Can I use type as a name for a python function argument?
def fun(name, type):
....
5 Answers
You can, but you shouldn't. It's not a good habit to use names of built-ins because they will override the name of the built-in in that scope. If you must use that word, modify it slightly for the given context.
While it probably won't matter for a small project that is not using type, it's better to stay out of the habit of using the names of keywords/built-ins. The Python Style Guide provides a solution for this if you absolutely must use a name that conflicts with a keyword:
single_trailing_underscore_: used by convention to avoid conflicts with Python keyword, e.g.Tkinter.Toplevel(master, class_='ClassName')
5 Comments
mjv
BTW, since type is such a generic, oft' overused word, adding a qualifer as in "car_type" or "animal_type" makes for a more self-documenting program anyway
rbp
i used to use
tipe, but I always hated the way it looked. now I use typ
Mengo
@Bloke, i think it make sense to name it like
typ. If u have a class car, u don't want to have a property car_type. A language shouldn't steal generic names.
wjandrea
Extending the advice from PEP 8 to cover builtins, you could use
type_
Kardo Paska
I agree with all others about style. Here is a counter example for more context. From the official python docs:
sys.excepthook(type, value, traceback) docs.python.org/3/library/sys.html#sys.excepthookYou can, and that's fine. Even though the advice not to shadow builtins is important, it applies more strongly if an identifier is common, as it will increase confusion and collision. It does not appear type will cause confusion here (but you'll know about that more than anyone else), and I could use exactly what you have.
1 Comment
Mark Dickinson
+1 for mentioning potential confusion. I think that's a much bigger issue than the technical problem of possibly shadowing a builtin: someone reading the code (even possibly the person who wrote it) might expect
type to refer to the builtin. The chances of accidentally shadowing the builtin type seem small in comparison: it's not used all that often in real code.You can use any non-keyword as an identifier (as long as it's a valid identifier of course). type is not a keyword, but using it will shadow the type built-in.
answered Mar 10, 2010 at 15:16
Ignacio Vazquez-Abrams
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Comments
You can, but you would be masking the built-in name type. So it's better not to do that.
Comments
You can use _type for that. For example:
def foo(_type):
pass
If you use type, you can't use type() in that function. For example:
>>> type('foo')
<type 'str'>
>>> type = 'bar'
>>> type('foo')
Traceback (most recent call last):
File "<input>", line 1, in <module>
TypeError: 'str' object is not callable
1 Comment
wjandrea
It would probably be better to use
type_, like PEP 8 recommends for avoiding conflicts with keywords
categorycan work well if you really don't feel like specifying type of what, such as infoo_type.kindinstead oftype. The dictionary definitions for this context are almost identical.