Search code examples
sortingpython-2.x

How does python compare functions?

How come this doesn't rise Attribute error? function object doesn't have any of the comparison methods. Does it use id() somehow?

fun1 = lambda:x
fun2 = lambda:x
print fun1 == fun1 # True
print fun1 == fun2 # False
print fun1 > fun2 # True
print fun1 < fun2 # False
print fun1 > 1 # True

I understand that it compares addresses, but how? Is it some low level hack in to intercept __lt__, __eq__ etc. ?

Solution

  • Function objects do not define their own comparisons or rich comparisons. Instead, they inherit from type objects which implement rich comparisons based on the object's address in memory.

    So yes, it effectively uses addresses just like the built-in id() function does.

    In Python 3, functions are no longer orderable.