Parameter Passing in Python Function

Table of Contents

• 1  Types of parameters
• 2  Types of Arguments
• 3  Type of Passing
• 4  functools

Types of parameters¶

Types of parameter	Where
Formal parameters	parenthesized in the function definition
Actual parameters(arguments)	passed during a function call

Types of Arguments¶

Types of Arguments	Where	If need =	Note
default arguments	at defining functions	Yes	- become optional and rewritable during the function calls. - function_call(non-default arguments, default arguments)
keyword arguments	at function call	Yes	- used to passed values through arguments without matching the order of parameters in the function definition - all the keyword arguments should match the parameters in the function definition.
positional arguments	at function call	No	- values passed through arguments are passed to parameters with matching the order of parameters - function_call(positional arguments, keyword arguments)

Type of Passing¶

Type of Passing	Note	Example
Passing values	- a mix of keyword and positional argument	myfun1(1, 2, 3) myfun1(c = 33, b = 22, a = 11)
Passing a list	- the element in list is passing as positional arguments	L1 = [11,22,33] myfun1(*L1)
Passing a dict	- the dict's key should match the formal paramter in the function definition.	d1 = {"c":33, "b":22, "a":11} myfun1(**d1)

functools¶

functools	Note	example
functools.partial() functools.partialmethod()	- usefull in optimization - partially pass/override arguments with keyword arguments.	def objfun1(power, x, y) return (x**power - y)**2 objfun2 = functools.partial(objfun1, x=[1, 2, 3, 4, 5] )
functools.reduce()	- run function over a list, and reduce to one	functools.reduce(lambda x, y: x+y, [1, 2, 3, 4, 5], 20)

Reference:

• 5 Types of Arguments in Python Function Definitions