A Character TD’s Random Thoughts…

So as one of my first posts I thought I would publish something on one of the reasons I like python over MEL. In C++ there something called function overloading. Which means you can create a function with the same name but different argument types and number of arguments. For example:

int foo( int varA )
{
    return (varA * 2);
}

double foo( double varA, int varB )
{
    return (varA * varB);
}

In the above C++ example you can pass foo an int which is valid or pass foo a double and an int which is valid.

So getting back to MEL and Python, MEL has strongly typed variables like C++ and no general way to overload functions. You could pass your procedure a string array and maybe have the first argument say what to do with that string array, but in the end your still passing and only can pass a string array to that variable.

In Python there is no way to create completely separate overload functions, but you can create a function that receive different types of variables and does completely separate actions based on what types it receives. For example:

import maya.cmds as cmds

# notice that varA and varB are not declared so they can receive any type of variable
def add( varA, varB ):	

	# use the type function to get the variable types and use the
	vAType = type( varA )
	vBType = type( varB )

	# in these cases you would not even need this function adding two string's
	#, float's, int's, list's already works
	if vAType == type(str()) and vBType == type(str()):		return (varA + varB)
	elif vAType == type(int()) and vBType == type(int()): 		return (varA + varB)
	elif vAType == type(float()) and vBType == type(float()):	return (varA + varB)
	elif vAType == type(list()) and vBType == type(list()):		return (varA + varB)

	################################################
	# here is where overloading a function can help
	################################################

	# if varA is an int and varB is not
	elif vAType == type(int()): 

		# normaly if you add a int to a float with python it changes the int to a float
		# this makes it so if you add an int to a float it stays an int
		if vBType == type(float()): 	return (varA + int(varB))

	# if varA is a string and varB is not
	elif vAType == type(str()):

		if vBType == type(int()):		return (varA + str(varB))
		elif vBType == type(float()):		return (varA + str(varB))

		# int the case of the list we need something more
		elif vBType == type(list()):

			result = varA

			# iterate through the list items
			for v in varB:

				# if a list item is a certain type add it to the varA string
				if type(v) == type(str()) or type(v) == type(float()) or type(v) == type(int()):
					result = ( result + str(v) )
			return result

	# nothing matched so return None
	return

Try and execute this script in the Maya script editor then enter these commands:

add( 1, 5 )
add( 'test' , ['one', 2, 3.0] )
add( 'test' , 1.567 )
add( 1, 1.567 )

Your results will be:

# 6
# test1.567
# testone23.0
# 2

In the above example I add like types together and also add types that normaly would not be capable of being added together with just the + operator. Now you would not necesarly want to do this to make a giant add anything function, but you might want to create a function that can receive different data types and do similar operations with them based on the type they are.

-RyanT