Question

Why does this print 4?

http://dpaste.com/779443/

Shouldn't it need a line inside the function like "global a", so "a" is in the function scope and not only in the main scope?

Answer 1

this print 4 because your code is very simple. in python you variable "a" is global Every time a function gets called, Python creates a new function frame, which contains the function's local variables and parameters.

global a ----> 1.. never change
within the function you create variable "a" applies only to the function

Answer 2

Because your function "f(x)" add the value of x to the value of a (which is always 1).

Answer 3

so simple 4... f send 3 as arguments to f which add 1 and return it to print and it prints it

Answer 4

For your answers I can see that I didn't express myself well. My question is related to the use of "global" and scopes.

In that code we have:

Main Scope:
- a
- f(x)

f(x) Scope:

- x

So the object a is not in the function scope. How can the function use it without a "global a" line in the function?

Answer 5

The point is that works in the other way: 'a' is a global variable because is declared in the main program, then it is in the scope of the whole program (functions included).

And you can use "global var" in the function definition to make the variable global and share that variable to use in other functions (even the main function).

Answer 6

I just ran some experiments and reached some conclusions that need confirmation. Objects in outermost scopes can always be used in inner scopes without using "global"?

If f(x) and g(x) are too independent functions, to use in g an object created inside f we need to write "global object" in f?

Answer 7

That confirms what I suspected from recent results. Really thanks choutos and everyone else.