We are using a dataset with records on inflammation from patients following an arthritis treatment.
We make reference in the lesson that this data is somehow strange. It is strange
because it is fabricated! The script used to generate the inflammation data
is included as tools/gen_inflammation.py.
This lesson is written as an introduction to Python, but its real purpose is to introduce the single most important idea in programming: how to solve problems by building functions, each of which can fit in a programmer’s working memory. In order to teach that, we must teach people a little about the mechanics of manipulating data with lists and file I/O so that their functions can do things they actually care about. Our teaching order tries to show practical uses of every idea as soon as it is introduced; instructors should resist the temptation to explain the “other 90%” of the language as well.
The final example asks them to build a command-line tool
that works with the Unix pipe-and-filter model.
We do this because it is a useful skill
and because it helps learners see that the software they use isn’t magical.
Tools like grep might be more sophisticated than
the programs our learners can write at this point in their careers,
but it’s crucial they realize this is a difference of scale rather than kind.
Explain that we use Python because:
We do not include instructions on running the Jupyter Notebook in the tutorial because we want to focus on the language rather than the tools. Instructors should, however, walk learners through some basic operations:
jupyter notebook.In[#] and Out[#].Watching the instructor grow programs step by step is as helpful to learners as anything to do with Python. Resist the urge to update a single cell repeatedly (which is what you’d probably do in real life). Instead, clone the previous cell and write the update in the new copy so that learners have a complete record of how the program grew. Once you’ve done this, you can say, “Now why don’t we just break things into small functions right from the start?”
The discussion of command-line scripts assumes that students understand standard I/O and building filters, which are covered in the lesson on the shell.
import ... as ... syntax.
This syntax is commonly used in the scientific Python community;
it is explicitly recommended in documentation to import numpy as np
and import matplotlib.pyplot as plt. Despite that, we have decided
not to introduce aliasing imports in this novice lesson due to the
additional cognitive load it puts on students, despite the typing that
it saves. A good summary of arguments for and against can be found in
PR #61.
It is up to you as an individual instructor whether you want to introduce these aliases when you teach this lesson, but we encourage you to please read those arguments thoroughly before deciding one way or the other.
NumPy methods.
We used to use NumPy array methods in the first NumPy topic. We switched these methods to the equivalent functions because a majority of instructors supported the change; see PR #244 for detailed arguments for and against the change.
Underscores vs. hyphens in filenames
We used to use hyphens in filenames in order to signify that these Python
files should only be run as scripts and never imported. However, after some
discussion,
including an informal Twitter poll, we switched over to underscores because
many files that start off as Python scripts end up being imported eventually.
For that reason, we also added if __name__ == '__main__' guards around
main() calls, which is how real-world Python scripts ensure that imports
do not result in side-effects.
After discussing the challenges is a good time to introduce the b *= 2 syntax.