Programming Forums > Script Programming > Python

Minion · Jul 19th, 2005, 1:30 AM

Okay, I will be quick and to the point. The below code returns a NameError: global name 'troid' is not defined.

Can someone tell me what I did wrong?

(Toggle Plain Text)

#Metroid Pet Sim
#Written by Alex Johnson
#If someone tells you otherwise shove him into a 'Troid nuts-first.

def main():
    print "Metroid pet-sim in development!"
    troid = raw_input("Name your new baby Metroid! ")
    prompt()
def prompt():
    print troid
main()

sykkn · Jul 19th, 2005, 4:58 AM

your problem is scope ... in python variables created (first use) in a function only have scope in that function and therefore do not exist once the function has completed. try moving your variable outside of the function or returning it from main() and passing it to prompt()

check http://www.python.org/doc for scope rules.

Dietrich · Jul 19th, 2005, 6:59 AM

You need to define your function before you call it. Also make troid global so the other function can use it.

(Toggle Plain Text)

#If someone tells you otherwise shove him into a 'Troid nuts-first.

def prompt():
    print troid

def main():
    global troid
    print "Metroid pet-sim in development!"
    troid = raw_input("Name your new baby Metroid! ")
    prompt()


main()

Cerulean · Jul 19th, 2005, 9:19 AM

You don't need to define your function before you use it.

(Toggle Plain Text)

>>> def foo():   
  .     bar()
  .     
>>> def bar():
  .     print "Yeah.."
  .     
>>> foo()
Yeah.

You do, however, need to make troid global in this example, but the better solution is to pass the troid variable as a parameter to the prompt function, like so:

(Toggle Plain Text)

def prompt(s):
    print s

def main():
    print "Metroid ..."
    troid = raw_input("Name your ...")
    prompt(troid)

Minion · Jul 19th, 2005, 11:14 PM

Okay, thanks. Because of the way I'm used to programming I'm just going to be making all variables global, now that I know you can (and need) to do that. I simply assumed they were always global.

Cerulean · Jul 20th, 2005, 7:41 AM

Quote:

Because of the way I'm used to programming I'm just going to be making all variables global

Eeek. Global variables are great when used properly, but just using them as a general rule in any programming language is bad (explaned by Wikipedia). It's bad in Python specifically because accessing global variables is a slower and more costly than accessing local variables.

Infinite Recursion · Jul 20th, 2005, 8:08 AM

I agree, regardless of the language... keep the use of global variables down as much as possible. There is a reason for variable scoping

Dietrich · Jul 20th, 2005, 8:20 AM

[quote=Cerulean]You don't need to define your function before you use it.

(Toggle Plain Text)

>>> def foo():   
  .     bar()
  .     
>>> def bar():
  .     print "Yeah.."
  .     
>>> foo()
Yeah.

The silly command line scribbles prove nothing. Try this

(Toggle Plain Text)

# define a function before it is called or get an error

print doubleValue(5)  # gives NameError: name 'doubleValue' is not defined

def doubleValue(n):
    n = n * 2
    return n

Ooble · Jul 20th, 2005, 3:34 PM

Dietrich is right. You do need to declare and define a function before you use it, but not before you tell the computer it may be used in the future.

Cerulean · Jul 20th, 2005, 3:52 PM

Quote:

Originally Posted by Dietrich

The silly command line scribbles prove nothing. Try this

(Toggle Plain Text)

# define a function before it is called or get an error

print doubleValue(5)  # gives NameError: name 'doubleValue' is not defined

def doubleValue(n):
    n = n * 2
    return n

By "use it", I did not mean call it. I meant reference it in another function. I'm afraid your code example is the flawed one. Please look at his example, which uses code like the code used in my "command line scribble". As you see, he calls the main function at the bottom of the file, after the definition of main and troid. In his example, his error had nothing to do with where the prompt function was placed.

Jul 19th, 2005, 1:30 AM	#1
Minion Newbie Join Date: Jul 2005 Posts: 3 Rep Power: 0	Weird NameError Okay, I will be quick and to the point. The below code returns a NameError: global name 'troid' is not defined. Can someone tell me what I did wrong? (Toggle Plain Text) #Metroid Pet Sim #Written by Alex Johnson #If someone tells you otherwise shove him into a 'Troid nuts-first. def main(): print "Metroid pet-sim in development!" troid = raw_input("Name your new baby Metroid! ") prompt() def prompt(): print troid main() #Metroid Pet Sim #Written by Alex Johnson #If someone tells you otherwise shove him into a 'Troid nuts-first. def main(): print "Metroid pet-sim in development!" troid = raw_input("Name your new baby Metroid! ") prompt() def prompt(): print troid main()

Jul 19th, 2005, 4:58 AM	#2
sykkn Hobbyist Programmer Join Date: Apr 2004 Location: Texas Posts: 106 Rep Power: 5	your problem is scope ... in python variables created (first use) in a function only have scope in that function and therefore do not exist once the function has completed. try moving your variable outside of the function or returning it from main() and passing it to prompt() check http://www.python.org/doc for scope rules. __________________ [ [ SykkN alloc ] initWithThePowerTo: destroyYouAll ]; /* Don't make me use it! */

Jul 19th, 2005, 6:59 AM	#3
Dietrich Professional Programmer Join Date: Feb 2005 Posts: 434 Rep Power: 4	You need to define your function before you call it. Also make troid global so the other function can use it. (Toggle Plain Text) #If someone tells you otherwise shove him into a 'Troid nuts-first. def prompt(): print troid def main(): global troid print "Metroid pet-sim in development!" troid = raw_input("Name your new baby Metroid! ") prompt() main() #If someone tells you otherwise shove him into a 'Troid nuts-first. def prompt(): print troid def main(): global troid print "Metroid pet-sim in development!" troid = raw_input("Name your new baby Metroid! ") prompt() main() __________________ I looked it up on the Intergnats!

Jul 19th, 2005, 9:19 AM	#4
Cerulean Professional Programmer Join Date: Apr 2005 Location: London, England Posts: 459 Rep Power: 4	You don't need to define your function before you use it. (Toggle Plain Text) >>> def foo(): . bar() . >>> def bar(): . print "Yeah.." . >>> foo() Yeah. >>> def foo(): . bar() . >>> def bar(): . print "Yeah.." . >>> foo() Yeah. You do, however, need to make troid global in this example, but the better solution is to pass the troid variable as a parameter to the prompt function, like so: (Toggle Plain Text) def prompt(s): print s def main(): print "Metroid ..." troid = raw_input("Name your ...") prompt(troid) def prompt(s): print s def main(): print "Metroid ..." troid = raw_input("Name your ...") prompt(troid)

Jul 19th, 2005, 11:14 PM	#5
Minion Newbie Join Date: Jul 2005 Posts: 3 Rep Power: 0	Okay, thanks. Because of the way I'm used to programming I'm just going to be making all variables global, now that I know you can (and need) to do that. I simply assumed they were always global. __________________ (Toggle Plain Text) def repeat(): lather() rinse() repeat() def repeat(): lather() rinse() repeat() And thus, the story of the programmer who died of old age while washing his hair.

Jul 20th, 2005, 8:08 AM	#7
Infinite Recursion Programming Guru Join Date: Jul 2004 Location: United States Posts: 3,467 Rep Power: 8	I agree, regardless of the language... keep the use of global variables down as much as possible. There is a reason for variable scoping __________________ http://jasonpowers.net "There are a thousand hacking at the branches of evil to one who is striking at the root."

Jul 20th, 2005, 8:20 AM	#8
Dietrich Professional Programmer Join Date: Feb 2005 Posts: 434 Rep Power: 4	[quote=Cerulean]You don't need to define your function before you use it. (Toggle Plain Text) >>> def foo(): . bar() . >>> def bar(): . print "Yeah.." . >>> foo() Yeah. >>> def foo(): . bar() . >>> def bar(): . print "Yeah.." . >>> foo() Yeah. The silly command line scribbles prove nothing. Try this (Toggle Plain Text) # define a function before it is called or get an error print doubleValue(5) # gives NameError: name 'doubleValue' is not defined def doubleValue(n): n = n * 2 return n # define a function before it is called or get an error print doubleValue(5) # gives NameError: name 'doubleValue' is not defined def doubleValue(n): n = n * 2 return n __________________ I looked it up on the Intergnats!

Jul 20th, 2005, 3:34 PM	#9
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	Dietrich is right. You do need to declare and define a function before you use it, but not before you tell the computer it may be used in the future. __________________ Me :: You :: Them

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Programming Forums > Script Programming > Python

Weird NameError