# example1
def f():
    # function body
    print("Hello World")

f() # function call

# example 3
def g(n):
    # function body
    tmp = 1
    for i in range(1, n+1 ,1):
        tmp = tmp * i
    return tmp

x = g(5) # function call, 5*4*3*2*1
print(x)

# answer
def f():
    x = 5
    return

y = f() # function call
print(y)

x = 4**0.5
print(x)

y = 2**0.5
print(y)

def get_sqrt(num):
    return num**0.5

print(get_sqrt(4))
print(get_sqrt(2))

import math

print(math.sqrt(4))
print(math.sqrt(2))

# sample answer 1
def swap(a, b):
    c = a
    a = b
    b = c
    return a, b
a = 1
b = 2
a, b = swap(a,b)
print(a ,b)

# exsample answer 3
# without function
a = 1
b = 2
a, b = b, a
print(a, b)

# Global scope
x = 99  # X and f assigned in module: global
def f(y): # Y and Z assigned in function: locals
    # Local scope
    z = x + y # X is a global
    return z

f(1) # function1 in module: result=100

import builtins
dir(builtins)

# Global scope
w = 21  # W and outer assigned in module: global
def outer(x):# X and inner assigned in enclosing function: Enclosing def locals
    def inner(y): # Z, Y assigned in function: local
        z = w + x + y  # W is a global (21+88+1)
        print(z)
    inner(1)
outer(88)

# answer
x = 'Spam'
def func():
    print(x)
    
func()

# answer
x = 'Spam'
def func():
    x = 'HI!'
    
func()
print(x)

# answer
x = 'World'
def func():
    x = 'Hello'
    print(x)
    
func()
print(x)

# answer
w = 22
def outer():
    w = 23
    def inner():
        w = 24
        print('first: ', w)  # first print
    inner()
    print('second: ', w) # second print
    
outer()
print('third: ', w) # third print

# example
x = 88 # Global x
def f(): 
    global x
    x = 99 # Global x: outside def

f()
print(x)

a = 3
print(id(a), id(3)) # id(a) 表示 a 實際的物件記憶體位址

a = [1,2,3]          # 將 a 指到 一個 mutable object (list)
b = a
print(id(a), id(b))  # 可看到這時 a 跟 b 的記憶體位址是一樣的
a[0] = 's'
print(id(a), id(b))  # 可看到這時 a 跟 b 的記憶體位址依舊是一樣的，從頭到尾都沒變化

def f(a): # a is assigned to (references) the passed object
    a = 99 # Changes local variable a only
b = 88 

f(b) # a and b both reference same 88 initially
print(b) # b is not changed

def change_element(b):           # Arguments assigned references to objects
    b[0] = 'spam'                # Changes shared object in place
    
test_list = [1, 2]
copy_list = test_list[:]         # copy a new list

print('before change: test_list:', test_list, '; list_id:', id(test_list))
print('before change: copy_list', copy_list, '; copy_list_id:', id(copy_list))

change_element(copy_list)

print('after change: test_list:', test_list, '; test_list_id:', id(test_list))              # the same id
print('after change: copy_test_list:', copy_list, '; copy_test_list_id:', id(copy_list))    # the same id

# keywords example
def f(x, y, z):
    print(x, y, z)
    
# In real cases, we should not change the order of the argument names. It is hard for other people to understand your code.
f(z=4, y=5, x=6)

# defaults and postional
def f(x, y, z = 3):
    print(x, y, z)

f(4, 5)
f(4, 5, 6)

# varargs collecting, one * for tuple
def f1(*args):
    print(args)

f1(1, 2, 3, 4, 5, 6, 8, 'hello')
f1('how', 'do', 'you', 'do')

def f2(x, y, *args):
    print(x,y)
    print(args)
f2(1,2,3,4,5,6,8,'hello')

# mix varargs collecting
def mix(x, y, *args, **kwargs):
    print(x,y)
    print(args)
    print(kwargs)
mix(1, 2, 3, 4, 5, 6, 8, 'hello', key1=1, key2=2, key3=3)

# Varargs unpacking 
def f(x, y, z):
    print(x, y, z)
    
some_args=(1, 2, 3)
f(*some_args)

some_kwargs = {'x': 1, 'y': 2, 'z': 3}
f(**some_kwargs)

# example
# What is the output of the following code？
def f1(a, b=4, c=5):
    print(a, b, c)
f1(1, 2)

def f2(a, b, c=5): 
    print(a, b, c)
f2(1, c=3, b=2)

def f3(a, *args):
    print(a, args)
f3(1, 2, 3)

def f4(a, **kargs): 
    print(a, kargs)
f4(a=1, c=3, b=2)

def f5(a, b, c=3, d=4): 
    print(a, b, c, d)
f5(1, *(5, 6))