22: Functions (1 of 2)

And now for the very last “pure programming” lesson of the book: writing functions. This is more or less the final tool in the programmer’s toolkit, and as I’ve learned over my years of teaching, it often causes the most trouble.

Now you might be thinking, “hey waitaminit, we’ve known about functions since all the way back on p. 20. This is something new?” Yes it is. Previously in this book, we’ve done a lot of calling functions – from simple ones like len() and np.append() to complex ones like pd.read_csv() to scipy.stats.chi2_contingency() – that someone else has written for us. By contrast, in this chapter, we look behind the curtain and join the production staff: we write our own functions.

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