Overview:
- From an inner scope, the global keyword in Python binds a name to the global scope, so that a global variable can be assigned a value.
- Usage of global is not required, if the requirement is only to access the variable in the global scope but not assigning a value to it.
- Global scope is the outermost or topmost scope in Python.
- The difference between the keyword global and the keyword nonlocal is, global binds a name from an inner scope, directly to the next-to-last scope - global(The last scope or the outtermost scope is the namespace containing builtin names), while the nonlocal binds a name to the next outer scope, where that name is available.
How global can not be used:
- In the same code block, using a name as local for some distance (time) and using it as global for some distance (time) is not allowed.
- A formal parameter of a function cannot be defined as global inside that function.
Example – Behaviour while using the global keyword:
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# Example Python program that uses the global # keyword to bind a name to the global scope msg = "Hi";
def function1(): global msg; msg = "Hello"; print("Function1:",msg);
function1(); print("Global:", msg); |
Output:
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Function1: Hello Global: Hello |
Example - Behaviour while not using the global keyword:
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# Example Python program that uses the global # keyword to bind a name to the global scope msg = "Hi";
def function1(): msg = "Hello"; print("Function1:",msg);
function1(); print("Global:", msg); |
Output:
|
Function1: Hello Global: Hi |