python动态加载包的方法详细介绍

动态加载模块有三种方法

1. 使用系统函数__import_()

stringmodule = __import__('string')

2. 使用imp 模块

import imp 
stringmodule = imp.load_module('string',*imp.find_module('string'))
imp.load_source("TYACMgrHandler_"+app.upper(), filepath)

3. 用exec

import_string = "import string as stringmodule"
exec import_string

变量是否存在

1. hasattr(Test,'t')
2. 'var' in locals().keys()
3. 'var' in dir()
4. vars().has_key('s')

动态增加属性

class Obj(object):
 pass
def main():
 list=["a","b", "c"]
 for i inrange(1,len(list),2):
 Obj = type('Obj',(),{list[i]:lambdaself,s:obj.__setattr__(s.split(" = ")[0],s.split(" = ")[1])})
 obj =Obj()
 for i inrange(0,len(list),2):
 obj.__setattr__(list[i],list[i]) 
 obj.a =1
 obj.b("a =2")
 obj.b("c =3")
 printobj.a
 printobj.c
if __name__ == '__main__':
 main()

动态载入包：

def test(s,e):
 print s
 print e
class C():
 def __init__(self,name):
 print name
 def test(self):
 print 'class!!!'

加载器代码：

class Dynload():
 def __init__(self,package,imp_list):
 self.package=package
 self.imp=imp_list
 def getobject(self):
 return __import__(self.package,globals(),locals(),self.imp,-1)
 def getClassInstance(self,classstr,*args):
 return getattr(self.getobject(),classstr)(*args) 
 def execfunc(self,method,*args):
 return getattr(self.getobject(),method)(*args)
 def execMethod(self,instance,method,*args):
 return getattr(instance,method)(*args)
#Test:
dyn=Dynload('util.common',['*'])
ins=dyn.getClassInstance('C','gao')
dyn.execMethod(ins,'test')
dyn.execfunc('test','Hello','function!')

根据名字加载指定文件

def loadapp(self, app):
 filepath="mgr/"+app+".py"
 if os.path.exists(filepath):
 imp.load_source("TYACMgrHandler_"+app.upper(), filepath)
//修改了app.py，从新调用这个函数，新的代码自动生效

根据名字调用对应方法

return getattr(self, op)(args.get("port"), args) //op="start" args=dict
getattr(self, self.request.method.lower())(*args, **kwargs)

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