#练习：未使用共享变量

from multiprocessing import Process

def f(n, a):

    n = 3.1415927

    for i in range(len(a)):

        a[i] = -a[i]

if __name__ == '__main__':

    num = 0

    arr = range(10)

    p = Process(target = f, args = (num, arr))

    p.start()

    p.join()

    print num

    print arr[:]

#练习：进程间共享变量，进程间都操作了num这个共享变量

from multiprocessing import Process,Value,Array

def f(n,a):

    n.value=3.1415

    for i in range(len(a)):

        a[i]=-a[i]

if __name__=="__main__":

    num.value=Value("d",0.0)    # 创建一个进程间共享的数字类型，默认值为0,d表示小数

    array=Array("i",range(10))  # 创建一个进程间共享的数组类型，初始值为range[10]，i表示整数

    p=Process(target=f,args=(num,array))

    p.start()

    p.join()

print num.value

print array[:]

#练习：共享string类型变量

from multiprocessing import Process,Manager,Value

from ctypes import c_char_p

def greet(str):

    str.value=str.value+",wangjing"

if __name__=="__main__":

    manager=Manager()  #多进程可以共享的命名空间

    shareStr=manager.Value(c_char_p,"hello")   #这里c_char_p是个类

    p=Process(target=greet,args=(shareStr,))

    p.start()

    p.join()

    print shareStr.value

#练习:创建共享的字典类型，列表类型

from multiprocessing import Process, Manager

def f( shareDict, shareList ):

    shareDict[1] = ''

    shareDict[''] = 2

    shareDict[0.25] = None

    shareList.reverse() # 翻转列表

if __name__ == '__main__':

    manager = Manager()

    shareDict = manager.dict() # 创建共享的字典类型

    shareList = manager.list( range( 10 ) ) # 创建共享的列表类型

    p = Process( target = f, args = ( shareDict, shareList ) )

    p.start()

    p.join()

    print shareDict

    print shareList