getattr vs eval

you can't write object.x, because you don't know in advance which attribute you want (it comes from a string). Very useful for meta-programming.

Objects in Python can have attributes -- data attributes and functions to work with those (methods). Actually, every object has built-in attributes.

For example you have an object person, that has several attributes: name, gender, etc.

You access these attributes (be it methods or data objects) usually writing: person.name, person.gender, person.the_method(), etc.

But what if you don't know the attribute's name at the time you write the program? For example you have attribute's name stored in a variable called attr_name.

if

attr_name = 'gender' then, instead of writing

gender = person.gender you can write

gender = getattr(person, attr_name)

class Person():
...     name = 'Victor'
...     def say(self, what):
...         print(self.name, what)
... 
>>> getattr(Person, 'name')
'Victor'
>>> attr_name = 'name'
>>> person = Person()
>>> getattr(person, attr_name)
'Victor'
>>> getattr(person, 'say')('Hello')
Victor Hello

  File "<ipython-input-1-c0033f5de77d>", line 13
    Victor Hello
               ^
SyntaxError: invalid syntax

x= hash((1,2)
x

  File "<ipython-input-5-b45d1d86958e>", line 2
    x
    ^
SyntaxError: invalid syntax