The Python Oracle

'id' is a bad variable name in Python

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Chapters
00:00 'Id' Is A Bad Variable Name In Python
00:12 Accepted Answer Score 195
00:39 Answer 2 Score 64
00:59 Answer 3 Score 62
02:09 Answer 4 Score 119
02:41 Thank you

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Full question
https://stackoverflow.com/questions/7755...

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Content licensed under CC BY-SA
https://meta.stackexchange.com/help/lice...

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Tags
#python

#avk47


ACCEPTED ANSWER

Score 195


id() is a fundamental built-in:

Help on built-in function id in module __builtin__:

id(...)

    id(object) -> integer

    Return the identity of an object.  This is guaranteed to be unique among
    simultaneously existing objects.  (Hint: it's the object's memory
    address.)

In general, using variable names that eclipse a keyword or built-in function in any language is a bad idea, even if it is allowed.



ANSWER 2

Score 119


In PEP 8 - Style Guide for Python Code, the following guidance appears in the section Descriptive: Naming Styles :

  • single_trailing_underscore_ : used by convention to avoid conflicts with Python keyword, e.g.

    Tkinter.Toplevel(master, class_='ClassName')

So, to answer the question, an example that applies this guideline is:

id_ = 42

Including the trailing underscore in the variable name makes the intent clear (to those familiar with the guidance in PEP 8).



ANSWER 3

Score 64


I might say something unpopular here: id() is a rather specialized built-in function that is rarely used in business logic. Therefore I don't see a problem in using it as a variable name in a tight and well-written function, where it's clear that id doesn't mean the built-in function.



ANSWER 4

Score 62


id is a built-in function that gives the identity of an object (which is also its memory address in CPython). If you name one of your functions id, you will have to say builtins.id to get the original (or __builtins__.id in CPython). Renaming id globally is confusing in anything but a small script.

However, reusing built-in names as variables isn't all that bad as long as the use is local. Python has a lot of built-in functions that (1) have common names and (2) you will not use much anyway. Using these as local variables or as members of an object is OK because it's obvious from context what you're doing:

Example:

def numbered(filename):
    with open(filename) as file:
        for i, input in enumerate(file):
            print("%s:\t%s" % (i, input), end='')

Some built-ins with tempting names: