Jon's Friendica Node | Jonathan Lamothe @ Jon's Friendica Node

Jonathan Lamothe

me@social.jlamothe.net

Programmer and free/libre software enthusiast. This is my primary account on the Fediverse. See my website for an authoritative list of accounts.
https://jlamothe.net

Ontario, Canada

jlamothe@jabber.sdf.org

https://jlamothe.net ✔

Jonathan Lamothe

8 months ago

Jonathan Lamothe
8 months ago

Been reading up on #Python lately. I know that classes in Python "doesn't support" private values, but could this functionality not be implemented with closures?

Edit: typo

#python

This entry was edited (8 months ago)

Meghana :bongoCat: likes this.

Jonathan Lamothe

8 months ago

Content warning: boring nerd stuff (example code)

I'm on my phone right now and don't have an interpreter handy but I'm thinking something along the lines of:

class Counter:
    def __init__(self):
        count = 0

        def increment(self):
            nonlocal count
            count = count + 1

        def get_count(self):
            nonlocal count
            count

        self.increment = increment
        self.get_count = get_count

Wouldn't this effectively make count into a private variable (granted, one that *couldn't* be inherited)?

There's probably a better way of writing it too.

Zerody likes this.

Gabriel Pettier

8 months ago •

Content warning: boring nerd stuff (example code)

This entry was edited (8 months ago)

Gabriel Pettier

8 months ago •

something like this? Sure the class can save the value in a method and return that later, but then i get the same problem, anything can decide to patch this method instead.

Python class patching its own method to return a different result
```
class ClosureClass:
def set_val(self, value):
self.get_val = lambda: value

def get_val(self):
return "default value"

if __name__ == '__main__':
cl = ClosureClass()
print(cl.get_val())
cl.set_val("another value")
print(cl.get_val())

print(ClosureClass().get_val())
```

running this code displays
```
default value
another value
default value
```

Jonathan Lamothe

8 months ago

@Gabriel Pettier That's even cleaner than what I'd conceptualized, yes.

@Gabriel Pettier

well, it's not very clean, as self modifying code is not a good friend of code that is easy to reason about and maintain, and that will likely confuse type checkers and other tools. And it doesn't solve the problem, since i can totally do cl.get_val = lambda: "test" instead of calling cl.set_val("test").

Jonathan Lamothe

8 months ago

@Gabriel Pettier That's true. It's not what I would consider to be a *good* idea. I was just reading in the docs where it said Python had *no way* of creating private variables, and I thought: Is that *really* true?

At the very least, it's fair to say that there is no official way.

@Gabriel Pettier

Gabriel Pettier likes this.

Maurice LéDuck

8 months ago •

Someone argued that Python is a language for adults and "private" variables are therefore not needed. There will always be ways to access them anyway but responsible programmers would just leave them alone.

Jonathan Lamothe

8 months ago

@Maurice LéDuck I guess. I just hate polluting my namespaces unecessarily.

@Maurice LéDuck

dn

8 months ago •

If the #Python rules and conventions of _ prefixes don't meet the needs for 'privacy', perhaps choose another tool from the tool-box instead of trying to hammer-in a screw?

#python

Jonathan Lamothe

8 months ago

@dn Not my project. I didn't pick the tool.

That said, it was more of a hypothetical question.

@dn

Jonathan Lamothe

8 months ago

Jonathan Lamothe
8 months ago

Want to brush up on my #Python #MySQL and #JavaScript for a technical interview I may or may not get shortly. If anyone has any recommendations for additional resources that might be helpful, I'd be happy to look at them.

#python #javascript #mysql

like this

wing

8 months ago •

For SQL, I found sqlbolt.com/ a bit ago. Has exercises at the bottom of each page, could be useful as a catch up, found it nice myself.

SQLBolt - Learn SQL - Introduction to SQL

SQLBolt provides a set of interactive lessons and exercises to help you learn SQL

^sqlbolt.com

Jonathan Lamothe likes this.

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