Define variables(Macro) in Python

Question

I am using python for one of my projects, and i want to define some variables like #define in C so that if i want to change the value i can change it only at one place.

I know that we can use global variables. But, I don't want to specify the keyword "global" in all the functions where I use the variables.

Actually I want something like this.(This is just a random example!)

DEFINE_MAX = 100

def function1(num):
    return num < DEFINE_MAX

def function2(num):
    return num > DEFINE_MAX

The variable DEFINE_MAX might be used through out the application. So I want to define it at one common place.

So how can I do this in python?

In future, try running your code first - you have literally solved your own question. — Gareth Latty
– Gareth Latty, Commented Jul 29, 2014 at 7:35

holdenweb · Accepted Answer · 2016-12-16 11:09:59Z

14

First, if your functions don't need write access to the global variables then there is no need to declare them global inside the functions. They will be found by the usual three-namespace (local, global, builtins) name resolution search. If you ARE writing to global variables then please reconsider your design.

The code sample you provided is perfectly good Python and effectively gives you the central control you appear to need over program parameters.

Just to throw in a bit of jargon, such values are often referred to as symbolic or manifest constants.

edited Dec 16, 2016 at 11:09

answered Jul 29, 2014 at 7:34

holdenweb

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3 Comments

user2109788 Over a year ago

Thanks! I did not know that, only in write access to the global variable i need to define it as global.

holdenweb Over a year ago

Now you do. Isn't Stackoverflow great?

holdenweb Over a year ago

System such as Django go one further and define a settings module that any code needing access to application settings can import.

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