def hi(name="yasoob"):
return "hi " + name
print(hi())
# output: 'hi yasoob'
# 我們甚至可以將一個函數賦值給一個變量，比如
greet = hi
# 我們這里沒有在使用小括號，因為我們并不是在調用hi函數
# 而是在將它放在greet變量里頭。我們嘗試運行下這個
print(greet())
# output: 'hi yasoob'
# 如果我們刪掉舊的hi函數，看看會發生什么！
del hi
print(hi())
#outputs: NameError
print(greet())
#outputs: 'hi yasoob'

def hi(name="yasoob"):
print("now you are inside the hi() function")

def greet():
return "now you are in the greet() function"

def welcome():
return "now you are in the welcome() function"

print(greet())
print(welcome())
print("now you are back in the hi() function")

hi()
#output:now you are inside the hi() function
# now you are in the greet() function
# now you are in the welcome() function
# now you are back in the hi() function

# 上面展示了無論何時你調用hi(), greet()和welcome()將會同時被調用。
# 然后greet()和welcome()函數在hi()函數之外是不能訪問的，比如：
greet()
#outputs: NameError: name 'greet' is not defined

def hi(name="yasoob"):
def greet():
return "now you are in the greet() function"
def welcome():
return "now you are in the welcome() function"
if name == "yasoob":
return greet #這里！！
else:
return welcome
a = hi()
print(a)
#outputs: <function greet at 0x7f2143c01500>
#上面清晰地展示了`a`現在指向到hi()函數中的greet()函數
#現在試試這個
print(a())
#outputs: now you are in the greet() function

def hi():
return "hi yasoob!"
def doSomethingBeforeHi(func):
print("I am doing some boring work before executing hi()")
print(func())
doSomethingBeforeHi(hi)
#outputs:I am doing some boring work before executing hi()
# hi yasoob!

def a_new_decorator(a_func):
def wrapTheFunction():
print("I am doing some boring work before executing a_func()")
a_func()
print("I am doing some boring work after executing a_func()")
return wrapTheFunction
@a_new_decorator
def a_function_requiring_decoration():
"""Hey you! Decorate me!"""
print("I am the function which needs some decoration to "
"remove my foul smell")

a_function_requiring_decoration()
#outputs: I am doing some boring work before executing a_func()
# I am the function which needs some decoration to remove my foul smell
# I am doing some boring work after executing a_func()
#the @a_new_decorator is just a short way of saying:
a_function_requiring_decoration = a_new_decorator(a_function_requiring_decoration)

def a_new_decorator(a_func):
def wrapTheFunction():
print("I am doing some boring work before executing a_func()")
a_func()
print("I am doing some boring work after executing a_func()")
return wrapTheFunction

def a_function_requiring_decoration():
print("I am the function which needs some decoration to remove my foul smell")

a_function_requiring_decoration()
#outputs: "I am the function which needs some decoration to remove my foul smell"
a_function_requiring_decoration = a_new_decorator(a_function_requiring_decoration)
#now a_function_requiring_decoration is wrapped by wrapTheFunction()
a_function_requiring_decoration()
#outputs:I am doing some boring work before executing a_func()
# I am the function which needs some decoration to remove my foul smell
# I am doing some boring work after executing a_func()

print(a_function_requiring_decoration.__name__)
# Output: wrapTheFunction

from functools import wraps
def a_new_decorator(a_func):
@wraps(a_func)
def wrapTheFunction():
print("I am doing some boring work before executing a_func()")
a_func()
print("I am doing some boring work after executing a_func()")
return wrapTheFunction
@a_new_decorator
def a_function_requiring_decoration():
"""Hey yo! Decorate me!"""
print("I am the function which needs some decoration to "
"remove my foul smell")
print(a_function_requiring_decoration.__name__)
# Output: a_function_requiring_decoration

class Timer:
def __init__(self, value = 0.0):
self._time = value
self._unit = 's'
# 使用裝飾器的時候，需要注意：
# 1. 裝飾器名，函數名需要一直
# 2. property需要先聲明，再寫setter，順序不能倒過來
@property
def time(self):
return str(self._time) + ' ' + self._unit
@time.setter
def time(self, value):
if(value < 0):
raise ValueError('Time cannot be negetive.')
self._time = value
t = Timer()
t.time = 1.0
print(t.time)