On 5/5/2014 8:39 PM, Satish Muthali wrote:
Hello experts,
I have a burning question on how to pass variable by reference in
Python.
Python passes objects to functions. CPython implements this by passing
object pointers. In one sense, your request is impossible. In another,
it already happens.
I understand that the data type has to be mutable.
In C, all data are mutable, so copying a block of memory versus passing
a pointer is the meaningful distinction. In Python, mutable arguments
can be mutated and immutable args cannot, so *that* is the only
meaningful distinction. Strings are not mutable.
For example, here’s the issue I am running in to:
I am trying to extract the PostgreSQL DB version for example:
/pgVer = [s.split() for s in os.popen("psql
--version").read().splitlines()]/
/ print pgVer[0]/
/ for i, var in enumerate(pgVer[0]):/
/ if i == len(pgVer[0]) - 1:/
/ pgversion = var/
/
/
I would now like to pass ‘pgversion’ (where the value of pgversion is
9.3.4) by reference, for example:
I want to nuke /var/lib/postgresql/9.3.4/main/data , however
programatically I want it to be as: /var/lib/postgresql/*/<value of
pgversion>/*/main/data
It is not clear whether you want to delete a file or rename it. Either
is easy and neither depend on passing mechanism.
--
Terry Jan Reedy
--
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