使用变量"interpolation"创建导入语句. [英] Create an import statement using variable "interpolation"

问题描述

我有一长串可能需要导入的文件.我将只需要其中的1个，它们都具有相同的界面. (选择付款网关处理付款)

I have a long list of possible files I need to import. I will only ever need 1 of them and they all have the same interface. (Choosing a payment gateway to process a payment)

假设我有一个字典，代表所有网关文件的名称.

Suppose I have a dictionary that represents the name of all the gateway files.

即

gateways = {
   '1' : 'authorize',
   '2' : 'paysimple',
   '3' : 'braintreepayments',
   '4' : 'etc',
}

基于数据库中的信息，我知道该词典的关键字.因此，如果我收到网关值为1的付款过程请求，我知道它需要由Authorize.net处理. 2将由简单付款"处理.等等.

I know the keys to this dictionary based on information from a database. So, if I receive a payment process request with a gateway value of 1 I know it needs to be handled by Authorize.net. A 2 is to be processed by Pay Simple. Etc.

我希望能够创建一个导入语句，该导入语句是用我所知道的信息构建的，而不是一个可怕的elif语句列表.

I'd like to be able to create an import statement that is built with the information I know rather than a horrible list of elif statements.

考虑以下简单方法:

# For the purposes of this example assume payment_gateway is defined
# elsewhere and represents the key to the dictionary
gateway_file = gateways.get(payment_gateway)

import_str = "from gateway_interface.%s import process" % gateway_file
gogo(import_str)

gogo是导致import语句实际导入的一种方式.

Where gogo is a way to cause the import statement to actually import.

这有可能吗?

推荐答案

最简单

process = __import__('gateway_interface.'+gateway_file,fromlist=['foo']).process

编辑:只要fromlist不是空列表，fromlist中的'foo'可以是任何东西. 为什么Python的__import__需要fromlist?解释了一点奇怪.

EDIT: 'foo' in the fromlist can be anything, as long as fromlist is not an emptylist. That little bit of strangeness is explained in Why does Python's __import__ require fromlist?.

我还必须进行编辑，因为在我的第一篇文章__import__中，它没有按预期工作，如

I also had to edit because in my first post __import__ didn't work as expected as further described in Python's __import__ doesn't work as expected.

如果您使用的是python 2.7

if you have python 2.7

import importlib
process = importlib.import_module('gateway_interface.'+gateway_file).process

WAAAAY很酷，那就是使用package_tools(例如from pkg_resources import iter_entry_points)

WAAAAY cool would be to use package_tools (e.g. from pkg_resources import iter_entry_points)

这可以为您提供一种找到正确功能的解决方案，即使它们是位于gateway_interface之下的奇特软件包中也是如此.如果它们都集中在一个地方，而您又不需要过分的控制点，那么...是的，只是__import__

That could give you a solution to find the right function even if they are in odd packages not under gateway_interface. If they are all on one place and you don't need the sytle-point that is overkill so ... yeah just __import__

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