urllib with x509 certs

[Lacrima]

Hello!

I am trying to use urllib to fetch some internet resources, using my
client x509 certificate.
I have divided my .p12 file into mykey.key and mycert.cer files.
Then I use following approach:
>>> import urllib
>>> url = 'https://example.com'
>>> xml = '''<request>
... <somexml>somexml</somexml>
</request>'''
>>> opener = urllib.URLopener(key_file = 'mykey.key', cert_file = 'mycert.cer')
>>> f = opener.open(url, xml)

This works Ok! But every time I am asked to enter PEM pass phrase,
which I specified during dividing my .p12 file.
So my question... What should I do to make my code fetch any url
automatically (without asking me every time to enter pass phrase)?
As I understand there is impossible to specify pass phrase while
constructing URLopener.
So what should I do?

With regards, Max
(sorry if my English isn't very proper)