How would I go about writing python functions that can be append to strings (or other object)?
for example:
"FOO".lower()
How do they receive input? Are they generators?
I will happily read up on it, but I don't really know what I am looking for.
Strings are objects and thus have methods. lower() is one of them.
You cannot add a custom method to str, unicode or any other builtin (written in C) classes - see Implementing a custom string method and Extending builtin classes in python
They are not generators. They are simply methods defined on the string class.
You could create your own like this:
>>> class MyString(str):
... def reversed(self):
... return self[::-1]
...
>>> x = MyString('spam and eggs')
>>> x.reversed()
'sgge dna maps'
