# Why is partial_fraction a method but not a function?

Why is partial_fraction a method but not a function? non-function names don't show up in a Tab search so they're hard to recall. Is there a pattern to whether something is a method, a function, or both so I'd know how to search?

The partial_fraction method is bound to something that has in a natural way a "partial fraction". If the choice is to make this method, partial_fraction, global, or to take back the functionality of factor in factor( 77 ) and / or factor( x^3 + y^3 ), then my choice is to take back. Sage comes with an iron python interpreter, hitting the tab "TAB" in it after - say

gives a list of all methods. Alternatively,

`dir(a)`

gives the list of the methods as a list of strings.In our case, taking

`f`

to be a fraction, guessing that there would be a partial fraction method starting with "par", it is enough to try...(There was a TAB after

`f.par`

)I am unable to answer

whythis is the case. But more generally, SageMath is written in an object-oriented manner, meaning that in some sense, all the functionalities are provided through methods. One (mathematical) reason for this choice is that a method only makes sense for some kinds (or types) of objects: It make sense to to compute the partial fraction expansion of $x^4/(x^3+1)$ and to compute the floor of $\pi$, but not vice-versa. I see the existence of functions in SageMath more as an anomaly, though a very handy one, than as the rule.To answer more specifically your last question: Every function actually calls a method on the object it is applied to, usually with the same name. In other words, you can completely ignore functions if you want!