fastest way to assign variables to python class

Question

say you have a class that looks like this

class class_name():
    def __init__(self,var1, var2, var3, var4, var5):
        self.var1 = var1
        self.var2 = var2
        self.var3 = var3
        self.var4 = var4
        self.var5 = var5

this can get very long. I have already tried to use a for loop and an exec statement but that did not work. is there a shorter way to assign all of the variables to the class?

`dataclasses.dataclass` https://docs.python.org/3/library/dataclasses.html — hjpotter92, Nov 19 '20 at 19:31
You could potentially have the constructor take a list or dict instead of a bunch of individual values. Depends a lot on the context, but when I have a big set of related values I'll usually define them as a `NamedTuple` and pass them around that way. — Samwise, Nov 19 '20 at 19:34
At the point that the list of variables is getting log, one usually switches to using a data structure...a list or a dictionary. (or a NamedTuple, as @Samwise suggests) — CryptoFool, Nov 19 '20 at 19:34

score 3 · Answer 1 · answered Nov 19 '20 at 19:44

That looks like a dataclass.

Assuming your vars are strings you can define a dataclass like this:

from dataclasses import dataclass

@dataclass
class ClassName:
    var1: str
    var2: str
    var3: str
    var4: str
    var5: str

This automatically defines an init method like this:

def __init__(self, var1: str, var2: str, var3: str, var4: str, var5: str):
    self.var1 = var1
    self.var2 = var2
    self.var3 = var3
    self.var4 = var4
    self.var5 = var5

https://docs.python.org/3/library/dataclasses.html

better answer is not accepted answer. hmmm – pratikone Jun 24 '22 at 19:59 — pratikone, Jun 24 '22 at 19:59

wakey · Accepted Answer · 2020-11-19T19:41:02.757

You could do something like this... Although this is pretty magic and not recommended.

class ClassName:
   def __init__(self, **kwargs):
      for key, value in kwargs.items():
         setattr(self, key, value)

Used like

my_class = ClassName(first=1, second=2, third=3)

print(my_class.first)  # 1
print(my_class.second)  # 2
print(my_class.third)  # 3

This requires you to provide all arguments as keyword arguments (e.g. key=value. This will error if you try to create the class with just values and no keys.

# This does not work
my_class = ClassName(1, 2, 3)

Again I have to reiterate that this is not recommended. Letting users of your class know exactly what variables they should be passing in to construct your class is extremely valuable.

This is what I also was thinking, but it would require you to do `myVar = ClassName(var1='a', var2='b')`. You'd have add the parameter names when creating a new object. — gen_Eric, Nov 19 '20 at 19:35

score 0 · Answer 3 · answered Nov 19 '20 at 19:36

0

Use *args-style argument packing.

class class_name():
    def __init__(self, *vars):
        self.vars = vars
        # now you can access self.vars[0], self.vars[1], etc.

answered Nov 19 '20 at 19:36

John Gordon

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fastest way to assign variables to python class

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