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What is Duck Typing




I had originally answered this on Quora and thought that I should also make it available here in my blog for the readers who do not follow Quora (by the way it's a great site and you should follow that 😎).

Duck typing is a concept that says that the “type” of the object is a matter of concern only at runtime and you don’t need to to explicitly mention the type of the object before you perform any kind of operation on that object.

The following example can help in understanding this concept -
  1. def calc(a,b):
  2. return a+b
Now, Python says that for the above function I don’t need to be concerned about the “type” of the objects ‘a’ & ‘b’ and that the type will be taken care of during runtime as long as the objects support the ‘+’ . So, keeping this in mind the above function will work for any “type” of object which supports the operator + i.e. it will return valid values for a string, list or Integer. When I pass the following “types” of object then the function should work-
  1. calc(1,2) → will return 1+2 = 3
  2. calc('hello','world') --> will return hello world
  3. calc([1],[2]) --> will return [1,2]
What we got in the above results?
  • In the first example of 1,2 since python interpreter recognizes these objects as type integer and since the operator + is valid for integers so the function calc returns a valid output of “type”integer 3. Here while passing the objects 1,2 to the function calc we are not defining that these objects are “type” integer as due to duck typing concept in python, the objects 1,2 are interpreted as integers and hence the function calc must return an output of type integer.
  • In the second example we did not explicitly mentioned anywhere that the objects hello & world are of “type” string, but duck typing concept comes into play and the interpreter recognizes these objects as strings during runtime and when these are passed to the function calc then the output should be a valid string ‘hello world’.
  • In the third example also duck typing can be noticed as the “type” of [1] & [2] is interpreted by python as lists and so the operator + should concatenate (which is a valid operation for lists) these two strings into a bigger string.
More about operators here

Now that you know what duck typing is and that it’s one of the powers of Python you can get started in learning the other features of Python and start exploring this programming language. If you found this post helpful and you have any suggestion to improve my blog then do post your comments below.

If you wanna get started in learning Python then why not get started with the python basics chapter. Check out this link to access the Python Basic Chapter for free.
If you want to download a copy of the chapter then purchase the chapter by clicking on the following link.

Additionally you can also bug me on Quora. You can also find me on Twitter or Facebook. So, why wait go ahead and start exploring.

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