the same time."
]
},
{
@ -929,7 +928,7 @@
"source": [
"<br>\n",
"<br>\n",
"However, there **IS** a way (where there should be none!) to modify our immutable tuple without raising the `TypeError`, the solution is the `.extend()`:"
"However, **there are ways** to modify the mutable contents of the tuple without raising the `TypeError`, the solution is the `.extend()` method, or alternatively `.append()` (for lists):"
]
},
{
@ -955,6 +954,29 @@
],
"prompt_number": 44
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"tup = ([],)\n",
"print('tup before: ', tup)\n",
"tup[0].append(1)\n",
"print('tup after: ', tup)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"tup before: ([],)\n",
"tup after: ([1],)\n"
]
}
],
"prompt_number": 5
},
{
"cell_type": "markdown",
"metadata": {},