4. User defined Function

Question 1

basic structure

Answer 1

def myname_of_function(arg1,arg2):
    return arg1 + arg2

Question 2

default an argument

Answer 2

def my_function(name = ‘Default’):

Question 3

indefinite arguments in a func

Answer 3

def myfunc(*args):
    print(args)

args return back a tuple

Question 4

key word argument

Answer 4

def myfunc(**kwargs):
    if 'fruit' in kwargs:

myfunc(fruit = ‘apple’, veggie = ‘lettuce’)

kwargs return back a dictionary

Question 5

map function

Answer 5

map( function ***no parenthesis, iterables)

map will apply the function into each iterables

Question 6

filter function

Answer 6

filter down an iterables.
function has to return boolean

Question 7

lambda expressions

Answer 7

a function only use one time and will not be called again, without the def or a function name

lambda num:num**2

usually use together with map / filter

Question 8

LEGB rule

Answer 8

local: within in function
-> Enclosing function local ->
global -> built-in

Question 9

global assignment in a function

Answer 9

func():
     global x
    x=50   --> affect globally

try to avoid using global

Question 10

passing function in function

Answer 10

function is first class object

def a(x):
    return "a(%s)" % (x,)

def b(f,x):
    return f(x)

print b(a,10)

Question 11

what is a Generator?

Answer 11

Generator can send back a value and then later resume to pick up where it left off.
thus generate a sequence of values over time instead of storing all of the values in memory
range is a type of generator

it’s all about memory efficient in a for loop.
to see all the values, cast it to a list

Question 12

how to operate generator

Answer 12

next and iter

g = simple_gen()
print(next(g))
print(next(g))

iter turn something iterable into a generator

Question 13

generator comprehension

Answer 13

mylist = [1,2,3,4,5]

gencomp = (x for x in mylist if x > 3)

g = gencomp

note that a generator object is different from a generator function

Question 14

Decorator

Answer 14

@new_decor
def func_needs_decorator():
    print("I want to be decorated!!")

this pass the func_needs_decorator() into a wrapper function “new_decor”. the @ line act as an on/off

function can return function, after assignment it can be called

Question 15

passing a function as an argument

Answer 15

def other(wahtevername):
    print("something")
    print(whatevername())