Printing variable names

[Mike]

mylist = [a, b, c]

I want to print out the names of the variables in mylist (not the
values of a, b, and c). How do I go about doing this. Thanks.

Mike

[Mark McEahern]

Mike wrote:

mylist = [a, b, c]

I want to print out the names of the variables in mylist (not the
values of a, b, and c). How do I go about doing this. Thanks.

Mike

There's no simple answer to this. Consider the fact that you can have
more than one name bound to any given mutable instance. What if:

a = range(10)
b = a

mylist = [a]

what name do you want printed for the first item in mylist--'a' or 'b'?

One idea is to use a dictionary instead. Then:

for key, value in mydict.iteritems():
print '%(key)s = %(value)s' % locals()

I'm curious what problem you're trying to solve.

Cheers,

// m

[Nuff Said]

On Sun, 18 Jan 2004 11:22:08 -0800, Mike wrote:

mylist = [a, b, c]

I want to print out the names of the variables in mylist (not the
values of a, b, and c). How do I go about doing this. Thanks.

The following example shows that this does not really make sense:

a = 1; b = 2; c = 3;
mylist = [a, b, c]
a = 4; b = 5; c = 6;
print mylist
print a, b, c

Result:
[1, 2, 3]
4 5 6

and *not*:
[4, 5, 6]
4 5 6

You might want to google for 'Python object reference' etc.
Moreover, having a look (e.g. in the tutorial) at how Python
passes arguments to functions (mutable and immutable objects)
might help to get a better understanding of what is going on
behind the scenes.

HTH / Nuff

[Dan Bishop]

Mark McEahern <ma**@mceahern.com> wrote in message news:<ma**************************************@pyt hon.org>...

Mike wrote:

mylist = [a, b, c]

I want to print out the names of the variables in mylist (not the
values of a, b, and c). How do I go about doing this. Thanks.
There's no simple answer to this. Consider the fact that you can have
more than one name bound to any given mutable instance.

Why did you specify "mutable"? The same applies to immutable
instances.
I'm curious what problem you're trying to solve.

So am I. The question shows up here all the time, but I've never seen
a reason for it.

[Scott David Daniels]

Mark McEahern wrote:

Mike wrote:

mylist = [a, b, c]

I want to print out the names of the variables in mylist (not the
values of a, b, and c). How do I go about doing this. Thanks.
Mike

... One idea is to use a dictionary instead. Then:
for key, value in mydict.iteritems():
print '%(key)s = %(value)s' % locals()
I'm curious what problem you're trying to solve.

Mark's questions are very much on target. If the purpose is debugging,
you might be satisfied with something like:

def vnames(value, *dicts):
"""From a value and some dictionaries and give names for the
value"""
result = []
for d in dicts:
result.extend([key for key, val in d.iteritems()
if val is value])
result.append(repr(value))
return result

Which you might use like:

a,b,c = 1,2,3
d,e,f = 5,4,3

for v in range(10):
print v, vnames(v, locals(), globals())

Note: You probably need only locals or globals if you are at the top
level of an interpreter such as Idle or the python shell.
You might prefer '==' to 'is', but remember that 0.0 == 0 == 0L.

-Scott David Daniels
Sc***********@Acm.Org

[Mike]

Thanks for the info. That does clear up a few things for me.

This is what I'm trying to accomplish:

Basically I have a list of pointers to functions (or whaterver it's called in
Python). Something like this:

commands = [func1, func2, ...funcN]

This is in a script that I use to test an embedded system through the comport.
I call the script with the command number (func1 etc...), which calls the
corresponding function, which sends a command to the embedded system.

I'd like to be able to call the script with --help and have it spit out
the list of commands (the names func1, func2 etc...).
Mike


Mark McEahern <ma**@mceahern.com> wrote in message news:<ma**************************************@pyt hon.org>...

Mike wrote:

mylist = [a, b, c]

I want to print out the names of the variables in mylist (not the
values of a, b, and c). How do I go about doing this. Thanks.

Mike

There's no simple answer to this. Consider the fact that you can have
more than one name bound to any given mutable instance. What if:

a = range(10)
b = a

mylist = [a]

what name do you want printed for the first item in mylist--'a' or 'b'?

One idea is to use a dictionary instead. Then:

for key, value in mydict.iteritems():
print '%(key)s = %(value)s' % locals()

I'm curious what problem you're trying to solve.

Cheers,

// m

[Peter Otten]

Mike wrote:

This is what I'm trying to accomplish:

Basically I have a list of pointers to functions (or whaterver it's called
in
Python). Something like this:

commands = [func1, func2, ...funcN]

This is in a script that I use to test an embedded system through the
comport. I call the script with the command number (func1 etc...), which
calls the corresponding function, which sends a command to the embedded
system.

I'd like to be able to call the script with --help and have it spit out
the list of commands (the names func1, func2 etc...).

You're lucky, functions "know" their name:

def func1(): pass .... def func2(): pass .... for f in [func1, func2]:

.... print f.__name__
....
func1
func2

Peter

[Mark McEahern]

[Me]

There's no simple answer to this. Consider the fact that you can have
more than one name bound to any given mutable instance.
[Dan Bishop] Why did you specify "mutable"? The same applies to immutable
instances.

I didn't think through the immutable issue, that's all. So, in short,
no good reason. <wink>

Cheers,

// m

[Mike]

That makes life easy. Problem solved! Thanks all for the help.

Mike

You're lucky, functions "know" their name:

def func1(): pass ... def func2(): pass ... for f in [func1, func2]:

... print f.__name__
...
func1
func2

Peter