Easy way to check that variable is defined in python?

Question

Hello.

Is it any way to check if a variable (class member or standalone) with specified name defined? Example:

if "myVar" in myObject.__dict__ : # not an easy way
  print myObject.myVar
else
  print "not defined"

Answer 1

try:
    print myObject.myVar
except NameError:
    print "not defined"

Answer 2

Paolo is right, there may be something off with the way you're doing things if this is needed. But if you're just doing something quick and dirty you probably don't care about Idiomatic Python anway, then this may be shorter.

try: x
except: print "var doesn't exist"

Answer 3

A compact way:

print myObject.myVar if hasattr(myObject, 'myVar') else 'not defined'

htw's way is more Pythonic, though.

hasattr() is different from x in y.__dict__, though: hasattr() takes inherited class attributes into account, as well as dynamic ones returned from __getattr__, whereas y.__dict__ only contains those objects that are attributes of the y instance.