Python函数参数传递方法四种(位置、关键字、默认值、包裹位置

位置传递

#--coding:utf-8-- 
def send(name,address):
    return 'package is sent to %s, located in %s' %(name, address)
print(send('winnie','shanghai'))

关键字传递

def run(name,length, date):
    return '%s ran %s on %s' %(name,length,date)
#关键字传递时，可以无视参数顺序，名字对了就行。
print(run(length = '5km',date ='11/29/2016',name = 'winnie'))
#关键字和位置混用，但要注意位置参数要出现在关键字前面。 如果不，那编译器不知道除了几个有名字的，位置的顺序。
print(run('winnie',length = '5km',date ='11/29/2016'))

输出结果：
winnie ran 5km on 11/29/2016
winnie ran 5km on 11/29/2016
[Finished in 0.2s]

默认值参数

# 3. 默认值参数： 可以给出参数默认值
# 我们跑团每周二的例行约跑
def runWeekly(name,length, time = 'Tuesday 5：00PM'):
    return '%s ran %s on %s' %(name,length,time)

调用：

print(runWeekly('jin','5km'))
print(runWeekly('jin','5km','Wednesday'))
print(runWeekly('jin',time = '5km','Wednesday')) #Error


  File "C:\pytest\Sele\tem1111.py", line 20
    print(runWeekly('jin',time = '5km','Wednesday'))
SyntaxError: non-keyword arg after keyword arg
[Finished in 0.2s with exit code 1]

包裹传递

# 4. 包裹传递 （*/**）
# 参数被 collect收集，type： tuple
def subselect(*collect):
    print collect
    print type(collect)
# 参数被 aa收集，type： dict
def packing(**aa):
    #print test
    print type(aa)
    print aa

调用：

subselect(['ppe-test-1','dddd'])
packing(a=1,b=2,sub=[11,22])

输出：

<type 'tuple'>
<type 'dict'>
{'a': 1, 'b': 2, 'sub': [11, 22]}
[Finished in 0.2s]

解包

# 5.Unpacking with */** 
tuple1 = ['test1','test2','test3']
dictionary1 = {'at':'88wi','b':'secondParam','third':'winnie'}
print('dictionary1 ', dictionary1)
def useDict(at,b,third):
    print (at , b ,third)
useDict(**dictionary1)  #把字典参数解包 此时相当于关键字参数传递 名字和函数定义的参数名必须要一一对应
useDict(*tuple1)    #把元组解包 此时相当于位置参数传递