Programming Forums - string to variable... or something

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MR.T	Jun 15th, 2007 2:49 AM

string to variable... or something

say I have a variable called example I want to print the contents of example, but I want to print it using its name from a string. Like so:

print "example"

naturally it will print the string example and not the contents of the variable example. How do I... de-string a string if you will?

lectricpharaoh

Jun 15th, 2007 3:42 AM

I've never used Python in my life, but what you want might be possible if the language has some mechanism for determining attributes at run time, similar to System.Runtime.Reflection in C#.

Infinite Recursion

Jun 15th, 2007 8:52 AM

How about using string concatenation via + ?

#!/usr/bin/python



name = "Jason";

print "Hello " + name + ". How are you?";

Execution:

[jpowers@pandora ~]$ python string.py
Hello Jason. How are you?

Jessehk

Jun 15th, 2007 8:59 AM

Something like this maybe?

class Person(object):

        def __init__(self, name, age):

                self.name = name

                self.age = age



def main():

        p = Person("Joe Smith", 38)

        attr = raw_input("Enter an attribute of a person: ")

        print "The person's %s is  %s." % (attr, getattr(p, attr))

        

if __name__ == "__main__":

        main()

EDIT: Ah, I think I misunderstood your question.
Too print the contents of a variable in a string, just use the "%s" specifier and follow it with an argument.

For example:

name = "Joe"

print "Hello, %s!" % name

free-zombie

Jun 15th, 2007 8:59 AM

In Python, there are two types of variables: locals and globals. Locals are variables defined inside functions/methods without the 'global' keyword, ones at module level are global.

Just some code now (with some other introspection to boot):

>>> a = 1

>>> def f():

...   b = 2

...   print locals()

...   print globals()

...   print locals()['b']

... 

>>> f()

{'b': 2}

{'__builtins__': <module '__builtin__' (built-in)>, '__name__': '__main__', '__doc__': None, 'a': 1, 'f': <function f at 0x2abb77914758>}

2

>>> class C:

...   def __init__(self):

...     print 'initializing nothing in particular'

...   def doNothing(self):

...     pass

... 

>>> dir(C)

['__doc__', '__init__', '__module__', 'doNothing']

>>> hasattr(C, 'doNothing')

True

>>> i = C()

initializing nothing in particular

>>> getattr(i, 'doNothing')

<bound method C.doNothing of <__main__.C instance at 0x2abb7791c9e0>>

>>> getattr(i, 'doNothing')()

MR.T	Jun 15th, 2007 12:53 PM

hmm, I I don't think I explained what I am trying to do very well. I guess what I am asking is kind of similar to unpickling. Let me try again to explain.

joe = "this is what I want to print"
bob = ["joe"]
print bob[0]

This would print the word "joe", but I want to actually print the value of joe which is "this is what I want to print". Is this possible?

free-zombie

Jun 15th, 2007 2:01 PM

I think I explained that in my code. You might want to read it carefully, especially lines 3, 4 and 6.

MR.T	Jun 15th, 2007 2:23 PM

Yes, free-zombie your post did explain what I was looking for.

I found out that there was a much simpler solution to the problem I was dealing with however. It seems like it is always like that with python and me, every time I do something I get hung up because I don't try the painfully simple and obvious things, I guess I just always expect it to be harder than it is.

Thanks for all the helpful replies guys.

Dietrich

Jun 28th, 2007 12:10 PM

I assume you found the evil function eval():

joe = "this is what I want to print"

bob = ["joe"]

print eval(bob[0])  # this is what I want to print

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