fstrings.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br>*To run a cell in a Jupyter notebook, click in the gray code cell and press the \"play\" arrow or hold down shift key and press return (or shift+enter).*"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# fstrings"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "In this notebook, we are going to cover how to **build strings out of variables and strings**. This is a very common task in Python."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Some examples:"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**Building filenames**"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "old_filename = \"myfile\"\n",
    "new_filename = old_filename + \"_ver2\"\n",
    "print(new_filename)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**Reporting results**"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "size_list = [5.4, 8.4, 9.2, 4.7, 8.8]\n",
    "print(\"The mean size is \" + str(sum(size_list)/len(size_list)))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**Creating unique identifiers**"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "run_num = \"6\"\n",
    "condition = \"control\"\n",
    "date = \"010420\"\n",
    "ID = run_num + \"_\" + condition + \"_\" + date\n",
    "print(ID)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br><br>Over the years, Python has introduced several methods to make this a shorter process than using the `+` between the strings and variables. Each new method has made the process a little bit shorter."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "One previous method was `format()`:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "old_filename = \"myfile\"\n",
    "version = \"2\"\n",
    "new_filename = \"{}_ver{}\".format(old_filename, version)\n",
    "print(new_filename)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br>In the `format()` method, the arguments that were passed to the `format()` function would get filled into the curly brackets inside the string, in the order that you entered them."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "If you entered the arguments in the wrong order or forgot to provide an argument, you would either get the wrong result or an error:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "new_filename = \"{}_ver{}\".format(version, old_filename)\n",
    "print(new_filename)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "new_filename = \"{}_ver{}\".format(old_filename)\n",
    "print(new_filename)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br><br>The latest solution prevents these common user errors by moving the variable names into the string. These are called **fstrings**."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### <br>fstring syntax"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "new_filename = f\"{old_filename}_ver{version}\"\n",
    "print(new_filename)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br>fstrings begin with the letter `f` followed by the opening quotation mark. <br>You can use either a single or double quotation mark, just like with an ordinary string.\n",
    "<br>Do not put a space between `f` and the first `\"`."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br> Variable names now go inside the the curly brackets inside the string."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The string ends with the closing quotation mark."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br>Here's an example using single quotation marks:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "new_filename = f'{old_filename}_ver{version}'\n",
    "print(new_filename)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br>And here's an example with a space between the `f` and the first `\"`:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "new_filename = f \"{old_filename}_ver{version}\"\n",
    "print(new_filename)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# <br><br>fstring examples and practice exercises"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## <br><br>Example 1"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "name = \"Colby\"\n",
    "adj = \"adventurous\""
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### <br>Old way:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "hb = \"Happy Birthday, \" + name + \"! Have an \" + adj + \" day.\"\n",
    "print(hb)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### <br>fstring:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "hb = f\"Happy Birthday, {name}! Have an {adj} day.\"\n",
    "print(hb)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br><br>*NOTE: If you want to include curly brackets in a string, you can surround them with another set of curly brackets.*"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "hb = f\"Happy Birthday, {{name}}! Have a {adj} day. {{}}\"\n",
    "print(hb)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### <br><br>Exercise 1"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "First run this cell:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "animal = \"ox\"\n",
    "month = \"February\"\n",
    "day = 12\n",
    "year = 2021"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br>Now write an fstring to print: The year of the ox will begin on February 12, 2021."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "sentence = \n",
    "print(sentence)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## <br><br><br><br>Example 2"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Did you notice anything interesting about how numbers were handled in that exercise?"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "count = 3.5"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### <br>Old way"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "print(\"Yesterday I ate \" + count + \" cookies.\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br><br>We would have to explicitly change `count` to a string in order to include it in the string:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "print(\"Yesterday I ate \" + str(count) + \" cookies.\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### <br><br>fstring"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "An fstring automatically changes any integer or float to a string:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "print(f\"Yesterday I ate {count} cookies.\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br><br>Let's see how fstrings handle lists."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "cookies = [\"Oreo\", \"snickerdoodle\", \"oatmeal chocolate chip\"]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "print(f\"The cookies I ate were {cookies}.\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br><br>Instead we can index the items in the list:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "print(f\"The cookies I ate were {cookies[0]}, {cookies[1]}, and {cookies[2]}.\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br><br>Sometimes we don't know how many items will be in a list (and no, `*cookies` doesn't work to unpack a list in an fstring)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Let's review list indexing and the `join()` function."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "cookies = [\"Oreo\", \"snickerdoodle\", \"oatmeal chocolate chip\"]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br>Before running the cells below, take a minute to think - what will these print?"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "cookies[1:]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "cookies[:-1]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br><br>If we don't specify an index after the `:` if will print to the end."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "If we don't specify an index before the `:` if will print from the beginning."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br><br>The `join()` function is handy for creating a string out of a list of unknown length."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "\"\".join(cookies)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "\" \".join(cookies)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "\", \".join(cookies)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br>Combine `join()` with indexing:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "\", \".join(cookies[:-1])"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br><br>Now we can combine that to make a nice, neat sentence:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "print(f\"The cookies I ate were {\", \".join(cookies[:-1])}, and {cookies[-1]}.\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br><br><br>Uh-oh! When referencing a string inside a string, use single quotes `'` inside double quotes `\"`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "print(f\"The cookies I ate were {', '.join(cookies[:-1])}, and {cookies[-1]}.\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### <br><br>Exercise 2"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "name = \"Colby\"\n",
    "grades = [85, 89, 87, 83, 10]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br>Write an fstring to say Dear Colby, Your exam grades were 85, 89, 87, and 83, and your participation grade was 10."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "*Note:* `join()` can't implicitly join integers into a string. You have three options:\n",
    "<br>- Beginner: index the grades individually in your fstring.\n",
    "<br>- Intermediate: Before the `letter` variable assignment, write a for loop to change all the items in `grades` to strings.\n",
    "<br>- Advanced: Use a list comprehension to change the grades to strings inside the `join()` function inside the fstring."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "letter = \n",
    "print(letter)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## <br><br><br>Example 3"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "fstrings aren't only for variables!!"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "f\"Eat {6 + 5} kiwis.\""
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "f\"Eat {2**10 / (13-3)} kiwis.\""
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "kiwi_piles = [10, 9, 13, 7]\n",
    "f\"Eat {sum(kiwi_piles)} kiwis.\""
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "kiwi_dreams = \"one hundred\"\n",
    "f\"Eat {kiwi_dreams.upper()} kiwis.\""
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### <br><br>Exercise 3"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "name = \"Colby\"\n",
    "count = 11"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "I said I ate 11 kiwis, but you saw me eat 3 more kiwis in secret. Change the code below to reflect the truth:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "print(f\"{name} ate {count} kiwis.\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## <br><br>Example 4"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Let's practice using fstrings with dictionaries."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Here is a **list of dictionaries** with info about six experiments:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "results_list = [{\"run\": 1, \"date\": \"013020\", \"condition\": \"control\", \"result\": 1.3849}, \n",
    "                 {\"run\": 1, \"date\": \"013020\", \"condition\": \"cold\", \"result\": .8309},\n",
    "                 {\"run\": 2, \"date\": \"013020\", \"condition\": \"control\", \"result\": 1.1384},\n",
    "                 {\"run\": 2, \"date\": \"013020\", \"condition\": \"cold\", \"result\": 1.0867},\n",
    "                 {\"run\": 3, \"date\": \"013020\", \"condition\": \"control\", \"result\": .8479},\n",
    "                 {\"run\": 3, \"date\": \"013020\", \"condition\": \"cold\", \"result\": .7238}]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br>We want to create a results file for each experiment. (So we need to loop through the list.)<br>To create a unique identifier for each result, we will combine the condition, run number, and the word \"results\", in addition to a file extension."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "for i in results_list:\n",
    "    #remember that each i is a dictionary\n",
    "    new_filename = f\"{i['condition']}_{i['run']}_results.txt\"\n",
    "    print(new_filename)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### <br><br>Exercise 4"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "results_dicts = [{\"run\": 1, \"date\": \"013020\", \"condition\": \"control\", \"result\": 1.3849}, \n",
    "                 {\"run\": 1, \"date\": \"013020\", \"condition\": \"cold\", \"result\": .8309},\n",
    "                 {\"run\": 2, \"date\": \"013020\", \"condition\": \"control\", \"result\": 1.1384},\n",
    "                 {\"run\": 2, \"date\": \"013020\", \"condition\": \"cold\", \"result\": 1.0867},\n",
    "                 {\"run\": 3, \"date\": \"013020\", \"condition\": \"control\", \"result\": .8479},\n",
    "                 {\"run\": 3, \"date\": \"013020\", \"condition\": \"cold\", \"result\": .7238}]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "For each experiment, print a complete sentence with the date, run, condition, and result. Use the `round()` function to round the result to two decimal places."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The sentence for the first experiment should read: On 013020, I conducted a control experiment; the result from run 1 was 1.38."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<br>*Don't forget that you need to use single quotes inside double quotes.*"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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