1+ #函数除了正常定义的必选参数外，还可以使用默认参数、可变参数和关键字参数，
2+
3+
4+ #x2
5+ def power1 (x ):
6+ return x * x
7+
8+
9+ #x3 x4 x5
10+ def power2 (x , n ):
11+ s = 1
12+ while n > 0 :
13+ n = n - 1
14+ s = s * x
15+ return s
16+
17+
18+ power2 (5 , 2 ) #25
19+
20+ #默认参数 n是默认参数
21+
22+
23+ def power3 (x , n = 2 ):
24+ s = 1
25+ while n > 0 :
26+ n = n - 1
27+ s = s * x
28+ return s
29+
30+
31+ power3 (5 ) #25
32+ power3 (5 , 2 ) #25
33+
34+ #可变参数
35+
36+
37+ # a2 + b2 +c2
38+ def calc (* numbers ):
39+ sum = 0
40+ for num in numbers :
41+ sum = sum + num * num
42+ return sum
43+
44+
45+ #calc 可以传入任意个参数
46+ calc (1 , 2 , 3 , 4 ) #30
47+ calc (1 , 2 ) #5
48+ calc () # 0
49+
50+ #传入一个list或tuple 在list或tuple前面加一个*号,把list或tuple的元素变成可变参数传进去
51+ nums = [1 , 2 , 3 , 4 ]
52+ calc (* nums ) #30
53+
54+ #关键字参数
55+ #可变参数允许你传入0个或任意个参数，这些可变参数在函数调用时自动组装为一个tuple。而关键字参数允许你传入0个或任意个含参数名的参数，这些关键字参数在函数内部自动组装为一个dict。
56+
57+
58+ #函数person除了必选参数name和age外，还接受关键字参数kw。在调用该函数时，可以只传入必选参数：
59+ def person (name , age , ** kw ):
60+ print ('name:' , name , 'age:' , age , 'other:' , kw )
61+
62+
63+ person ('colin' , 90 ) #name: colin age: 90 other: {}
64+
65+ #也可以传入任意个数的关键字参数
66+ person (
67+ 'Bob' , 35 , city = 'Beijing' ) #name: Bob age: 35 other: {'city': 'Beijing'}
68+
69+ person (
70+ 'Adam' , 45 , gender = 'M' , job = 'Engineer'
71+ ) #name: Adam age: 45 other: {'gender': 'M', 'job': 'Engineer'}
72+
73+ #先组装出一个dict,把该dict转换为关键字参数传进去
74+ extra = {'city' : 'Beijing' , 'job' : 'Engineer' }
75+ person (
76+ 'Jack' , 24 ,
77+ ** extra ) #name: Jack age: 24 other: {'city': 'Beijing', 'job': 'Engineer'}
78+
79+ #命名关键字参数
80+ #限制关键字参数的名字 和关键字参数**kw不同，命名关键字参数需要一个特殊分隔符*，*后面的参数被视为命名关键字参数。
81+
82+
83+ def person1 (name , age , * , city , job ):
84+ print (name , age , city , job )
85+
86+
87+ person1 ('Jack' , 24 , city = 'Beijing' , job = 'Engineer' ) #Jack 24 Beijing Engineer
88+
89+ #如果函数定义中已经有了一个可变参数，后面跟着的命名关键字参数就不再需要一个特殊分隔符*了：
90+
91+
92+ def person2 (name , age , * args , city , job ):
93+ print (name , age , args , city , job )
94+
95+
96+ def print_scores (** kw ):
97+ print (' Name Score' )
98+ print ('------------------' )
99+ for name , score in kw .items ():
100+ print ('%10s %d' % (name , score ))
101+ print ()
102+
103+
104+ stu = {'Ame' : 20 , 'Pbe' : 30 , 'ESE' : 90 }
105+ print_scores (** stu )
106+
107+ #
108+ # Name Score
109+ #------------------
110+ # Ame 20
111+ # Pbe 30
112+ # ESE 90
113+
114+
115+ def print_info (name , * , gender , city = 'Beijing' , age ):
116+ print ('Personal Info' )
117+ print ('---------------' )
118+ print (' Name: %s' % name )
119+ print (' Gender: %s' % gender )
120+ print (' City: %s' % city )
121+ print (' Age: %s' % age )
122+ print ()
123+
124+
125+ print_info ('Bob' , gender = 'male' , age = 20 )
126+
127+ #Personal Info
128+ #---------------
129+ # Name: Bob
130+ # Gender: male
131+ # City: Beijing
132+ # Age: 20
133+
134+ print_info ('Lisa' , gender = 'female' , city = 'Shanghai' , age = 18 )
135+
136+ #Personal Info
137+ #---------------
138+ # Name: Lisa
139+ # Gender: female
140+ # City: Shanghai
141+ # Age: 18
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