函数定义
__import__(name, globals={}, locals={}, fromlist=[], level=-1) -> 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. -1 is the original strategy of attempting
both absolute and relative imports, 0 is absolute, a positive number
is the number of parent directories to search relative to the current module. name:引用模块名称，如‘sys’, ‘libs/module.a‘
fromlist:子模块列表，如果name是a.b的格式，则必须把b加入fromlist中
用途
- 动态导入模块
例子
import os
def test():
datetime = __import__(‘datetime‘)
print datetime.datetime.now()
a = __import__("module.module_a", globals={}, locals={}, fromlist=["module_a"], level=-1)
print a.sub(x, y)
test()调用不同目录的模块
- 应该先sys.path.append(模块所在路径)，然后再用相对路径引用
例：
在下面这个例子中，由于celery调用，运行路径跟当前路径不同，直接引用module.module_a会报错：无法找到该模块，同时如果__import__的第一个参数用绝对路径，会报错：不可使用文件名引用
正确方法就是先在系统路径中加入当前路径，然后用相对路径引用
from celery import Celery
import os
import sys
current_path = os.path.dirname(os.path.realpath(__file__))
sys.path.append(current_path)
app = Celery(‘tasks‘, backend=‘amqp‘, broker=‘amqp://test:[email protected]/testhost‘)
@app.task
def add(x, y):
a = __import__("module.module_a", globals={}, locals={}, fromlist=["module_a"], level=-1)
print a.add(x, y)