Python global not updating in new object instance

Question

I have a Python file with a global var and define a class:

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,)

It seems that the ROOT global is not updated once it's set:

>>> 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/

Can someone explain how this works and why it happens?

Because after the first replace call there's no 'https://api.' to replace. — Ashwini Chaudhary
– Ashwini Chaudhary, Commented Sep 7, 2014 at 23:09

Mike Graham · Accepted Answer · 2014-09-07 23:11:22Z

1

After you've made ROOT = https://us1.api.example.com/2.0/, ROOT.replace('https://api.', 'https://'+dc+'.api.') doesn't do anything, since 'https://api.' is no longer in ROOT--you've replaced it.

This whole situation looks extremely messy and you probably want to refactor this not to rebind globals at all.

answered Sep 7, 2014 at 23:11

Mike Graham

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2 Comments

Gezim Over a year ago

Cool. But it's safe to say that even if the replace is fixed, sharing a global var could cause conflicts when there's more than one instance of the class, right?

Mike Graham Over a year ago

Yes. If you want something for the instance, make it an attribute of self.

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