Python Fundamentals

#Function Definition
def function_name(param1,param2=default_value..):
	...	
	...
	return value	

Note:

• Any arguments with defaults must come after any arguments that do not have a default value.
• In Python, variables are not passed by reference or by value, instead the name (i.e.object reference) is passed. If the underlying object is mutable , then modifications to the object (within the function) will persist. If the underlying object is immutable, then changes to the variable will not persist. In the below example, the address of a and x (initially, before the change) are the same, however, this isn't pass by reference. Once we change the value of x within the function, it has a new address in memory, i.e. it's a different object.

def func(x):
	print(f'Address of x is {id(x)}') #1234
	x += 10	
	print(f'Address of x is {id(x)}') #7890 -->Address has changed

a = 10
print(f'Address of a is {id(a)}) #1234
func(a)
print(f'Address of a is {id(a)}) #1234

In summary:

• If you pass immutable arguments (numbers, strings, tuples) to a function, the passing is like call-by-value because you can not change the value of the immutable objects being passed to the function.
• If you pass mutable arguments (lists) to a function, it can be considered as call by reference because when their values are changed inside the function, then it will also be reflected outside the function.

Keyword Arguments

def function_name(param1,param2):
	.....

#Function Call
function_name(param2=value2, param1=value1)	

Variable Length Arguments

def func(*args):
	if len(args):
		for s in args:
			print(s)	

func('john','mary','aaron')