Do you use the get/set pattern (in Python)?
Question:
Using get/set seems to be a common practice in Java (for various reasons), but I hardly see Python code that uses this.
Why do you use or avoid get/set methods in Python?
Answers:
Cool link: Python is not Java 🙂
In Java, you have to use getters and setters because using public fields gives you no opportunity to go back and change your mind later to using getters and setters. So in Java, you might as well get the chore out of the way up front. In Python, this is silly, because you can start with a normal attribute and change your mind at any time, without affecting any clients of the class. So, don’t write getters and setters.
No, it’s unpythonic. The generally accepted way is to use normal data attribute and replace the ones that need more complex get/set logic with properties.
Here is what Guido van Rossum says about that in Masterminds of Programming
What do you mean by "fighting the language"?
Guido: That usually means that they’re
trying to continue their habits that
worked well with a different language.
[…] People will turn everything into
a class, and turn every access into an
accessor method,
where that is really not a wise thing to do in Python;
you’ll have more verbose code that is
harder to debug and runs a lot slower.
You know the expression "You can write
FORTRAN in any language?" You can write Java in any language, too.
Your observation is correct. This is not a normal style of Python programming. Attributes are all public, so you just access (get, set, delete) them as you would with attributes of any object that has them (not just classes or instances). It’s easy to tell when Java programmers learn Python because their Python code looks like Java using Python syntax!
I definitely agree with all previous posters, especially @Maximiliano’s link to Phillip’s famous article and @Max’s suggestion that anything more complex than the standard way of setting (and getting) class and instance attributes is to use Properties (or Descriptors to generalize even more) to customize the getting and setting of attributes! (This includes being able to add your own customized versions of private, protected, friend, or whatever policy you want if you desire something other than public.)
As an interesting demo, in Core Python Programming (chapter 13, section 13.16), I came up with an example of using descriptors to store attributes to disk instead of in memory!! Yes, it’s an odd form of persistent storage, but it does show you an example of what is possible!
Here’s another related post that you may find useful as well:
Python: multiple properties, one setter/getter
In python, you can just access the attribute directly because it is public:
class MyClass:
def __init__(self):
self.my_attribute = 0
my_object = MyClass()
my_object.my_attribute = 1 # etc.
If you want to do something on access or mutation of the attribute, you can use properties:
class MyClass:
def __init__(self):
self._my_attribute = 0
@property
def my_attribute(self):
# Do something if you want
return self._my_attribute
@my_attribute.setter
def my_attribute(self, value):
# Do something if you want
self._my_attribute = value
Crucially, the client code remains the same.
The short answer to your question is no, you should use properties when needed. Ryan Tamyoko provides the long answer in his article Getters/Setters/Fuxors
The basic value to take away from all this is that you want to strive to make sure every single line of code has some value or meaning to the programmer. Programming languages are for humans, not machines. If you have code that looks like it doesn’t do anything useful, is hard to read, or seems tedious, then chances are good that Python has some language feature that will let you remove it.
Our teacher showed one example on class explaining when we should use accessor functions.
class Woman(Human):
def getAge(self):
if self.age > 30:
return super().getAge() - 10
else:
return super().getAge()
I had come here for that answer(unfortunately i couldn’t) . But i found a work around else where . This below code could be alternative for get .
class get_var_lis:
def __init__(self):
pass
def __call__(self):
return [2,3,4]
def __iter__(self):
return iter([2,3,4])
some_other_var = get_var_lis
This is just a workaround . By using the above concept u could easily build get/set methodology in py too.
Using get/set seems to be a common practice in Java (for various reasons), but I hardly see Python code that uses this.
Why do you use or avoid get/set methods in Python?
Cool link: Python is not Java 🙂
In Java, you have to use getters and setters because using public fields gives you no opportunity to go back and change your mind later to using getters and setters. So in Java, you might as well get the chore out of the way up front. In Python, this is silly, because you can start with a normal attribute and change your mind at any time, without affecting any clients of the class. So, don’t write getters and setters.
No, it’s unpythonic. The generally accepted way is to use normal data attribute and replace the ones that need more complex get/set logic with properties.
Here is what Guido van Rossum says about that in Masterminds of Programming
What do you mean by "fighting the language"?
Guido: That usually means that they’re
trying to continue their habits that
worked well with a different language.[…] People will turn everything into
a class, and turn every access into an
accessor method,
where that is really not a wise thing to do in Python;
you’ll have more verbose code that is
harder to debug and runs a lot slower.
You know the expression "You can write
FORTRAN in any language?" You can write Java in any language, too.
Your observation is correct. This is not a normal style of Python programming. Attributes are all public, so you just access (get, set, delete) them as you would with attributes of any object that has them (not just classes or instances). It’s easy to tell when Java programmers learn Python because their Python code looks like Java using Python syntax!
I definitely agree with all previous posters, especially @Maximiliano’s link to Phillip’s famous article and @Max’s suggestion that anything more complex than the standard way of setting (and getting) class and instance attributes is to use Properties (or Descriptors to generalize even more) to customize the getting and setting of attributes! (This includes being able to add your own customized versions of private, protected, friend, or whatever policy you want if you desire something other than public.)
As an interesting demo, in Core Python Programming (chapter 13, section 13.16), I came up with an example of using descriptors to store attributes to disk instead of in memory!! Yes, it’s an odd form of persistent storage, but it does show you an example of what is possible!
Here’s another related post that you may find useful as well:
Python: multiple properties, one setter/getter
In python, you can just access the attribute directly because it is public:
class MyClass:
def __init__(self):
self.my_attribute = 0
my_object = MyClass()
my_object.my_attribute = 1 # etc.
If you want to do something on access or mutation of the attribute, you can use properties:
class MyClass:
def __init__(self):
self._my_attribute = 0
@property
def my_attribute(self):
# Do something if you want
return self._my_attribute
@my_attribute.setter
def my_attribute(self, value):
# Do something if you want
self._my_attribute = value
Crucially, the client code remains the same.
The short answer to your question is no, you should use properties when needed. Ryan Tamyoko provides the long answer in his article Getters/Setters/Fuxors
The basic value to take away from all this is that you want to strive to make sure every single line of code has some value or meaning to the programmer. Programming languages are for humans, not machines. If you have code that looks like it doesn’t do anything useful, is hard to read, or seems tedious, then chances are good that Python has some language feature that will let you remove it.
Our teacher showed one example on class explaining when we should use accessor functions.
class Woman(Human):
def getAge(self):
if self.age > 30:
return super().getAge() - 10
else:
return super().getAge()
I had come here for that answer(unfortunately i couldn’t) . But i found a work around else where . This below code could be alternative for get .
class get_var_lis:
def __init__(self):
pass
def __call__(self):
return [2,3,4]
def __iter__(self):
return iter([2,3,4])
some_other_var = get_var_lis
This is just a workaround . By using the above concept u could easily build get/set methodology in py too.