How to give a global variable to a function which is in a module?

[Kurda Yon]

Hi,

I would like to declare a global variable, which is seen to a
particular function. If I do as the following it works:

x = 1
def test():
global x
print x
return 1

However, it does not helps since my function is in a separate file. In
other words I have a main program which has the following structure:

from test import test
x = 1
y = test()

and I have a test.py file which contains the "test" function:
def test():
global x
print x
return 1

In this case the test does not see the global variable x. How can I
make the x to be visible?

Thank you.

 

[Bruno Desthuilliers]

Kurda Yon a écrit :

Hi,

I would like to declare a global variable, which is seen to a
particular function.

First point : there's no real 'global' scope in Python. 'global' really
means 'module-level'.

Second point : globals are Bad(tm) anyway.

If I do as the following it works:

x = 1
def test():
global x
print x
return 1

You don't even need the global statement here, since you're not
rebinding x within the function.

However, it does not helps since my function is in a separate file. In
other words I have a main program which has the following structure:

from test import test
x = 1
y = test()

That's obviously something you *don't* want - functions depending on
global variables that can be changed from anywhere. Ok, like any golden
rule, this one is meant to be bypassed sometimes, but unless you fully
understand why this is 99 times out of 100 a BadThing(tm) to do, just
don't do it.

for the record, this would work:

import test
test.x = 42
y = test()

But once again : unless you really know what you're doing and why you're
doing it, just don't do it.

and I have a test.py file which contains the "test" function:
def test():
global x
print x
return 1

In this case the test does not see the global variable x. How can I
make the x to be visible?

Pass it to the function.

# test.py
def test(x):
print x
return x + 42

# main.py
from test import test
y = test(2)

 

[Terry Reedy]

Hi,

I would like to declare a global variable, which is seen to a
particular function. If I do as the following it works:

x = 1
def test():
global x
print x
return 1

If you are just reading x, the global statement does nothing and is not
needed.

However, it does not helps since my function is in a separate file. In
other words I have a main program which has the following structure:

from test import test
x = 1
y = test()

and I have a test.py file which contains the "test" function:
def test():
global x
print x
return 1

In this case the test does not see the global variable x. How can I
make the x to be visible?

'Global' means 'global to the current module in which the global
statement appears. Yes this is confusing. 'Modular' would be more
exact, but 'global' goes back to before Python when there were no
separate modules connected together.

Either pass x to the function (probably best) or put x into the imported
module with 'test.x = 1".

Terry Jan Reedy