Converting string to argument

[Laughlin, Joseph V]

class Foo:
x = "blah"
y = "blah some more"

foo = Foo()
x_string = "x"
y_string = "y"

# I want something like this to work:
print foo.x_string
print foo.y_string
# The above should print out "blah" and "blah some more"
# Any ideas?
# Let me know if I need to clarify anything.




Joe Laughlin
NCO Simulation Labs
Integrated Defense Systems
The Boeing Company

 

[Heather Coppersmith]

class Foo:
x = "blah"
y = "blah some more"

foo = Foo()
x_string = "x"
y_string = "y"

# I want something like this to work:
print foo.x_string
print foo.y_string
# The above should print out "blah" and "blah some more"
# Any ideas?
# Let me know if I need to clarify anything.

The usual comp.lang.python answer is "why do you want to do this?"

In most cases, wanting to do this is a symptom of something else
being sub-optimal. Perhaps it's as simple as putting x and y into
a dictionary instead of creating them as class attributes:

foo = { }
foo[ "x" ] = "blah"
foo[ "y" ] = "blah some more"

x_string = "x"
y_string = "y"

print foo[ x_string ]
print foo[ y_string ]

Regards,
Heather

 

[Brian Jones]

The usual comp.lang.python answer is "why do you want to do this?"

In most cases, wanting to do this is a symptom of something else
being sub-optimal. Perhaps it's as simple as putting x and y into
a dictionary instead of creating them as class attributes:

I think a good reason for wanting to map string values into literal
variables/methods/classes such as Joseph explained, is so that they
can be dynamically defined in something such as a config file, for
example.

I wrote a simple application which had a basic text based
configuration file, and a key/value pair defined as:

MODULES = mod1, mod2, ..modN

.... where each module was seperated by commas, and read into the
application as strings. getattr() and __import__() proved very useful
at this point, allowing me to dynamically load the modules, and the
classes within using the config string values.


-- Brian Jones

 

[Tobiah]

What you really want is this:

class Foo:
x = "blah"
y = "blah some more"


foo = Foo()

x_string = 'x'
y_string = 'y'

print eval('foo.' + x_string)
print eval('foo.' + y_string)

 

[Tobiah]

What you really want is this:

class Foo:
x = "blah"
y = "blah some more"


foo = Foo()

x_string = 'x'
y_string = 'y'

print eval('foo.' + x_string)
print eval('foo.' + y_string)

 

[Tristan Seligmann]

What you really want is this:

class Foo:
x = "blah"
y = "blah some more"


foo = Foo()

x_string = 'x'
y_string = 'y'

print eval('foo.' + x_string)
print eval('foo.' + y_string)

Using eval is overkill; something like:

print getattr(foo, x_string)
print getattr(foo, y_string)

should work just fine. In general, I'd suggest avoiding the use of eval
unless you really want something involving arbitrary code execution.
--
mithrandi, i Ainil en-Balandor, a faer Ambar

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