Python基础篇(六)
retun空值，后面的语句将不再被执行
>>> def test():
... print("just a test!")
... return
... print("will not be print")
...
>>> test()
just a test!
和Java类似，在传递参数时，当参数是字符串，元组时，传递的其实是拷贝，修改实际参数不会影响到形式参数。当参数是对象时，修改实际参数将会影响到形式参数。
>>> def changeName(name):
... name = "Changed Name"
... return name
...
>>> name = "Jhon Brown"
>>> changeName(name)
'Changed Name'
>>> name
'Jhon Brown'
实参为对象时的情况：
>>> def changeList(list):
... list[0] = "Change Element"
... return list
...
>>> list = ["one","two"]
>>> changeList(list)
['Change Element', 'two']
>>> list
['Change Element', 'two']
可以为实参取别名，这样当参数为多个的时候不会因位置错误而导致错误的结果
>>> def hello1(arg1,arg2):
... print("%s %s" % (arg1,arg2))
...
>>> hello1(arg1 = "hello",arg2 = "world")
hello world
使用*收集剩余的参数：
>>> def printParams(title,*params):
... print(title)
... print(params)
...
>>> printParams("Params",2,3,4)
Params
(2, 3, 4)
定义和调用函数时都是用**，适用于元组或者字典。
>>> def with_stars(**database):
... print(database["name"]+ "\'s age is" + database["age"])
...
>>> database = {"name":"Grubby","age":"29"}
>>> with_stars(**database)
Grubby's age is29
>>> def without_stars(database):
... print(database["name"]+ "\'s age is" + database["age"])
...
>>> data = {"name":"Grubby","age":"29"}
>>> without_stars(data)
Grubby's age is29
>>> def story(kwd):
... print("Once there is a %(player)s called %(name)s," % kwd)
...
>>> kwd = {"player":"king","name":"Chrile"}
>>> story(kwd)
Once there is a king called Chrile,
vars函数会返回一个字典，包含变量与赋值的关系
>>> x,y,z =1,2,3
>>> scope =vars()
>>> scope["x"]
1
递归调用的例子
def search(sequence,number,low=0,upper = None):
if upper is None :
upper = len(sequence) -1
if low == upper:
if sequence[low] == number:
return low
else:
return -1
else:
index = (int)((low + upper)/2)
if sequence[index] > number:
return search(sequence,number,low,index-1) #这里的return是必须的，否则将没有返回值
elif sequence[index] < number:
return search(sequence,number,index+1,upper)
else:
return index
sequence = [1,3,9,11,56]
search(sequence,3)
创建自己的类：
>>> class Person:
... def setName(self,name):
... self.name = name
... def getName(self):
... return self.name
... def greet(self):
... print("name is %s" % self.name)
...
>>> foo = Person()
>>> bar = Person()
>>> foo.setName("Luke")
>>> foo.getName()
'Luke'
>>> foo.greet()
name is Luke
>>> bar.setName("Sky")
>>> bar.getName()
Sky'
>>> bar.greet()
name is Sky
>>> bar.name
'Sky'
>>> bar.name = "Jason" #属性使用类加上.直接使用
>>> bar.greet()
name is Jason
>>> class Bird:
... __song = "spark"
... def sing(self):
... print(self.song)
...
>>> bird = Bird()
>>> bird.sing()
Traceback (most recent call last):
File "
File "
AttributeError: 'Bird' object has no attribute 'song'
>>> class Bird:
... song = "spark"
... def sing(self):
... print(self.song)
...
>>> bird = Bird()
>>> bird.sing()
spark
