Can I use the variable name "type" as function argument in Python?

24
votes

Can I use type as a name for a python function argument?

def fun(name, type):
    ....
5
python
The name category can work well if you really don't feel like specifying type of what, such as in foo_type. - Nick Merrill
I would use kind instead of type. The dictionary definitions for this context are almost identical. - Michael Hays

5 Answers

39
votes

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')
7
votes

You 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.

5
votes

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.

2
votes

You can, but you would be masking the built-in name type. So it's better not to do that.

0
votes

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