notes/L2-Folders.ipynb

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 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Directories and Folder structures"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Now that we've started working with files, let's take a moment to learn a little more about how your computer stores your files.\n",
    "So far, we've noticed a few things about files:\n",
    "1. They have a **name** (like `temp` or `numbers`)\n",
    "2. Their name has an **extension** (like `.txt` or `.csv`), which describes the file type\n",
    "3. They usually have some **contents** (like lines of text, or lists of comma-separated values)\n",
    "\n",
    "Files also have a **location** on your computer. \n",
    "- We say that files are stored in a **folder** or **directory**\n",
    "- The location of a file is described by its **filepath**\n",
    "\n",
    "Files are organized in a tree structure. For example, in our class notes directory we have a structure like:\n",
    "\n",
    "    introduction-to-python\n",
    "      |__ data\n",
    "            |__ restaurant-names.txt            \n",
    "            |__ restaurants.txt\n",
    "      |__ notes\n",
    "            |__ A-Introduction_to_iPython_Notebooks.ipynb      \n",
    "            |__ B-Numeric_Expressions.ipynb       \n",
    "            |__ C1-Variables.ipynb             \n",
    "            |__ ...\n",
    "      |__ binder\n",
    "            |__ ...\n",
    "      |__ ...\n",
    "      \n",
    " So, within the directory this notebook would be located at `introduction-to-python/notes/L2-folders.ipynb`."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Working with the os module"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Let's understand this a little better. To do so, we'll import the `os` module, a convenient way to work with files from within Python."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
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   "outputs": [],
   "source": [
    "import os"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Print the current directory and explore it"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Let's use `os.getcwd()` to print the current working directory (`cwd`)."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
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   "outputs": [],
   "source": [
    "# Print the working directory\n",
    "start_directory = os.getcwd()\n",
    "print(f\"We are now in:\\n{start_directory}\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "You should not be surprised to see that you are sitting in the `introduction-to-python/notes/` folder.    \n",
    "What's here? Let's use `os.listdir()` to list the files in the directory."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false,
    "scrolled": true
   },
   "outputs": [],
   "source": [
    "# Let's see what kind of files are in this directory \n",
    "os.listdir()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "# Are there some notebooks about Strings here?\n",
    "[f for f in os.listdir() if 'String' in f]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "# What kinds of .csv or .txt files are there here? I guess none.\n",
    "[f for f in os.listdir() if f.endswith(\".csv\") or f.endswith(\".txt\")]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Creating a new directory"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Let's make a directory for the files we made today using `os.makedirs()`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
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   "outputs": [],
   "source": [
    "# Create our directory\n",
    "new_directory = start_directory + \"/practice_files\"\n",
    "os.makedirs(new_directory)\n",
    "print(f\"We are making a new directory called:\\n{new_directory}\\n\")\n",
    "\n",
    "# Check that it's there\n",
    "print(\"Did we make it?\")\n",
    "print('practice_files' in os.listdir())"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Changing directories"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Let's enter (change to) the directory that we made using `os.chdir()`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "# Move to new directory\n",
    "os.chdir(new_directory)                                # Change the directory\n",
    "print(f\"Ok. We are now in directory:\\n{os.getcwd()}\")  # Confirm that we're there"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
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   "outputs": [],
   "source": [
    "# And, we can go back:\n",
    "os.chdir(start_directory)                              # Change the directory\n",
    "print(f\"Ok. We are now in directory:\\n{os.getcwd()}\")  # Confirm that we're there"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Relative file paths"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "One convenient tool that you can use is **relative file paths**. For example, so far we have used the full filepaths to navigate:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
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    "collapsed": false
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   "outputs": [],
   "source": [
    "print(start_directory)\n",
    "print(new_directory)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "However, we can also move using filepaths that are defined _relative to our current location_. For example, from our position in `01-Introduction_to_Python`:\n",
    "- We can easily move down into a folder on the next level using its name, e.g. `practice_files/`\n",
    "- We can move up one level by using the `../` shorthand"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "# Where are we again? \n",
    "print(f\"Ok. We are now in directory: {os.getcwd()}\")  "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
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   "outputs": [],
   "source": [
    "# Go down\n",
    "os.chdir('practice_files/')                           # Change the directory\n",
    "print(f\"Ok. We are now in directory: {os.getcwd()}\")  # Confirm that we're there"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
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   "outputs": [],
   "source": [
    "# Go up\n",
    "os.chdir('../')                                       # Change the directory\n",
    "print(f\"Ok. We are now in directory: {os.getcwd()}\")  # Confirm that we're there\n",
    "\n",
    "# Go up two steps\n",
    "os.chdir('../../')                                    # Change the directory\n",
    "print(f\"Ok. We are now in directory: {os.getcwd()}\")  # Confirm that we're there"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "# Go down into the SQl folder\n",
    "os.chdir('introduction-to-python/data/')       # Change the directory\n",
    "print(f\"Ok. We are now in directory: {os.getcwd()}\")  # Confirm that we're there\n",
    "\n",
    "# Move up and then down (i.e. move laterally)\n",
    "os.chdir('../notes/')             # Change the directory\n",
    "print(f\"Ok. We are now in directory: {os.getcwd()}\")  # Confirm that we're there"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Moving files"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "We can use `os.rename(old_name, new_name)` to rename files. \n",
    "- Be careful, because this will overwrite any existing files called `new_name`.\n",
    "- `Rename` can also be used to move files; technically, the full syntax is `os.rename(old_filepath, new_filepath)`.\n",
    "- However, if the old and new file remain in the same folder, we can rely on relative filepaths and just use `old_name`, `new_name`.\n",
    "\n",
    "For example:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "# Let's write a silly file\n",
    "with open(\"temp.txt\", \"w+\") as f:\n",
    "    f.write(\"This is a test file\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "print(f\"Is 'temp.txt' in the directory? {'temp.txt' in os.listdir()}\")\n",
    "print(f\"Is 'temporary.txt' in the directory? {'temporary.txt' in os.listdir()}\")\n",
    "\n",
    "print(\"\\nRenaming now...\\n\")\n",
    "os.rename('temp.txt', 'temporary.txt')\n",
    "\n",
    "print(f\"Is 'temp.txt' in the directory? {'temp.txt' in os.listdir()}\")\n",
    "print(f\"Is 'temporary.txt' in the directory? {'temporary.txt' in os.listdir()}\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**Exercise:** Let's write two more files(\"temp2.txt\" and \"temp3.txt\") and move our temp files from `notes` to `practice_files` using a loop and relative filepaths. Recall that the names of the files (after our renaming) are:\n",
    "\n",
    "      [\"temporary.txt\", \"temp2.txt\", \"temp3.txt\"]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "# Your code here"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**Answer**: <span style=\"color:white\">\n",
    "\\# Create files\n",
    "with open(\"temp2.txt\", \"w+\") as f:\n",
    "    f.write(\"This is a test file\")\n",
    "with open(\"temp3.txt\", \"w+\") as f:\n",
    "    f.write(\"This is a test file\")    \n",
    "\\# Loop through the files we created\n",
    "for f in [\"temporary.txt\", \"temp2.txt\", \"temp3.txt\"]:    \n",
    "    \\# Define the old and new filepaths\n",
    "    old_name = f\n",
    "    new_name = \"practice_files/\" + f    \n",
    "   \\ # Move the files\n",
    "    os.rename(old_name, new_name)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false,
    "scrolled": true
   },
   "outputs": [],
   "source": [
    "# Check our answer:\n",
    "# Go to practice files\n",
    "os.chdir(\"practice_files/\")\n",
    "\n",
    "# Confirm that we're there\n",
    "print(\"Ok. We are now in directory:\")\n",
    "print(os.getcwd())\n",
    "\n",
    "# See what's here -> the moved files\n",
    "print(\"\\nThe contents of this directory are:\")\n",
    "print(os.listdir())"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Removing files\n",
    "Finally, we can get rid of junk using `os.remove()` and `os.rmdir()`. \n",
    "\n",
    "Note:\n",
    "- You will get an error if you remove a non-empty directory, so typically, you will want to empty a directory before deleting it.\n",
    "- You can override this using recursive methods that search inside the directory structure and delete its contents for you. **However, this can be dangerous!!!** You should be extremely careful when using these types of commands.\n",
    "\n",
    "\n",
    "Let's remove the files we created in this notebook, and then remove the `practice_files` directory."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "for fname in [ 'temporary.txt','temp2.txt', 'temp3.txt']:\n",
    "    try:\n",
    "        os.remove(fname)      # Remove each of our files in \"practice_files\"    \n",
    "    except:\n",
    "        print(f\"Couldn't find {fname}\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "os.chdir('../')               # Navigate up to the parent directory\n",
    "os.rmdir('practice_files/')   # Remove the empty \"practice_files\" folder"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "There are many helpful operations you can perform on files with Python, including: downloading them from the internet, unzipping them, etc. We will see some of these operations in the coming notebooks."
   ]
  }
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