If you need this, you’re probably doing it wrong. But if you really must check to see if a variable has been assigned yet, there’s nothing really stopping you. Here’s one way of implementing it.

Just wrap what you’re doing in a short try/except clause. Simple. Now you can tell if “variable” is defined without dying in a fire.

try: x = variable del x print "%s is defined" % variable except NameError: print "%s is not defined" % variable

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try:     x = variable     del x     print "%s is defined" % variable except NameError:     print "%s is not defined" % variable

Too bad you can’t wrap this in a function definition. Well, you can – sort of. If you make this a function, it will work as long as the variable you give it is already defined. If not, you’ll still get a NameError. If you wrap the function call in try/except, it will work! I guess if you’re trying really hard to fail and you need isset() several times in your code, at least it will look nice.

def isset(variable) try: x = variable del x except NameError: return False return True try: if isset(my_var): print "do stuff..." except: pass

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def isset(variable)     try:         x = variable         del x     except NameError:         return False     return True   try:     if isset(my_var):         print "do stuff..." except:     pass

Disclaimer: writing in one language while thinking in another is probably a bad idea…

Posted on June 20th, by admica in fail, programming.

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