This seems to occur a lot, and was wondering if this was a requirement in the Python language, or merely a matter of convention?
Also, could someone name and explain which functions tend to have the underscores, and why (
From the Python PEP 8 -- Style Guide for Python Code (http://www.python.org/dev/peps/pep-0008/):
the following special forms using leading or trailing underscores are recognized (these can generally be combined with any case convention):
_single_leading_underscore: weak "internal use" indicator. E.g. "from M import *" does not import objects whose name starts with an underscore.
single_trailing_underscore_: used by convention to avoid conflicts with Python keyword, e.g.
__double_leading_underscore: when naming a class attribute, invokes name mangling (inside class FooBar, __boo becomes _FooBar__boo; see below).
__double_leading_and_trailing_underscore__: "magic" objects or attributes that live in user-controlled namespaces. E.g. __init__, __import__ or __file__. Never invent such names; only use them as documented.
Note that names with double leading and trailing underscores are essentially reserved for Python itself: "Never invent such names; only use them as documented".