Lesson 25

Here we’re getting into writing programs to be used, actually used, on the command line, and that is so exciting. It’s been almost seven months since I made something to actually use, and while I have no real need for a sentence sorter, to have written a program that I can then manipulate in the py shell is REALLY REALLY NEAT, to me.

At first, I struggled a bit with some of the definitions, but I really enjoy separating the definitions from the actual what-you-want-it-to-do-ness of the program, as it were 🙂

Seeing this:
def print_first_word(words):
"""Prints the first word after popping it off."""
word = words.pop(0)
print word

def print_last_word(words):
"""Prints the last word after popping it off."""
word = words.pop(-1)
print word

was pretty exciting, as I recall the idea of “pop”ping from the approximate third of Douglas Hofstadter’s Gödel, Escher, Bach: An Eternal Golden Braid that I read, in one of the interchapter dialogues. Pushing and popping have a very clear analogue in computer science, and while, looking at this particular exercise of Mr Shaw’s, I think that it is not actually the same idea, ha ha! it is still a nice callback even if unintentional and unrelated!

One of the Common Student Questions for this exercise, too, was “what is the difference between print and return, and his answer is somewhat crummy, emphasis mine:

When should I print vs. return in a function?
You need to understand that print is only for printing to the screen and that you can actually do both print and return a value. When you understand this then you'll see that the question is kind of a pointless question. You use print when you want to print. You use return when you want to return.

So I do not really have a clear idea. It seems like once the function has done f(banana) to the stuff, you can either return the result or print it. return seems more verb-y, but the end result seems identical. I will have to read about this!

As a whole this was not a challenging exercise, but it was really fun. I love that Zed Shaw focuses on being able to manipulate python via the structure-level command line rather than via an IDE, like the very popular IDLE which I will not link here. I’ve never imported a function in the shell to play with, and I feel like the possibilities have just expanded. Yeah!

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2 thoughts on “Lesson 25

  1. If it’s the same as C/C++, printing should output to the screen, whereas returning should pass a variable back out of the fubction to where it was called. For example:

    Int foo;
    foo = myfunction();

    Would set foo equal to whatever myfunction returned, as long as myfunction returned an integer in this case.

    I agree, that is a really crummy worded explanation.

    • Oh that’s a very simple explanation, ok, neat! For its programming functionality, basically it sounds like RETURN can eat things and spit them out on command, where PRINT, well, yeah 🙂

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