Check if a variable exists

Question

I am using following method isset(var) to determine if a variable exists.

def isset(variable): try: variable except NameError: return False else: return True

It returns True if variable exists. But if a variable doesn't exist I get following:

Traceback (most recent call last): File "/usr/lib/python2.7/runpy.py", line 162, in _run_module_as_main "__main__", fname, loader, pkg_name) File "/usr/lib/python2.7/runpy.py", line 72, in _run_code exec code in run_globals File "/home/lenovo/pyth/master/vzero/__main__.py", line 26, in <module> ss.run() File "vzero/ss.py", line 4, in run snap() File "vzero/ss.py", line 7, in snap core.display() File "vzero/core.py", line 77, in display stdout(session(username())) File "vzero/core.py", line 95, in session if isset(ghi): #current_sessions[user]): NameError: global name 'ghi' is not defined

I don't want all these errors. I just want it return False. No output. How can I do this?

Your function won't work, because you are passing a variable to your function which doesn't exist. Otherwise your code is okay. — Ahasanul Haque
– Ahasanul Haque, Commented May 1, 2016 at 7:08

warvariuc · Accepted Answer · 2016-05-01 07:29:09Z

Instead of writing a complex helper function isset and calling it

if not isset('variable_name'): # handle the situation

in the place where you want to check the presence of the variable do:

try: # some code with the variable in question except NameError: # handle the situation

Actually, you point about stack frames is a thing I couldn't even consider. +1
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