Check if variable exists in Python

Asked Jun 22 '17 at 17:44

Active Jun 22 '17 at 17:44

Viewed 30 times

I am trying to print a dictionary to screen, however, prior to its creation I want it to display nothing ("").

def dictionarysubmit():
    Letter = entry2.get()
    Rule = entry3.get()
    global grammar
    grammar = {}
    grammar[Letter] = Rule
##    print (grammar)

This is the creation of the dictionary, however is only prompt on button click.

I am currently trying:

cr = {}
if grammar in globals:
    cr = grammar
else:
    cr = {}

NameError: name 'grammar' is not defined

Is the error I am getting, I understand that grammar is not defined upon execution of the programme.

asked Jun 22 '17 at 17:44

E J

1

Use a `try ... except` block, keyed on `NameError` – Prune Jun 22 '17 at 17:46
@Prune Or just give `grammar` a default value of `{}`. – Christian Dean Jun 22 '17 at 17:48
Yes, why not use a `try ... except` block and if it does not exist then handle it in the `except` part. – DarkCygnus Jun 22 '17 at 17:48
Thanks to @Anthon for the reference. First use of my shiny, new `dupe-hammer`. :-) – Prune Jun 22 '17 at 17:50
Don't write your program in such a way. Initialize `grammer = None` and test for `grammer is None`. – Daniel Jun 22 '17 at 17:53
That's not true. You can easily check if `grammar` exists--check the duplicate link. – victor Jun 22 '17 at 17:54
Thank you all :) – E J Jun 22 '17 at 17:57

Check if variable exists in Python

0 Answers0