Using f-string inside a method

Question

I have code that looks like this:

from dataclasses import dataclass

@dataclass
class Example:
    a: str
    b: str
    c: str
    
    def repeated_code(self):
        if self.c == 'A':
            if self.a != "":
                print(f"as {self.c = } and {self.a = }, set self.a to ''")
                self.a = ""

        if self.c == 'B':
            if self.b != "":
                print(f"as {self.c = } and {self.b = }, set self.b to ''")
                self.b = ""

but I have many similar cases (> 10) in repeated code. I want to refactor this. I'm thinking about this:

@dataclass
class Example2:
    a: str
    b: str
    c: str
    
    def repeated_code(self):
        if self.c == 'A':
            if self.a != "":
                self.log_and_set(self.a, "", self.c)
              
        if self.c == 'B':
            if self.b != "":
                self.log_and_set(self.b, "", self.c)

    def log_and_set(self, a, a_value, c):
        print(f"as {c = } and {a = }, set {a} to ''")
        a = a_value

But:

Setting new value doesn't work in log_and_set (may be able to solve this, not too worried about this).
The printing is all wrong! I would like to print the b values when using the b variable and the a values otherwise, is there a way to do this using f-strings?

Can you show your desired instantiation of this class and expected interaction and output? It isn't clear to me exactly what you're after. — theherk, May 16 '23 at 14:46
@tomgalpin I think in `log_and_set`, `a` could be either `self.a` or `self.b`. — mkrieger1, May 16 '23 at 14:47

score 2 · Accepted Answer · answered May 16 '23 at 15:05

If I'm understanding you correctly, maybe this will be helpful. This uses getattr and setattr to set based on a string given to log_and_set. It also uses a simplified empty check since you know the types are str.

#!/usr/bin/env python
from dataclasses import dataclass


@dataclass
class Example3:
    a: str
    b: str
    c: str

    def repeated_code(self):
        if self.c == "A" and not self.a:
            self.log_and_set("a")

        if self.c == "B" and not self.b:
            self.log_and_set("b")

    def log_and_set(self, x):
        print(f"as {self.c = } and {x} = '{getattr(self, x)}', set {x} to ''")
        setattr(self, x, "")


if __name__ == "__main__":
    ex_a = Example3("", "", "A")
    ex_a.repeated_code()

    ex_b = Example3("", "", "B")
    ex_b.repeated_code()

This prints:

ᐅ ./main.py
as self.c = 'A' and a = '', set a to ''
as self.c = 'B' and b = '', set b to ''

Using f-string inside a method

1 Answers1