Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #11761 > unrolled thread

How to convert a list of strings into a list of variables

Back to article view | Back to comp.lang.python

Contents

  How to convert a list of strings into a list of variables noydb <jenn.duerr@gmail.com> - 2011-08-18 07:57 -0700
    Re: How to convert a list of strings into a list of variables David Robinow <drobinow@gmail.com> - 2011-08-18 11:12 -0400
      Re: How to convert a list of strings into a list of variables noydb <jenn.duerr@gmail.com> - 2011-08-18 08:19 -0700
        Re: How to convert a list of strings into a list of variables Jerry Hill <malaclypse2@gmail.com> - 2011-08-18 11:29 -0400
          Re: How to convert a list of strings into a list of variables noydb <jenn.duerr@gmail.com> - 2011-08-18 08:54 -0700
    Re: How to convert a list of strings into a list of variables John Gordon <gordon@panix.com> - 2011-08-18 16:09 +0000
      Re: How to convert a list of strings into a list of variables Chris Angelico <rosuav@gmail.com> - 2011-08-18 18:48 +0100
        Re: How to convert a list of strings into a list of variables Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-19 11:42 +1000
      Re: How to convert a list of strings into a list of variables Nobody <nobody@nowhere.com> - 2011-08-18 19:45 +0100
        Re: How to convert a list of strings into a list of variables AB <antonio.a.barbosa@gmail.com> - 2011-08-18 15:05 -0700
    Re: How to convert a list of strings into a list of variables Kingsley Adio <adiksonline@gmail.com> - 2011-08-19 00:39 -0700
    Re: How to convert a list of strings into a list of variables Roy Smith <roy@panix.com> - 2011-08-19 08:57 -0400
      Re: How to convert a list of strings into a list of variables noydb <jenn.duerr@gmail.com> - 2011-08-19 07:32 -0700

#11761 — How to convert a list of strings into a list of variables

How would you convert a list of strings into a list of variables using
the same name of the strings?

So, ["red", "one", "maple"] into [red, one, maple]

Thanks for any help!

[toc] | [next] | [standalone]

#11767

On Thu, Aug 18, 2011 at 10:57 AM, noydb <jenn.duerr@gmail.com> wrote:
> How would you convert a list of strings into a list of variables using
> the same name of the strings?
>
> So, ["red", "one", "maple"] into [red, one, maple]
  Why would you want to?

[toc] | [prev] | [next] | [standalone]

#11768

On Aug 18, 11:12 am, David Robinow <drobi...@gmail.com> wrote:
> On Thu, Aug 18, 2011 at 10:57 AM, noydb <jenn.du...@gmail.com> wrote:
> > How would you convert a list of strings into a list of variables using
> > the same name of the strings?
>
> > So, ["red", "one", "maple"] into [red, one, maple]
>
>   Why would you want to?

I am being passed the list of strings.  I have variables set up
already pointing to files.  I need to loop through each variable in
the list and do things to the files.  The list of strings will change
each time, include up to 22 of the same strings each time.

[toc] | [prev] | [next] | [standalone]

#11769

On Thu, Aug 18, 2011 at 11:19 AM, noydb <jenn.duerr@gmail.com> wrote:
> I am being passed the list of strings.  I have variables set up
> already pointing to files.  I need to loop through each variable in
> the list and do things to the files.  The list of strings will change
> each time, include up to 22 of the same strings each time.

If you have a mapping of strings to values, you should just go ahead
and store them in a dictionary.  Then the lookup becomes simple:

def foo(list_of_strings):
	mapping = {
		"bar0": "/var/log/bar0.log",
		"bar1": "/usr/local/bar/bar1.txt",
		"bar2": "/home/joe/logs/bar2.log",
	}
	for item in list_of_strings:
		filename = mapping[item]
		do_something(filename)


(Untested)

-- 
Jerry

[toc] | [prev] | [next] | [standalone]

#11771

On Aug 18, 11:29 am, Jerry Hill <malaclyp...@gmail.com> wrote:
> On Thu, Aug 18, 2011 at 11:19 AM, noydb <jenn.du...@gmail.com> wrote:
> > I am being passed the list of strings.  I have variables set up
> > already pointing to files.  I need to loop through each variable in
> > the list and do things to the files.  The list of strings will change
> > each time, include up to 22 of the same strings each time.
>
> If you have a mapping of strings to values, you should just go ahead
> and store them in a dictionary.  Then the lookup becomes simple:
>
> def foo(list_of_strings):
>         mapping = {
>                 "bar0": "/var/log/bar0.log",
>                 "bar1": "/usr/local/bar/bar1.txt",
>                 "bar2": "/home/joe/logs/bar2.log",
>         }
>         for item in list_of_strings:
>                 filename = mapping[item]
>                 do_something(filename)
>
> (Untested)
>
> --
> Jerry

Thanks, implemented something along those lines, and it worked!

[toc] | [prev] | [next] | [standalone]

#11775

In <2ab25f69-6017-42a6-a7ef-c71bc2ee8547@l2g2000vbn.googlegroups.com> noydb <jenn.duerr@gmail.com> writes:

> How would you convert a list of strings into a list of variables using
> the same name of the strings?

> So, ["red", "one", "maple"] into [red, one, maple]

> Thanks for any help!

If the strings and the object names are exactly the same, you could use
eval().  (Of course this assumes the objects already exist.)

  red = "this is the red object"
  one = 1
  maple = "this is the maple object"

  list_of_strings = ["red", "one", "maple"]
  list_of_variables = []

  for x in list_of_strings:
    list_of_variables.append(eval(x))

  for y in list_of_variables:
    print y

-- 
John Gordon                   A is for Amy, who fell down the stairs
gordon@panix.com              B is for Basil, assaulted by bears
                                -- Edward Gorey, "The Gashlycrumb Tinies"

[toc] | [prev] | [next] | [standalone]

#11790

On Thu, Aug 18, 2011 at 5:09 PM, John Gordon <gordon@panix.com> wrote:
> for x in list_of_strings:
>    list_of_variables.append(eval(x))
>

If this really is what you need, you can simplify it by using the
globals() dictionary - it's a regular dictionary whose contents are
all the global variables in your current module. Inside a function,
use locals() instead.

http://docs.python.org/library/functions.html#globals

ChrisA

[toc] | [prev] | [next] | [standalone]

#11821

Chris Angelico wrote:

> On Thu, Aug 18, 2011 at 5:09 PM, John Gordon <gordon@panix.com> wrote:
>> for x in list_of_strings:
>> list_of_variables.append(eval(x))
>>
> 
> If this really is what you need, you can simplify it by using the
> globals() dictionary - it's a regular dictionary whose contents are
> all the global variables in your current module. Inside a function,
> use locals() instead.

You can use locals outside of a function too, because it just returns
globals().

Lookup of names in locals/globals is much safer than eval, particularly if
there is any risk that the list of names comes from an untrusted or 
potentially hostile source.

list_of_strings = ['red', 'blue', 
    '__import__("os").system("echo I just p0wned your system")',
    'green', 'yellow']

(The simplest way out of a billion to cause grief.)

Code injection attacks are the first and second most common form of security
vulnerability, ahead of even buffer overflows. Please don't add to the
list.

http://cwe.mitre.org/top25/?2011

(Oh, and if you think that protecting against code injection attacks while
still using eval or exec is simple, please step away from the keyboard.)



-- 
Steven

[toc] | [prev] | [next] | [standalone]

#11798

On Thu, 18 Aug 2011 16:09:43 +0000, John Gordon wrote:

>> How would you convert a list of strings into a list of variables using
>> the same name of the strings?
> 
>> So, ["red", "one", "maple"] into [red, one, maple]
> 
> If the strings and the object names are exactly the same, you could use
> eval().

Eval is overkill for variables; use globals() and/or locals().

But data which is supposed to be indexed by a variable key (i.e. a name
which is determined at run-time) should normally be put into a dictionary.
If access with fixed keys is far more common than variable keys, using an
object (with getattr/setattr for variable keys) may be preferable.

[toc] | [prev] | [next] | [standalone]

#11811

Hi,

If the «variables» are named attributes you can use getattr.


#----------------
class colors:
	red=1
	green=2
	blue=3
	
c=colors()

a=['red','green','blue']

for v in a:
	print v,getattr(c,v)
#-----------

AB

[toc] | [prev] | [next] | [standalone]

#11833

noydb wrote:
> How would you convert a list of strings into a list of variables using
> the same name of the strings?
>
> So, ["red", "one", "maple"] into [red, one, maple]
>
> Thanks for any help!

red="a string"
one="another string"
maple="a file path"
old=["red", "one", "maple"]
newList=map(eval, old)

[toc] | [prev] | [next] | [standalone]

#11840

In article 
<2ab25f69-6017-42a6-a7ef-c71bc2ee8547@l2g2000vbn.googlegroups.com>,
 noydb <jenn.duerr@gmail.com> wrote:

> How would you convert a list of strings into a list of variables using
> the same name of the strings?
> 
> So, ["red", "one", "maple"] into [red, one, maple]
> 
> Thanks for any help!

I'm not sure what you're trying to do, but explore the dictionary 
returned by locals().  You can do something like:

loc = locals()
[loc["red"], loc["one"], loc["maple"]]

[toc] | [prev] | [next] | [standalone]

#11842

Thanks to all for your responses!  Good lessons.  I implemented
something like what Jerry Hill suggested (dictionary), which works
well for my purposes.  The list of strings that is being passed into
this code is also provided by something I wrote so I do trust what is
being sent.  Might use what AB suggested down the line, as tool
expands.  Thanks!

[toc] | [prev] | [standalone]

Back to top | Article view | comp.lang.python

csiph-web