Python, the difference between properties with () and without ()

Question

Hello, I may be missing an important detail about how Python works, and I wanted to see if anyone could help clarify. Short story short I needed to obtain a string list of domain values for a certain domain of a featureclass I was using, so I put the following code into python window after looking up the necessary classes/functions I needed to obtain said information. [x for x in arcpy.da.ListDomains(r'Path_To_Geodatabase') if x.name == u'dPubFunctionalClass'][0].codedValues() This gave me the following error: Runtime error Traceback (most recent call last): File "", line 1, in TypeError: 'dict' object is not callable Removing the parenthesis after .codedValues does the trick. My guess is that .codedValues is not a method of the class Domain, but rather just a variable (a dictionary object) stored within that class. Is this why I get an error message when I attempt to type the .codedValues() instead of just .codedValues? Thank you!

JoshuaBixby · Answer

There are several callable types, see "Callable types" under 3. Data model - 3.2 The standard type hierarchy — Python 2.7.15 documentation

HannesZiegler2 · Answer

Hi Joshua, so I take from this that as I guessed, only functions (or methods) are callable, where any function or method followed by () means it is being called. Usually you call a function with input parameters, but some functions don't require parameters. Variables (or properties) are not callable.

Python Programming/Functions - Wikibooks, open books for an open world

JoshuaBixby · Answer

ListDomains—Help | ArcGIS Desktop returns a Domain object; and as you have discovered, codedValues is a property in the Domain class that returns a Python dictionary. Python allows operator chaining when writing expressions, so it is important to understand 5. Expressions — Python 2.7.15 documentation , especially Operator precedence. Since codedValues is a property, your code: [0].codedValues() ‍ is functionally equivalent to: codedValues_dict = [0].codedValues codedValues_dict() ‍‍ Since Python dictionaries are not callable, your code returns a TypeError.