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Scraping course schedule data

Topics/tags: The joy of code, Grinnell, technical, schedule, long

Note: The interesting data appear toward the end of this musing. Look for the text It’s time for a table.

The other day, Youngest Son asked whether I knew that you could use Google Sheets to scrape Web data. Michelle looked at us with a bit of confusion, so we explained what it means to scrape Web data and why you might want to do so [1].

A few days later, as I was reflecting on the course timetable and wondering how popular each timeslot is, I realized that I could use Google sheets to gather and extract the data. In this musing, I do my best to document my steps and to report on what I discovered.

First, let’s get the data into the spreadsheet. It turns out that that’s relatively simple, using the IMPORTHTML command. Here’s what I put in cell A1 of my spreadsheet.

=IMPORTHTML("", "table", 1)

And, voila, the data appear. Unfortunately, I only seem to be able to get data for the current semester as the itwebapps CourseOffering page doesn’t have a clear API [2].

Wait a second. I’m a computer scientist; I should be able to figure things out. Ah hah! I can add a query string, and it seems to work. For example, gives me the spring 2019 listings [3]. I can scrape data from both this semester and next semester [4].

Next, I’d like to be able to analyze the data. I suppose it would make sense for me to put them in an SQL database and write appropriate queries. But I’m lazy. So I’m just going to save them in a tab-separated-value file and use Linux command-line tools.

What does one line look like? Here’s an example.

81788       Open    CSC-161-01      Imperative Prblm Solvng w/lab   MWF     8:30 AM - 9:50 AM -     Walker, Henry M 10/28   4

We seem to have the course code (column 0 [5]), a tab, an open/closed/balanced status (column 1), a tab, the course number (column 2), a tab, the course title (column 3), a tab, the days it meets (column 4), a tab, the meeting times (column 5), a tab, the instructor (column 6), a tab, available/capacity (column 7), a tab, and the number of credits (column 8).

Some of those entries are a bit strange because the course meets at multiple times in the week. Here’s an example which meets Monday and Wednesday from 1:00-3:50 p.m. and Friday from 1:00-1:50 p.m. It also has one more field.

82505 Closed BIO-150-01 Intro to Biolgcl Inqry W/Lab MW F 1:00 PM - 3:50 PM 1:00 PM - 1:50 PM Brown, Jonathan M 0/24 4 Yes

I’m going to ignore those complexities for now [6].

My first step is to extract the courses that meet on at least two of Monday, Wednesday, and Friday. I’m going to use egrep, which means that I’ll generate a fairly ugly regular expression.

$ egrep '^([^\t]*\t){4}[MWF]' 2018F.txt

Nope. That didn’t work. While it includes the lines I want, it also includes entries whose weekday column doesn’t start with M, W, or F. I’m not sure why. It may have something to do with the interpretation of tabs [7]. Have I ever mentioned how much I hate computers? I wonder what happens if I replace all the tabs with tildes.

$ cat 2018F.txt | tr '\t' '~' | egrep '^([^~]*~){4}[MWF]'

Yup. That does seem to work. That is, I seem to get only the courses whose weekday column starts with M, W, or F.

Since I’ve written some ugly code, I should probably explain it.

  • tr '\t' '~' translates tabs to tildes.
  • egrep is extended grep, a utility for searching files.
  • The first caret (^) represents the start of the line.
  • The [^~] represents anything but a tilde. Square brackets represent a set. A caret after the left square bracket indicates that it’s an anti-set, anything except the next characters.
  • The asterisk (*) represents zero or more copies.
  • The parentheses group, just as they do in most languages [8]. So ([^~]*~) means a bunch of characters, not including a tilde, and then a tilde. Given the structure of our file, it matches one column.
  • The {4} means four times. Since we put it after something that matches one column, we now match the first four columns.
  • And the [MWF] is, once again, set notation. In this case, it means M, W, or F.

And yes, there are people out there who found the original clear enough that it did not need this explanation.

You know what? I only want courses that meet at least two days per week. So I’m going to change my command a bit, and save the result to a file.

$ cat 2018F.txt | tr '\t' '~' | egrep '^([^~]*~){4}(MTW|MW|WF|MF)' > 2018F-mwf.txt

I can probably create one for the Tuesday/Thursday courses, too.

$ cat 2018F.txt | tr '\t' '~' | egrep '^([^~]*~){4}(TTH)' > 2018F-tth.txt

Now I should think a bit about the content of these files. Did I miss anything by using TTH instead of T TH?

$ cat 2018F.txt | tr '\t' '~' | egrep '^([^~]*~){4}(T TH)'
83072~Open~ALS-100-05~Korean I~T TH~8:00 PM - 9:00 PM 4:30 PM - 5:30 PM~Frances, Claire~2/8~2~

One course, and it’s at a nontraditional time. I can ignore that one in my analysis.

What about courses that meet MWF but also have an extra meeting time (e.g., for lab)?

$ egrep '^([^~]*~){4}([A-Z]* )' 2018F-mwf.txt 
81446~Open~ARB-221-01~Intermediate Arabic I~MWF TH~1:00 PM - 1:50 PM 2:00 PM - 2:50 PM~Hussein, Mona Hamed~16/20~4~
82505~Closed~BIO-150-01~Intro to Biolgcl Inqry W/Lab~MW F~1:00 PM - 3:50 PM 1:00 PM - 1:50 PM~Brown, Jonathan M~0/24~4~Yes
82479~Closed~BIO-251-01~Molcls, Cells, & Orgnsm w/lab~MWF T~3:00 PM - 3:50 PM 1:00 PM - 3:50 PM~Sandquist, Joshua C.~2/24~4~

Oh. There are a bunch. Let’s see how many.

$ egrep '^([^~]*~){4}([A-Z]* )' 2018F-mwf.txt  | wc -l

That’s too many to process by hand. I know! I can eliminate the second time slot so that I don’t have to worry about it in future queries. Let’s see.

$ egrep '^([^~]*~){4}([A-Z]* )' 2018F-mwf.txt | sed -E 's/M [0-9]+:[0-9]+ .M - [0-9]+:[0-9]+ .M/M/'
81446~Open~ARB-221-01~Intermediate Arabic I~MWF TH~1:00 PM - 1:50 PM~Hussein, Mona Hamed~16/20~4~
82505~Closed~BIO-150-01~Intro to Biolgcl Inqry W/Lab~MW F~1:00 PM - 3:50 PM~Brown, Jonathan M~0/24~4~Yes
82479~Closed~BIO-251-01~Molcls, Cells, & Orgnsm w/lab~MWF T~3:00 PM - 3:50 PM~Sandquist, Joshua C.~2/24~4~

That does the trick. The lab times, such as they are, don’t get included. But that’s a pretty horrendous sed command. Can I clean it up?

$ egrep '^([^~]*~){4}([A-Z]* )' 2018F-mwf.txt | sed -E 's/M [0-9]+:[^~]*~/M~/'
81446~Open~ARB-221-01~Intermediate Arabic I~MWF TH~1:00 PM - 1:50 PM~Hussein, Mona Hamed~16/20~4~
82505~Closed~BIO-150-01~Intro to Biolgcl Inqry W/Lab~MW F~1:00 PM - 3:50 PM~Brown, Jonathan M~0/24~4~Yes
82479~Closed~BIO-251-01~Molcls, Cells, & Orgnsm w/lab~MWF T~3:00 PM - 3:50 PM~Sandquist, Joshua C.~2/24~4~

That’s a bit better. Of course, I should probably use that sed command as I generate the two files.

$ cat 2018F.txt | tr '\t' '~' | egrep '^([^~]*~){4}(MTW|MW|WF|MF)' | sed -E 's/M [0-9]+:[^~]*~/M~/' > 2018F-mwf.txt
$ cat 2018F.txt | tr '\t' '~' | egrep '^([^~]*~){4}(TTH)' | sed -E 's/M [0-9]+:[^~]*~/M~/' > 2018F-tth.txt

Oh, yeah. I should ignore the Canceled classes. And I really should include the TWTH courses in the TTH list (at least if I care about those that use up those time slots). Time to clean up my commands a bit.

$ grep -v "\tCanceled\t" 2018F.txt | tr '\t' '~' | sed -E 's/M [0-9]+:[^~]*~/M~/' > 2018F.tmp
$ egrep '^([^~]*~){4}(MTW|MW|WF|MF)' 2018F.tmp > 2018F-mwf.txt 
$ egrep '^([^~]*~){4}(TTH|MTWTH)' 2018F.tmp > 2018F-tth.txt 

At this point, I’m beginning to wonder if I should use a different tool [9]. But I’ve gotten this far, so I’m going to continue.

Let me take stock. I have created two files, 2018F-mwf.txt and 2018F-tth.txt. The first contains all the courses that meet at least two of Monday, Wednesday, and Friday. The second contains all the courses that meet only on Tuesday and Thursday. I don’t think we have any courses that meet Tuesday, Wednesday, and Thursday, except for those that meet all five days [10]. I think I’m ready to gather data.

$ grep "8:00 AM - 8:50 AM" 2018F-mwf.txt | wc -l
$ grep "8:00 AM - 9:50 AM" 2018F-mwf.txt | wc -l

Yup, things look good. It’s time for a table [11].

Slot        Times (MWF)       Number
 1           8:00- 8:50 AM      19
 2           9:00- 9:50 AM      40
 3          10:00-10:50 AM      26
 4          11:00-11:50 AM      34
 5           1:00- 1:50 PM      34
 6           2:00- 2:50 PM       5
 7           3:00- 3:50 PM      20
 8           8:30- 9:50 AM      13
 9          10:00-11:20 AM      12
10           1:00- 2:20 PM      18
11           2:30- 3:50 PM      11
12           8:00- 9:50 AM       7
13          10:00-11:50 AM      11
14           2:00- 3:50 PM      12
15           8:00-10:50 AM      2
16           9:00-11:50 AM      1
17           1:00- 3:50 PM      7

Now, we can combine the data. If I were smarter, I’d write a program.

Times (MWF)         Slots           Count
  8:00- 8:50 AM     1,8,12,15       19+13+7+2 =    41
  9:00- 9:50 AM     2,8,12,16       40+13+7+1 =    61
 10:00-10:50 AM     3,9,13,15,16    26+12+11+2+1 = 52
 11:00-11:50 AM     4,9,13,16       34+12+11+1 =   58
  1:00- 1:50 PM     5,10,17         34+18+7 =      59
  2:00- 2:50 PM     6,10,11,14,17   5+18+11+12+7 = 53
  3:00- 3:50 PM     7,11,14,17      20+11+12+7 =   50

I won’t claim that the count is exact. For example, we do sometimes have classes that meet one day per week for, say, 8:00-10:50 or 9:00-11:50. However, I don’t think there are all that many.

What about the equivalent slots on Tuesday and Thursday? Let’s see.

Slot        Times (TTh)       Number
 1           8:00- 8:50 AM       1
 2           9:00- 9:50 AM       2
 3          10:00-10:50 AM      13
 5           1:00- 1:50 PM       7
 6           2:00- 2:50 PM       2
 7           3:00- 3:50 PM       1
18           8:00- 9:20 AM       4
19           9:30-10:50 AM      14
20           1:00- 2:20 PM      15
21           2:30- 3:50 PM      10
22           8:00- 9:50 AM      38
23           9:00-10:50 AM       3
24           2:00- 3:50 PM      14
25           8:00-10:50 AM       2
26           1:00- 3:50 PM       7

Just in case you’re wondering, the large number of classes in the 8:00-9:50 slot represent offerings of Tutorial.

Now, let’s see what this means for each hour of the day.

Times (TTh)         Slots             Count
  8:00- 8:50 AM     1,18,22,25        1+4+38+2 =     45
  9:00- 9:50 AM     2,18,19,22,23,25  2+4+14+38+3 =  61
 10:00-10:50 AM     3,19,23,25        13+14+3+2 =    32
  1:00- 1:50 PM     5,20,26           7+15+7 =       29
  2:00- 2:50 PM     6,20,21,24,26     2+15+10+14+7 = 48
  3:00- 3:50 PM     7,21,24,26        7+10+14+7 =    38

My imperfect read is that our pressure points are MWF [12] 9:00, 11:00, and 1:00 and TuTh at 9:00. Can a bit of arm twisting solve these issues? It looks like moving a few 9:00 a.m. MWF and 11:00 MWF classes to 10:00 a.m. should solve some problems. We also have a reasonable amount of room on TuTh afternoons. How many two-day-per-week classes meet in the MWF time slot? Sixty meet just MW. Two meet MF. Five meet WF. We could shift a few of those to TuTh afternoons and address some of our problems.

Unfortunately, I’ve just realized that my counting doesn’t deal with cross-listed courses. Maybe I’m better off just asking the Registrar’s office for the data. Still, I’ve gotten a rough picture of the pressure points for this fall.

Postscript: This exercise may seem secondary to my primary digital humanities project. However, many parts relate directly to that project. I should teach my students how to scrape data. Google spreadsheets may be more convenient than the scripts I have them write. I’ll probably have them learn both. And the Scheme library for scraping data needs to be on my to write soon list. Then I’ll rewrite this musing using those tools.

Postscript: Speaking of programs and libraries, I should probably write a program that generates one of those tables by hand. However, if I’m going to do that, I should strive for more reliable results. I wonder if I can find a good way to identify cross-listed courses.

Postscript: I’ve been writing a few joy of code musings. I wonder if I should start a separate joy of data series.

[1] Youngest Son’s college choice spreadsheet has reached a few hundred columns of data. He’s clearly at the point that he wants to fill in those cells by code rather than by hand.

[2] That is, if I change the semester, the URL does not change.

[3] Interestingly, that approach also gives me access to summer listings.

[4] I eventually decided that I didn’t want to analyze next semester, so it doesn’t matter right now. But it’s nice to know that I can get that information if I want it.

[5] As a computer scientist, I tend to start numbering at zero.

[6] I see that the Yes likely means Writing Intensive.

[7] Youngest Son tells me that Mac grep doesn’t handle tabs correctly. I wonder why.

[8] Scheme is a notable exception.

[9] See the postscript for some more reflection.

[10] I used grep "TWTH" 2018F.txt | grep -v "MTWTH" to check.

[11] The slot numbers come from the current timetable.

[12] MWF represents MWF and MW and WF and MF and MTWF and MTWTHF and variants thereof.

Version 1.0 of 2018-10-18.