Python3 from zero--{initial consciousness: 007~ function}

To write a function that accepts any number of parameters: *, * *

def Test (x, *args, y, * *Kwargs):   ... Pass  >>> Test (1, 2, 3, 4, 5, 5, y=9, aa=99, bb=88,cc=900)>>> Test (1, 2, 3, 4, 5, 5, 9, aa=9 9, bb=88,cc=900) Traceback (most recent  ):"<stdin>"  in <module>'y'

#以 * The parameter of the beginning can only appear as the last positional parameter, and the argument of the * * will only appear as the last parameter; *args can still have other parameters, but only the keyword parameter (keyword_only)

Second, write functions that accept only keyword parameters

def Test (*, X, y): ...   Pass  >>> Test (8, 9) Traceback (most recent)  :"<stdin> "  in <module>2 were given>>> test (x=9, y=8)

The parameters after #星号 * are keyword_only parameters

Third, function annotation

>>>defAdd (X:int, Y:int)int: ...returnX +y ... Add.__annotations__{'x': <class 'int','return': <class 'int','y': <class 'int'}

#函数注解只会保存在函数的__annotations__属性中; Because there is no type declaration in Python, function annotations can be used to prompt

Four, returning multiple values from a function: separating each return value with a comma "," essentially returning a tuple that can be used to return multiple values through the tuple unpacking implementation

def myfun ():   ... return 1, 2, 3>>> x, y, z = myfun ()>>> x1>>> y2& Gt;>> z3>>> a = myfun ()>>> A (1, 2, 3)

V. Define a function with default parameters

The default parameter is only bound once when the function is defined

def sample (a=x): ...   Print  >>> sample ()44>>> x = 88>>> sample ()44

The default value of the default parameter should normally be an immutable object; If you set a Mutable object, you should refer to the following way:

def Test (A, b=None): ...   if  is None:    ... = []...   Pass

Vi. let callable objects with n parameters be called with fewer arguments

That is, to give some parameters pre-bin to a fixed value, equivalent to converting to a function with a default value

def sum (A, B, C, D): ...   return A + B + C +>>> sum (1, 2, 3, 4)import  functools>>> te ST_0 = functools.partial (sum, b=2, c=3, d=4)>>> test_0 (1)10>>> test_0 (+) 109

You can also use lambda functions to implement

Lambda A, b=2, c=3, d=4: sum (A, B, C, D)>>> test_1 (1)10>>> test_1 (100 )109

Python3 from zero--{initial consciousness: 007~ function}