Reference?

[Kris Caselden]

I've searched all the Python docs I could find, but I haven't seen any
mention of referencing function arguments, such as you would with the
& in c/c++. Is this possible in Python?

[Peter Otten]

Kris Caselden wrote:

I've searched all the Python docs I could find, but I haven't seen any
mention of referencing function arguments, such as you would with the
& in c/c++. Is this possible in Python?

The analog of the Python way of handling args among the C-style languages is
Java. So, no, you are on mission impossible :-)

class Mutable:
pass

v1 = Mutable()
v1.name = "v1"
v2 = "v2" #strings are immutable

def fun(a1, a2):
a1.name = "a1"
a2 = "a2"
fun(v1, v2)

print v1.name # prints a1
print v2 # prints v2

As a workaround, you can do:

def fun2():
a1 = Mutable()
a1.name = "A1"
return a1, "A2"

v1, v2 = fun2()

print v1.name # prints A1
print v2 # prints A2

See the tutorial (http://www.python.org/doc/current/tut/node6.html) for the
tricks you *can* do with function arguments

Peter

[Peter Otten]

Kris Caselden wrote:

I've searched all the Python docs I could find, but I haven't seen any
mention of referencing function arguments, such as you would with the
& in c/c++. Is this possible in Python?

The analog of the Python way of handling args among the C-style languages is
Java. So, no, you are on mission impossible :-)

class Mutable:
pass

v1 = Mutable()
v1.name = "v1"
v2 = "v2" #strings are immutable

def fun(a1, a2):
a1.name = "a1"
a2 = "a2"
fun(v1, v2)

print v1.name # prints a1
print v2 # prints v2

As a workaround, you can do:

def fun2():
a1 = Mutable()
a1.name = "A1"
return a1, "A2"

v1, v2 = fun2()

print v1.name # prints A1
print v2 # prints A2

See the tutorial (http://www.python.org/doc/current/tut/node6.html) for the
tricks you *can* do with function arguments

Peter

[Michael Peuser]

"Kris Caselden" <go****@hanger.snowbird.net> schrieb im Newsbeitrag
news:ab**************************@posting.google.c om...

I've searched all the Python docs I could find, but I haven't seen any
mention of referencing function arguments, such as you would with the
& in c/c++. Is this possible in Python?
Your question is probably not as sophisticated: Parameter passing in Python
is *always* like & in C++.

There had been an exaustive disyussion some weeks ago: here is my
contribution:

Sent: Wednesday, August 13, 2003 9:12 AM
Subject: Re: two quick questions

The following examples might clear the more theoretical elaborations .....
def noUse(a):
a=(4,5,6)

def tricky(a):
a[0]=(7,8,9)

# case 1
x=[1,2,3]
print x
tricky(x)

x=(1,2,3)
# case 2
noUse(x)
print x

# case 3
tricky([x])
print x

# case 4
y=[x]
tricky (y)
print x
print y[0]

# case 5
tricky(x)
print x
Kindly
Michael Peuser

[Michael Peuser]

"Kris Caselden" <go****@hanger.snowbird.net> schrieb im Newsbeitrag
news:ab**************************@posting.google.c om...

I've searched all the Python docs I could find, but I haven't seen any
mention of referencing function arguments, such as you would with the
& in c/c++. Is this possible in Python?
Your question is probably not as sophisticated: Parameter passing in Python
is *always* like & in C++.

There had been an exaustive disyussion some weeks ago: here is my
contribution:

Sent: Wednesday, August 13, 2003 9:12 AM
Subject: Re: two quick questions

The following examples might clear the more theoretical elaborations .....
def noUse(a):
a=(4,5,6)

def tricky(a):
a[0]=(7,8,9)

# case 1
x=[1,2,3]
print x
tricky(x)

x=(1,2,3)
# case 2
noUse(x)
print x

# case 3
tricky([x])
print x

# case 4
y=[x]
tricky (y)
print x
print y[0]

# case 5
tricky(x)
print x
Kindly
Michael Peuser

[mackstann]

On Sat, Aug 23, 2003 at 01:57:33AM -0700, Kris Caselden wrote:

I've searched all the Python docs I could find, but I haven't seen any
mention of referencing function arguments, such as you would with the
& in c/c++. Is this possible in Python?

Python is pass-by-reference by default.

f = []
def foo(n): .... n.append("hi")
.... foo(f)
print f

['hi']

--
m a c k s t a n n mack @ incise.org http://incise.org
A bore is someone who persists in holding his own views after we have
enlightened him with ours.