The P4 Handshake

  I recently ran into the issue at work where we had to make sure perforce and maya were communicating when a new file was exported to the tree.  This was only an issue on newer projects due to a new pipeline with a new engine choice.   We were already using the P4 python library  in house,  but we just needed to make sure the right functions were called, users were logged in, etc.  I just wanted to post a few findings because I felt like the documentation was particularly clear for what I needed.

Example Scenario:
  On export of a new asset to the P4 tree, I wanted to add the new file to the P4 Depot.  If a user already logged into P4, then a ticket exists ( lasts for 12 hours by default in P4 ).  If a user has not logged into Perforce, then prompt the user for the info and create a ticket using the perforce python api run_login() call.

Now the important piece of info that documentation was not clear about: you can call "add" or "edit" calls from P4Python as long as a ticket exists and hasn't expired on the matching user/port/client info.  The documentation seems to infer you can pass an argument into run_login() of the ticket hash id, but according to perforce support it is worded incorrectly.  So we set out to check if the user had an existing non-expired ticket by using this call..

from P4 import P4 as p4api
mP4 = p4api()

mP4.port = sP4Server
mP4.user = sP4User
mP4.client = sP4Workspace
mP4.host = os.environ["COMPUTERNAME"].upper()

bConnection = mP4.connect()

try:
    mP4.fetch_change()

    mP4.disconnect()
except:
    # prompt user for password, because fetch change failed

The try/except, using fetch_change() gave me a quick way to check if the current info for the user was correct for an active and existing ticket without actually doing any work in p4 ( such as edit/add ).  If the fetch_change() failed, I proceeded with some user prompting to supply correct information.

If it was successful, I later would just call the edit or in this case the "add" perforce python api call..

mP4.run( "add", sPathToFile )

  These are just a few snippets of the fix we had to implement to make sure we are correctly adding to changelists and interacting with P4.  Maybe not knowing you can just call edit/add if you have a ticket isn't an issue for other TAs but it was one of those things that really bothered me when I got into it and it felt the need to post about it.