Python全局未在新对象实例中更新

Question

我有一个带有全局var的Python文件，并定义了一个类：

ROOT = 'https://api.example.com/2.0/'
class Mail(object):
    def __init__(self, api_key):
        self.name = "FName"
        if api_key.find('-'):
            dc = api_key.split('-')[1]
        global ROOT
        print "initing root to: %s" % (ROOT,)
        ROOT = ROOT.replace('https://api.', 'https://'+dc+'.api.')
        print "initing after replace of ROOT: %s" % (ROOT,)
    def pprint(self):
        print 'POST to %s' % (ROOT,)

ROOT全局设置后似乎不会更新：

>>> import pyglob 
>>> mc = pyglob.Mail('dfadsfad-us1')
initing root to: https://api.example.com/2.0/
initing after replace of ROOT: https://us1.api.example.com/2.0/
>>> mc.pprint()
POST to https://us1.api.example.com/2.0/
>>> mc3 = pyglob.Mail('dfadsfad-us3')
initing root to: https://us1.api.example.com/2.0/
initing after replace of ROOT: https://us1.api.example.com/2.0/
>>> mc3.pprint()
POST to https://us1.api.example.com/2.0/
>>> mc.pprint()
POST to https://us1.api.example.com/2.0/

有人能解释一下这种情况是如何发生的以及为什么会发生吗？

Answer 1

制作完ROOT = https://us1.api.example.com/2.0/后，ROOT.replace('https://api.', 'https://'+dc+'.api.')什么都不做，因为'https://api.'已不在ROOT中--您已经替换了它。

整个情况看起来非常混乱，您可能想要重构它，而不是重新绑定全局。