[Python] - Function , Lambda

1. Function

---

A function is a block of code which only runs when it is called.
You can pass data, known as parameters, into a function.
A function can return data as a result.

• A function Object is mutable(User classes are considered mutable) - https://stackoverflow.com/questions/12076445/are-user-defined-classes-mutable

# create function
def test():
  return "test"
  
# call function
test()

 

1-1) *args Argument

If you do not know how many arguments that will be passed into your function, add a '*' before the parameter name in the function definition

def my_test(*test_data):
    print("test {}".format(test_data[2]) )
    
my_test("12", "34", "56")
> test56

 

1-2) **kwargs Arguement

If you do not know how many keyword arguments that will be passed into your function, add two asterisk: '**'
 before the parameter name in the function definition.

def my_function(**test_data):
  print("test result {} ".format(test_data["test1"]))

my_function(test1 = "12", test2 = "34")

 

1-3) Default Parameter

def my_function(country = "Norway"):
  print("I am from {}".format(country) )
  
 my_function("Korea")

 

1-4) pass statement

function definitions cannot be empty, but if you for some reason have a function definition with no content, put in the pass statement to avoid getting an error.

def myfunction():
  pass

 

2. Lambda

---

A lambda function is a small anonymous function.

Syntax

lambda arguments : expression

# lambda example
x = lambda a : a + 10

# lambda function
def myfunc(n):
  return lambda a : a * n
  
mydoubler = myfunc(2)
mytripler = myfunc(3)

print(mydoubler(11))
> 22

print(mytripler(11))
> 33