Delving deeper into Python functions and learning more about them, using Reuven Lerner’s Advanced Python Functions Course
Notes The co_* series of attributes inside the __code__ attribute inside most functions gives a wealth of information about a function. For example, looking up the argcount attribute for some function hello, with hello.__code__.co_argcount will give us the number of arguments hello takes. And doing a hello.__code__.co_varnames will give us a tuple of all the local variables in a function hello.__code__.co_code contains the compiled bytecode for the function. Importing the disassembler import dis and running it on the bytecode, dis.dis(hello) will show us what’s in there. hello.__code__.co_flags keeps a track of whether the function has * arguments or not via a binary switch. (It holds many parameters, one of which is the on/off switch for *args) if said switch is set, the function checks for such arguments at runtime and turns them into a tuple to process. they are set for *args via the hello.__code__co_argcount switch (0/1) and for keyword arguments with the hello.__code__.co_kwonlyargcount switch. the __defaults__ attribute keeps all the functions default variable values. If I don’t supply a value to some parameter, the function will look in here, to see if a default value exists. hello.__defaults__ could hold a last name default, for example, if I want my hello function to work even if no last name was supplied, and it actually expected a full name. do not use mutable defaults. an empty list or dictionary for example. set the default to None first in such case and then create the list when the function runs at runtime. The last thing I learnt about were nested functions. I can nest them two/three/as many levels deep as I wish. Practically, most folks do two or three. When an inner function takes the variables of its enclosure and does something with it and returns stuff…? those kinds of functions are called closures. Learning / Feedback/ Experiences from doing exercises The course so far is Reuven making simple functions and then breaking them down and explaining functionality in painstaking detail. Reuven is an awesome teacher! I would gush about him every post, but then it would get too much 😂. So once per course is good I kept looking at the disassembled code and wondering, what language it was. I still don’t know. My ‘educated’ guess is that it is a level of standard pseudo-assembly code for some phantom standardised processor. Once I had that mental model in mind though, all of it started making a lot more sense. This brought memories of Z80 assembly, I learnt in the mid 90s This was fun to do! Onwards to Advanced Objects! Read all about my Python Functions journey here
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