Assignment 7

Goals

The goal of this assignment is to work with the file system, concurrency, and basic data processing in Python.

Instructions

You will be doing your work in Python for this assignment. You may choose to work on this assignment on a hosted environment (e.g. tiger) or on your own local installation of Jupyter and Python. You should use Python 3.9 or higher for your work. To use tiger, use the credentials you received. If you work remotely, make sure to download the .py files to turn in. If you choose to work locally, Anaconda is the easiest way to install and manage Python. If you work locally, you may launch Jupyter Lab either from the Navigator application or via the command-line as jupyter-lab. You may need to install some packages for this assignment: aiohttp (or requests) and pandas. Use the Navigator application or the command line conda install pandas requests to install them.

In this assignment, we will be working with files and threads. We will be using unemployment data from Illinois, available from the Illinois Department of Employment Security. I have downloaded the historical county data, and made it available on the course web site. You will download six zip files from there, extract the archives, load specific files from the archives, fix an issue with county names, and store it by county for some selected counties. You will use threading to download and process the data.

Due Date

The assignment is due at 11:59pm on Friday, April 22.

Submission

You should submit the completed notebook file required for this assignment on Blackboard. The filename of the notebook should be a7.ipynb.

Details

Please make sure to follow instructions to receive full credit. Because you will be writing classes and adding to them, you do not need to separate each part of the assignment. Please document any shortcomings with your code. You may put the code for each part into one or more cells. Note that CS 503 Students must use asyncio which is optional for CS 490 students.

0. Name & Z-ID (5 pts)

The first cell of your notebook should be a markdown cell with a line for your name and a line for your Z-ID. If you wish to add other information (the assignment name, a description of the assignment), you may do so after these two lines.

1. Download & Extract Files

There are six zip files posted on the course web site that you will download using python. Their filenames are unemp-<decade>.zip where <decade> is a decade from 1970 to 2020, inclusive. CSCI 503 students will use aiohttp for this task while CSCI 490 students may use the requests library. (If you have trouble with this part and wish to continue with other parts of the assignment, download the files manually.)

1a. [CSCI 490] Download & Extract Files (20 pts)

To download the files, use the requests library. (This library is installed on tiger, but if you work locally, you may need to install it; conda install requests should work.) Note that each download is a two-step process: first “get”-ing the file and then writing the response to a file. Consult the documentation. After downloading the archives, you should extract all six zip files into the local directory. Remember the DRY principle here. Also, once you download and extract the files into the working directory, rerunning the code to test it may not work as expected because they will already be there. To check for this situation, write code to check (1) if an archive has already been downloaded before downloading it, and (2) if the extracted directory already exists before extracting it. You may also write code to delete those files once to check that your code works, but be careful that you do not delete other files in the process!

Hints
  • Note that when unzipped, each archive will have a named that reflects the decade the data is from.
  • When writing the archive, you will probably want to open the file in binary write mode.
  • Use the exists method with os.path or pathlib.Path to check for path existence
  • Either zipfile or shutil will be useful in extracting the archive.
  • shutil’s rmtree can be used to delete a directory.

1b. [CSCI 503] Download & Extract Files (30 pts)

To download the files, use the aiohttp library and asyncio to download all the files. (This library is installed on tiger, but if you work locally, you may need to install it; conda install aiohttp should work. You may also need to install nest_asyncio via pip.) While you can refer to the example we showed in class, remember that you need to save each file locally after downloading it. This should be handled as a separate async coroutine, but note that the code in the method will be synchronous because operating systems generally do not support asynchronous file I/O. After downloading the archives, you should extract all six zip files into the local directory. This may be done synchronously! Remember the DRY principle here. Also, once you download and extract the files into the working directory, rerunning the code to test it may not work as expected because they will already be there. To check for this situation, write code to check (1) if an archive has already been downloaded before downloading it, and (2) if the extracted directory already exists before extracting it. You may also write code to delete those files once to check that your code works, but be careful that you do not delete other files in the process!

Hints
  • You will probably need to run import nest_asyncio; nest_asyncio.apply() in the notebook
  • Note that when unzipped, each archive will have a name that reflects the decade the data is from.
  • When writing the archive, you will probably want to open the file in binary write mode.
  • Use the exists method with os.path or pathlib.Path to check for path existence
  • Either zipfile or shutil will be useful in extracting the archive.
  • shutil’s rmtree can be used to delete a directory.

2. Find Matching Files (10 pts)

Now, write code to find all files in the unzipped directories that end with the file extension .csv. Note that each directory can have a different name for the files (e.g. employment or unemp) and there are two different formats of the files (csv and xlsx). You should find six csv files in the various subdirectories, and your code should find the paths to those files.

Hints
  • There is more than one way to accomplish this, depending on which libraries you use.
  • Remember that your code needs to check subdirectories.

3. Use Threads to Process Files (30 pts)

Finally, we are going to process all the files using threads via concurrent.futures. Use pandas for the data processing steps. (Again, pandas is installed on tiger, but if you work locally, you may need to install it; conda install pandas should work.) Besides reading the files, we will need to replace some of the county names to agree on a common scheme. Each comma-separated values (csv) file has the columns COUNTY, FIPS, YEAR, LABOR_FORCE, EMPLOYED, UNEMPLOYED_NUMBER, and RATE. Note that each file also has a header with these column names. For each file, extract only the columns COUNTY, YEAR, LABOR_FORCE, EMPLOYED, and UNEMPLOYED_NUMBER. Then,

  1. Convert all values in the COUNTY column to upper-case.
  2. Filter the rows to include only DEKALB, KANE, BOONE, MCHENRY, WINNEBAGO, OGLE, LEE, and KENDALL counties.
  3. Recompute the RATE column by dividing UNEMPLOYED_NUMBER by LABOR_FORCE.

Use a ThreadPoolExecutor to process (read, convert, filter, and recompute) each matching file from Part 2. Take the results from each run, and concatenate them together.

From the single concatenated dataframe, create eight dataframes, one for each county, and write eight files with the county name (e.g. DEKALB.csv.gz) which contain only the records from the specified county. The .gz extension means that the file will be compressed using the gzip algorithm to make the output smaller (pandas will do this automatically if you specify that file extension).

Hints
  • Consider writing the processing function first, then add threading.
  • You will need to go back and forth between counties specified with as “DEKALB COUNTY” and “DEKALB” so consider using a list comprehension to create one from the other.
  • pandas has methods to read and write csv files. The index argument can be useful if you don’t want to write the index.
  • pandas offers selection via boolean indexing similar to numpy.
  • pandas has string methods like upper that should be useful.
  • The isin method can be useful for checking if values match one of the values in a container like a list.
  • Use concurrent.futures to run each thread, and consider the map function to wait for all results to complete

Check Results

While this does not guarantee correct answers, the following code to compute the average unemployment rate over the past 40+ years should produce the corresponding results:

counties_no_suffix = ['DEKALB', 'KANE', 'BOONE', 'MCHENRY', 'WINNEBAGO', 'OGLE', 'LEE', 'KENDALL'] 
for c in sorted(counties_no_suffix):
    cdf = pd.read_csv(f'{c}.csv.gz')
    print(c, cdf.RATE.mean())
BOONE 0.08099938784155404
DEKALB 0.05766694572727062
KANE 0.06465744592318969
KENDALL 0.05521362047852946
LEE 0.06341724493660843
MCHENRY 0.059635399403897664
OGLE 0.0666058153499312
WINNEBAGO 0.07757288231143362