一 导入模块的三种方法:
方法一:也是最常用的方法:静态导入
In [15]: import random In [16]: from random import randint |
方法二: 使用内置的__import__函数
函数介绍:这里还是推荐使用importlib.import_module()来动态导入模块的
In [17]: help( __import__) Help on built-in function __import__ in module builtins: __import__(...) __import__(name, globals=None, locals=None, fromlist=(), level=0) -> module Import a module. Because this function is meant for use by the Python interpreter and not for general use it is better to use importlib.import_module() to programmatically import a module. The globals argument is only used to determine the context; they are not modified. The locals argument is unused. The fromlist should be a list of names to emulate ``from name import ...'', or an empty list to emulate ``import name''. When importing a module from a package, note that __import__('A.B', ...) returns package A when fromlist is empty, but its submodule B when fromlist is not empty. Level is used to determine whether to perform absolute or relative imports. 0 is absolute while a positive number is the number of parent directories to search relative to the current module. |
使用方法:
In [18]: __import__("random") Out[18]: <module 'random' from 'c:\soft\python\lib\random.py'>
In [19]: __import__("django.core.files.uploadedfile") Out[19]: <module 'django' from 'c:\soft\python\lib\site-packages\django\__init__.py'>
In [20]: __import__("django.core.files.uploadedfile", fromlist=True) Out[20]: <module 'django.core.files.uploadedfile' from 'c:\soft\python\lib\site-packages\django\core\files\uploadedfile.py'> |
注意: fromlist=True参数
方法三: 使用importlib.import_module()导入
在使用之前必须先导入importlib模块:
In [23]: import importlib
In [24]: importlib.import_module("random") Out[24]: <module 'random' from 'c:\soft\python\lib\random.py'>
In [25]: importlib.import_module("django.core.files.uploadedfile") Out[25]: <module 'django.core.files.uploadedfile' from 'c:\soft\python\lib\site-packages\django\core\files\uploadedfile.py'> |
二反射:
用于反射的4个内置函数getattr、hasattr、setattr、delattr
综合上上述的动态导入使用:
In [1]: m=__import__("random") In [2]: hasattr(m,"randint") Out[2]: True In [3]: getattr(m,"randint") Out[3]: <bound method Random.randint of <random.Random object at 0x000001DF4C18A9C8>> In [7]: getattr(m,"randint")(1,20) Out[7]: 9 In [8]: setattr(m,"name","ywhyme") In [10]: m.name Out[10]: 'ywhyme' In [11]: delattr(m,"name") In [12]: m.name --------------------------------------------------------------------------- AttributeError Traceback (most recent call last) <ipython-input-12-0634a6ce99cb> in <module>() ----> 1 m.name AttributeError: module 'random' has no attribute 'name' |
除此之外还可以用于现有对象进行反射