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__(&＃39;string&＃39;)

2. 使用imp 模块

import imp 
stringmodule = imp.load_module(&＃39;string&＃39;,*imp.find_module(&＃39;string&＃39;))
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,&＃39;t&＃39;)
2. &＃39;var&＃39; in locals().keys()
3. &＃39;var&＃39; in dir()
4. vars().has_key(&＃39;s&＃39;)

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(&＃39;Obj&＃39;,(),{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__ == &＃39;__main__&＃39;:
  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 &＃39;class!!!&＃39;

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(&＃39;util.common&＃39;,[&＃39;*&＃39;])
ins=dyn.getClassInstance(&＃39;C&＃39;,&＃39;gao&＃39;)
dyn.execMethod(ins,&＃39;test&＃39;)
dyn.execfunc(&＃39;test&＃39;,&＃39;Hello&＃39;,&＃39;function!&＃39;)

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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