Using setattr() in python

Solution 1:

The Python docs say all that needs to be said, as far as I can see.

setattr(object, name, value)

This is the counterpart of getattr(). The arguments are an object, a string and an arbitrary value. The string may name an existing attribute or a new attribute. The function assigns the value to the attribute, provided the object allows it. For example, setattr(x, 'foobar', 123) is equivalent to x.foobar = 123.

If this isn't enough, explain what you don't understand.

Solution 2:

You are setting self.name to the string "get_thing", not the function get_thing.

If you want self.name to be a function, then you should set it to one:

setattr(self, 'name', self.get_thing)

However, that's completely unnecessary for your other code, because you could just call it directly:

value_returned = self.get_thing()

Solution 3:

Setattr: We use setattr to add an attribute to our class instance. We pass the class instance, the attribute name, and the value. and with getattr we retrive these values

For example

Employee = type("Employee", (object,), dict())

employee = Employee()

# Set salary to 1000
setattr(employee,"salary", 1000 )

# Get the Salary
value = getattr(employee, "salary")

print(value)

Solution 4:

Suppose you want to give attributes to an instance which was previously not written in code. The setattr() does just that. It takes the instance of the class self and key and value to set.

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

Solution 5:

To add to the other answers, a common use case I have found for setattr() is when using configs. It is common to parse configs from a file (.ini file or whatever) into a dictionary. So you end up with something like:

configs = {'memory': 2.5, 'colour': 'red', 'charge': 0, ... }

If you want to then assign these configs to a class to be stored and passed around, you could do simple assignment:

MyClass.memory = configs['memory']
MyClass.colour = configs['colour']
MyClass.charge = configs['charge']
...

However, it is much easier and less verbose to loop over the configs, and setattr() like so:

for name, val in configs.items():
    setattr(MyClass, name, val)

As long as your dictionary keys have the proper names, this works very well and is nice and tidy.

*Note, the dict keys need to be strings as they will be the class object names.