def __init__(): -- no error

[mmkw43]

I don't know if it means anything to anybody but I had the initialize method in one of my classes with just one underscore each by mistake (rather than 2) and there is no error thrown when you do that. fyi

[DougieLawson]

The one or two underscores is a convention not a syntax requirement.

http://stackoverflow.com/questions/1301 ... -in-python

[elParaguayo]

I think that's true for your own methods, but there are certain special methods that do need the double underscore before and after (http://www.rafekettler.com/magicmethods.html).

If you use a single underscore for your __init__ method then there won't be a syntax error but the method won't be called when you initialise an instance of your class.

See below.

Code: Select all

In [1]: class TestSingleUnderscore(object):
   ...:     def _init_(self):
   ...:         self.x = 1
   ...:         
In [2]: class TestDoubleUnderscore(object):
   ...:     def __init__(self):
   ...:         self.x = 1
   ...:         
In [3]: single = TestSingleUnderscore()
In [4]: double = TestDoubleUnderscore()
In [5]: single.x
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-5-6a93332d6ce4> in <module>()
----> 1 single.x
AttributeError: 'TestSingleUnderscore' object has no attribute 'x'
In [6]: double.x
Out[6]: 1

The "single" method fails because the "_init_" method has not been run on initialisation, but it has for the "double" hence we are able to retrieve the variable value.

[mmkw43]

yeah -- that's how I found out. anyway, just sharing.