Using string as variable name

Question

Is there any way for me to use a string to call a method of a class? Here's an example that will hopefully explain better (using the way I think it should be):

class helloworld():
 def world(self):
 print "Hello World!"
str = "world"
hello = helloworld()
hello.`str`()

Which would output Hello World!.

Thanks in advance.

• Buddy: Should the output be "hello world" or "Hello World!"?

Answer 1

You can use getattr:

>>> class helloworld:
... def world(self):
... print("Hello World!")
... 
>>> m = "world"
>>> hello = helloworld()
>>> getattr(hello, m)()
Hello World!

• Note that the parens in class helloworld() as in your example are unnecessary, in this case.
• And, as SilentGhost points out, str is an unfortunate name for a variable.

• SilentGhost: str is a bad choice for a variable name.

Answer 2

Warning: exec is a dangerous function to use, study it before using it

You can also use the built-in function "exec":

>>> def foo(): print('foo was called');
...
>>> some_string = 'foo';
>>> exec(some_string + '()');
foo was called
>>>

• Stephan202: The is really not a good idea. exec should be avoided when possible. getattr is made for this problem.
• AgentLiquid: Don't confuse how to do something with whether it's safe or not. exec is indeed a dangerous function to use. However, there are ways to use it safely. In this case, you can pass the "globals" and "locals" context dictionaries in order to run exec in a "sandbox".
• Steve Gattuso: I've heard awful things about exec(), but this worked perfectly.
• AgentLiquid: Keep in mind, Sliggy, that exec is indeed dangerous to use. Make sure you fully understand the weapon before handling it.

Answer 3

What you're looking for is exec

class helloworld():
 def world(self):
 print "Hello World!"
str = "world"
hello = helloworld()
completeString = "hello.%s()" % str
exec(completString)

• Peter Ericson: I have never used "exec" before but I think I'll reconsider... Up-modding.

Answer 4

one way is you can set variables to be equal to functions just like data

def thing1():
 print "stuff"
def thing2():
 print "other stuff"
avariable = thing1
avariable ()
avariable = thing2
avariable ()

And the output you'l get is

stuff
other stuff

Then you can get more complicated and have

somedictionary["world"] = world
somedictionary["anotherfunction"] = anotherfunction

and so on. If you want to automatically compile a modules methods into the dictionary use dir()

• a_m0d: How can you get the output of thing1 by calling blah?