Question about expression evaluation

[Scott Gould]

Hi folks,

This is a head-scratcher to me. I occasionally get this error:

---
  File "/var/www/myproj/account/views.py", line 54, in account
    if request.account.is_instructor and request.account.contact and
request.account.contact.relationship.institution_party_number:

AttributeError: 'NoneType' object has no attribute 'relationship'
---

I'm leaving out all the supporting code deliberately. My question is
simple: if python short-circuits evaluation and
"request.account.contact" is None, how is it even getting as far as
"request.account.contact.relationship.institution_party_number"?

Thanks!