{
 "cells": [
  {
   "cell_type": "markdown",
   "id": "5ec829a7",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "# String formatting"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "130cc097",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "We have talked about strings before, and you know that it is possible to construct strings containing values, e.g."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "51d2701f",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "'x=' + str(43.2) + ', y=' + str(1./3.)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "bf0f4231",
   "metadata": {},
   "source": [
    "However, one may want to format the values in more detail, for example forcing values to be a certain length, or have a certain number of decimal places. This is called *string formatting*."
   ]
  },
  {
   "cell_type": "markdown",
   "id": "8a6a1b0e",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "The syntax for formatting strings looks like this:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "462c1d03",
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "-"
    }
   },
   "outputs": [],
   "source": [
    "\"{0} {1} {2}\".format(1./3., 2./7., 2.)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "e2522672",
   "metadata": {
    "slideshow": {
     "slide_type": "-"
    }
   },
   "source": [
    "In the above example, the ``0``, ``1``, and ``2`` refer to the position of the argument in the parentheses, so one could also do:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "131d89ab",
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "-"
    }
   },
   "outputs": [],
   "source": [
    "\"The quantity {0} that could also be called {0} {1}\".format(1./3., 2./7.)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "8b98fc21",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "By default, the value looks the same as if one had used ``str()``, but you can also specify the format and number of decimal places:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "c417f3b5",
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "-"
    }
   },
   "outputs": [],
   "source": [
    "\"{0:10.3f}\".format(1./3.)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "c5257ae2",
   "metadata": {},
   "source": [
    "The ``f`` stands for floating-point, the 10 is the total length of the string, and the 3 is the nuber of decimal places."
   ]
  },
  {
   "cell_type": "markdown",
   "id": "a9fe4cd2",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "We can do something similar for integers (without the number of decimal places):"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "3c7f537f",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "\"{0:10d}\".format(4)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "787175da",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "There are a number of options for string formatting - for instance, one can add leading zeros:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "14c4d480",
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [],
   "source": [
    "\"{0:010d}\".format(4)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "f3895f73",
   "metadata": {
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "source": [
    "or align to the left:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "63d1da2d",
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [],
   "source": [
    "\"{0:<10d}\".format(4)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "c0ca021a",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "Instead of using ``0``, ``1``, etc. it is also possible to pass the values by name:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "8867ffb4",
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [],
   "source": [
    "\"{day:02d}\".format(day=3)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "84803075",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "Here is an example of string formatting for a date:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "dcf4ee9c",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "\"{year:04d}{month:02d}{day:02d}\".format(year=2013, month=7, day=8)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "99bf270d",
   "metadata": {},
   "source": [
    "## Exercise 1"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "c05ba888",
   "metadata": {},
   "source": [
    "Write a function that takes year, month, day, hour, minutes, and seconds and converts them to a string with format ``2006-03-22 13:12:55``:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "67999f6a",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "# your solution here"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "1a7cfc85",
   "metadata": {},
   "source": [
    "## Exercise 2"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "c80325a6",
   "metadata": {},
   "source": [
    "Write a function that takes a string like ``2006-03-22 13:12:55`` and return the year, month, day, hour, minutes, and seconds as integers:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "77fc6ff6",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "# your solution here"
   ]
  }
 ],
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 "nbformat": 4,
 "nbformat_minor": 5
}