Programming Forums > Script Programming > Python

MR.T · Jun 15th, 2007, 2:49 AM

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 + ?

(Toggle Plain Text)

#!/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?

(Toggle Plain Text)

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:

(Toggle Plain Text)

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):

(Toggle Plain Text)

>>> 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():

(Toggle Plain Text)

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

Jun 15th, 2007, 2:49 AM	#1
MR.T Newbie Join Date: Feb 2006 Location: USA,Michigan Posts: 22 Rep Power: 0	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? __________________ "Gee, Brain, what do you want to do tonight?" "The same thing we do every night, Pinky: Try to take over the world!"

Jun 15th, 2007, 3:42 AM	#2
lectricpharaoh Caffeinated Neural Net Join Date: Jun 2005 Location: Dry west coast of Canada Posts: 1,033 Rep Power: 5	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#. __________________ And once again, Probability proves itself willing to sneak into a back alley and service Drama as would a copper-piece harlot. - Vaarsuvius, Order of the Stick

Jun 15th, 2007, 8:52 AM	#3
Infinite Recursion Programming Guru Join Date: Jul 2004 Location: United States Posts: 3,467 Rep Power: 8	How about using string concatenation via + ? (Toggle Plain Text) #!/usr/bin/python name = "Jason"; print "Hello " + name + ". How are you?"; #!/usr/bin/python name = "Jason"; print "Hello " + name + ". How are you?"; Execution: [jpowers@pandora ~]$ python string.py Hello Jason. How are you? __________________ http://jasonpowers.net "There are a thousand hacking at the branches of evil to one who is striking at the root."

Jun 15th, 2007, 8:59 AM	#4
Jessehk The Oblivious One Join Date: May 2005 Location: Ontario, Canada Posts: 644 Rep Power: 4	Something like this maybe? (Toggle Plain Text) 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() 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: (Toggle Plain Text) name = "Joe" print "Hello, %s!" % name name = "Joe" print "Hello, %s!" % name __________________ Dr. Zoidberg: [ecstatic] I'm going to a movie... with FRIENDS!

Jun 15th, 2007, 8:59 AM	#5
free-zombie Programmer Join Date: May 2006 Location: Bavaria, Germany Posts: 50 Rep Power: 0	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): (Toggle Plain Text) >>> 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')() >>> 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')()

Jun 15th, 2007, 12:53 PM	#6
MR.T Newbie Join Date: Feb 2006 Location: USA,Michigan Posts: 22 Rep Power: 0	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? __________________ "Gee, Brain, what do you want to do tonight?" "The same thing we do every night, Pinky: Try to take over the world!"

Jun 15th, 2007, 2:01 PM	#7
free-zombie Programmer Join Date: May 2006 Location: Bavaria, Germany Posts: 50 Rep Power: 0	I think I explained that in my code. You might want to read it carefully, especially lines 3, 4 and 6.

Jun 15th, 2007, 2:23 PM	#8
MR.T Newbie Join Date: Feb 2006 Location: USA,Michigan Posts: 22 Rep Power: 0	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. __________________ "Gee, Brain, what do you want to do tonight?" "The same thing we do every night, Pinky: Try to take over the world!"

Jun 28th, 2007, 12:10 PM	#9
Dietrich Professional Programmer Join Date: Feb 2005 Posts: 434 Rep Power: 4	I assume you found the evil function eval(): (Toggle Plain Text) joe = "this is what I want to print" bob = ["joe"] print eval(bob[0]) # this is what I want to print joe = "this is what I want to print" bob = ["joe"] print eval(bob[0]) # this is what I want to print __________________ I looked it up on the Intergnats!

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Programming Forums > Script Programming > Python

string to variable... or something