函数初探

函数的定义.返回值.参数
#len()

s = "jinlaoban"

#len()

# i = 0
# for k in s:
#     i += 1
# print(i)

# s1 = "ahdsajks"
#
# i = 0
# for k in s1:
#     i += 1
# print(i)
s = "jinlaoban"

# def my_len(): #personal function
#     i = 0
#     for k in s:
#         i += 1
#     # print(i)
#     return i #return
#
# length = my_len()
# print(length)
#function
# define function ,you can use in anywhere
#no return just only print


#the importance of return
#a,b
#len(a)  #inner function
#len(b)
# the function define and transfer is not  porcess

#Return .the return has three situation
#1.no return    no return , just return :end the function, return None
# 2.return only one results
#it can return any types
# if return it can accept
# it will stop while meet the return
# 3.return many results
# many results matching  the return
#only one variable can accept as turple

# def func():
#     l = ["jinlaoban", "erge"]
#     for i in l:
#         print(i)
#         if i == "jinlaoban":
#             return i
#     #  return
#     # print("ergeerge")
#
# ret = func()
# print(ret)

# def func():
#
#     return {"k":"v"}
#     return 1
#
# print(func())

#Return many results
# def func2():
#     return 1, 2, 3
#
# r1 = func2()
#
# print(r1)

# s = "jinlaoban"
# def my_len(s):  #personal function  s------>resembling parameter(形式参数)
#     i = 0
#     for k in s:
#         i += 1
#     # print(i)
#     return i
#
# s = "jinlaoban"
# ret = my_len(s)          #actual parameter(实际参数)
# print(ret)
# ret = my_len([1,2,3,4,5])
# print(ret)
# my_len(ret) #deliver parameter

# def f1(l1):
#     for i in l1:
#         print(i)
#
# def f2(l1):
#     f1(l1)
#     for i in l1:
#         print(i)
#
# f2([1,2,3])
# f1([1,2,3,4])
# f2([1,2,3,4])

#parameter
#  no parameter-------->the define function and the transter function is just no things
# one parameter ------->transter something is something
# many parameters------->1.positions parameter 2.keywords transfer 3. mixture

# def my_sum(a, b):
#     res = a + b
#     return res
#
# ret = my_sum(b = 1,a = 2)
#
# print(ret)

# def classmate(name, sex):
#     print("{} : {}" .format(name, sex))
#
# classmate("jinliaoyuan", "boy")

#use the default settings:

# def classmate(name, sex ="boy"):
#     print("{} : {}" .format(name, sex))

# classmate("jinliaoyuan")
# classmate("zhangjiahui", "girl")

#Have problems

# def sum(a, b , c=0,):
#     pass
#
# sum(1,2)
# sum(1,2,3)
# sum(1,2,3,4)
#dynamic parameter
# def sum(*args):
#     n = 0
#     for i in args:
#         n += i
#     return n
#
# sum(1,2)
# sum(1,2,3)
# sum(1,2,3,4)

# parameter sequence 1.positional parameter 2.dynamic parameter(*agrs), 3.default parameter

#problems  transfer many dafault parameter -->turple

# def func(*agrs, l =[]):
#     print(agrs, l)
#
#
# func(1,2,3, ["lat", 1])
# func(1,2,3,l = [1,2])

# #**kwargs --------->dic

# def func(**kwargs):
#     print(kwargs)
#
# func(a=1,b=2, c=3)
# func(a=1, b =2)
# func(a=1)
# advantage : it can accept many parameter

# def func(*args, **kwargs):
#     print(args,kwargs)
#
# func(1,2,3,4,5, a= "aaa", b = "bbb")
#position parameter, *args, "default parameter , **kwargs,
# def func(*args, default = 2, **kwargs):
#     print()

#dynamic parameter have another methed

# def func(*args):    #站在形参的角度上,给变量加上*,就是组合所有打散的值
#     print(args)
#
# func(1,2,3,4)
# l = [1,2,3,4,5]
# # func(l[1],l[2],l[3])
# func(*l)    #站在实参的角度上,给序号加上*,就是将这个序列按照顺序打散

# def func(**kwargs):
#     print(kwargs)
# 
# func(a=1,b=2)
# d = {"a":"1", "b":"2"}
# func(**d)

#函数注释
# def func():
#     ''' 这个函数实现了什么功能
#     参数1,
#     参数2:
#     :return ,
#     '''
#     pass

#默认参数的陷阱
#1.函数的定义 def
#2.函数的调用
#3.函数的返回值  return
#返回一个值,返回多个值可以用多个变量接收,也可以用一个变量接收
#函数的参数  形参和实参(按照位置传参,按照关键字传参,先按照位置,在按照关键字)
    #形参:
        #位置参数
        #*args 可以接收任意多个位置参数
        #默认参数  可以传可以不传
        #**Kwargs:可以接收多个关键字参数

函数:
　　内置函数

　　自定义函数