qgis - How to get User and Password of a PostGIS layer from PyQGIS

I wonder if it is possible to get the user and password for a PostGIS database if they are stored in the PostGis connection information.

I get the connection information at the moment from the active layer like this:

connInfo = QgsDataSourceURI(layer.dataProvider().dataSourceUri()).connectionInfo()

print connInfo
dbname='test_geodata_project' host=10.0.4.111 port=5432 sslmode=disable

userInfo = QgsCredentials.instance().get(connInfo, None, None)
print userInfo
(True, u'testuser', 'test')

But the user has to type in the user/password manually. Is there something like the connectionInfo() but with user/password?

Answer

Yes, you can do that, but only if you chose to save user and password while establishing the PostGIS connection.

If you did so and your active layer is a PostGIS layer, you can access the connection information this way:

layer = iface.activeLayer()
source = layer.source()
print source

You'll get a key-value string like this:

dbname='mydb' host=localhost port=5432 user='myuser' password='mypassword' sslmode=disable key='gid' srid=4326 type=MULTIPOLYGON table="public"."mytable" (geographicextent) sql=

From which you can obtain the password this way:

kvp = source.split(" ")
for kv in kvp:
    if kv.startswith("password"):
        thePassword = kv.split("=")[1][1:-1]
        print thePassword

Include a similar if for the user into the for loop and you are done.