Using whitespace in class names in Python

Question

The normal way of creating a class in python does not allow for whitespace in the class name.

>>> class Foo Bar(object):
SyntaxError: invalid syntax

However, using the built-in type() function, we can create a class with whitespace in the name:

>>> C = type('Foo Bar', (object,),{})
>>> C
<class '__main__.Foo Bar'>

Is there any risks, or is it considered bad practice using class names with white space?

Answer 1

There is no risk, the class __name__ is a writable attribute and it's not used for anything particularly important - just boring stuff like the repr and the help display.

If you try to assign non-string to it, there is a custom error message, which is strong evidence that Python devs had the chance to restrict to valid identifiers here, and they intentionally chose not to:

>>> class A:
...     pass
... 
>>> A.__name__ = '123Class'
>>> A.__name__ = 123
TypeError: can only assign string to 123Class.__name__, not 'int'

Here is Guido answering a similar question - about whether attribute names should be restricted to valid identifiers:

https://mail.python.org/pipermail/python-dev/2012-March/117441.html

I've spoken out on this particular question several times before; it is a feature that you can use any arbitrary string with getattr() and setattr(). However these functions should (and do!) reject non-strings.

The same reasoning applies to class names (which could also be stored as arbitrary strings in a module namespace). An example use-case for this feature: ensuring there's a consistent mapping between a sequence of class names and some external data source, even if the external data collides with Python reserved words or syntax.