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keyword unpacking syntax

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rasbt 2014-05-01 02:22:43 -04:00
parent a0edd6b293
commit 6253c112f2
2 changed files with 250 additions and 4 deletions
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127
.ipynb_checkpoints/not_so_obvious_python_stuff-checkpoint.ipynb
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@ -1,7 +1,7 @@
{
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@ -80,7 +80,8 @@
"- [Key differences between Python 2 and 3](#python_differences)\n",
"- [Function annotations - What are those `->`'s in my Python code?](#function_annotation)\n",
"- [Abortive statements in `finally` blocks](#finally_blocks)\n",
"- [Assigning types to variables as values](#variable_types)"
"- [Assigning types to variables as values](#variable_types)\n",
"- [Keyword argument unpacking syntax - `*args` and `**kwargs`](#splat_op)"
]
},
{
@ -2979,6 +2980,125 @@
],
"prompt_number": 4
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<a name=\"splat_op\"></a>\n",
"<br>\n",
"<br>"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"##Keyword argument unpacking syntax - `*args` and `**kwargs`"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Python has a very convenient \"keyword argument unpacking syntax\" (often also referred to as \"splat\"-operators). This is particularly useful, if we want to define a function that can take a arbitrary number of input arguments."
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"#### Single-asterisk (*args)"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def a_func(*args):\n",
" print('type of args:', type(args))\n",
" print('args contents:', args)\n",
" print('1st argument:', args[0])\n",
"\n",
"a_func(0, 1, 'a', 'b', 'c')"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"type of args: <class 'tuple'>\n",
"args contents: (0, 1, 'a', 'b', 'c')\n",
"1st argument: 0\n"
]
}
],
"prompt_number": 30
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"#### Double-asterisk (**kwargs)"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def b_func(**kwargs):\n",
" print('type of kwargs:', type(kwargs))\n",
" print('kwargs contents: ', kwargs)\n",
" print('value of argument a:', kwargs['a'])\n",
" \n",
"b_func(a=1, b=2, c=3, d=4)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"type of kwargs: <class 'dict'>\n",
"kwargs contents: {'d': 4, 'c': 3, 'b': 2, 'a': 1}\n",
"value of argument a: 1\n"
]
}
],
"prompt_number": 35
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"#### (Partially) unpacking of iterables\n",
"Another useful application of the \"unpacking\"-operator is the unpacking of lists and other other iterables."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"val1, *vals = [1, 2, 3, 4, 5]\n",
"print('val1:', val1)\n",
"print('vals:', vals)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"val1: 1\n",
"vals: [2, 3, 4, 5]\n"
]
}
],
"prompt_number": 36
},
{
"cell_type": "markdown",
"metadata": {},
@ -3008,6 +3128,9 @@
"cell_type": "markdown",
"metadata": {},
"source": [
"#### 05/01/2014\n",
"- new section: keyword argument unpacking syntax\n",
"\n",
"#### 04/27/2014\n",
"- minor fixes of typos\n",
"- single- vs. double-underscore clarification in the private class section."

127
not_so_obvious_python_stuff.ipynb
View File

@ -1,7 +1,7 @@
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"signature": "sha256:9a07a78204a51f0faab65e52657f0446cd604ed470627f9c6af1ba74c047fe23"
},
"nbformat": 3,
"nbformat_minor": 0,
@ -80,7 +80,8 @@
"- [Key differences between Python 2 and 3](#python_differences)\n",
"- [Function annotations - What are those `->`'s in my Python code?](#function_annotation)\n",
"- [Abortive statements in `finally` blocks](#finally_blocks)\n",
"- [Assigning types to variables as values](#variable_types)"
"- [Assigning types to variables as values](#variable_types)\n",
"- [Keyword argument unpacking syntax - `*args` and `**kwargs`](#splat_op)"
]
},
{
@ -2979,6 +2980,125 @@
],
"prompt_number": 4
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<a name=\"splat_op\"></a>\n",
"<br>\n",
"<br>"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"##Keyword argument unpacking syntax - `*args` and `**kwargs`"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Python has a very convenient \"keyword argument unpacking syntax\" (often also referred to as \"splat\"-operators). This is particularly useful, if we want to define a function that can take a arbitrary number of input arguments."
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"#### Single-asterisk (*args)"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def a_func(*args):\n",
" print('type of args:', type(args))\n",
" print('args contents:', args)\n",
" print('1st argument:', args[0])\n",
"\n",
"a_func(0, 1, 'a', 'b', 'c')"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"type of args: <class 'tuple'>\n",
"args contents: (0, 1, 'a', 'b', 'c')\n",
"1st argument: 0\n"
]
}
],
"prompt_number": 30
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"#### Double-asterisk (**kwargs)"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"def b_func(**kwargs):\n",
" print('type of kwargs:', type(kwargs))\n",
" print('kwargs contents: ', kwargs)\n",
" print('value of argument a:', kwargs['a'])\n",
" \n",
"b_func(a=1, b=2, c=3, d=4)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"type of kwargs: <class 'dict'>\n",
"kwargs contents: {'d': 4, 'c': 3, 'b': 2, 'a': 1}\n",
"value of argument a: 1\n"
]
}
],
"prompt_number": 35
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"#### (Partially) unpacking of iterables\n",
"Another useful application of the \"unpacking\"-operator is the unpacking of lists and other other iterables."
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"val1, *vals = [1, 2, 3, 4, 5]\n",
"print('val1:', val1)\n",
"print('vals:', vals)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"val1: 1\n",
"vals: [2, 3, 4, 5]\n"
]
}
],
"prompt_number": 36
},
{
"cell_type": "markdown",
"metadata": {},
@ -3008,6 +3128,9 @@
"cell_type": "markdown",
"metadata": {},
"source": [
"#### 05/01/2014\n",
"- new section: keyword argument unpacking syntax\n",
"\n",
"#### 04/27/2014\n",
"- minor fixes of typos\n",
"- single- vs. double-underscore clarification in the private class section."