Posted By: Anonymous
What I understand from reading the documentation is that Python has a separate namespace for functions, and if I want to use a global variable in that function, I need to use
I’m using Python 2.7 and I tried this little test
>>> sub = ['0', '0', '0', '0'] >>> def getJoin(): ... return '.'.join(sub) ... >>> getJoin() '0.0.0.0'
It seems things are working fine even without
global. I was able to access global variable without any problem.
Am I missing anything? Also, following is from Python documentation:
Names listed in a global statement
must not be defined as formal
parameters or in a for loop control
target, class definition, function
definition, or import statement.
While formal parameters and class definition make sense to me, I’m not able to understand the restriction on for loop control target and function definition.
global is only useful to change or create global variables in a local context, although creating global variables is seldom considered a good solution.
def bob(): me = "locally defined" # Defined only in local context print(me) bob() print(me) # Asking for a global variable
The above will give you:
locally defined Traceback (most recent call last): File "file.py", line 9, in <module> print(me) NameError: name 'me' is not defined
While if you use the
global statement, the variable will become available “outside” the scope of the function, effectively becoming a global variable.
def bob(): global me me = "locally defined" # Defined locally but declared as global print(me) bob() print(me) # Asking for a global variable
So the above code will give you:
locally defined locally defined
In addition, due to the nature of python, you could also use
global to declare functions, classes or other objects in a local context. Although I would advise against it since it causes nightmares if something goes wrong or needs debugging.