This article describes the graphic python global variables and local variables relevant knowledge, the paper introduced by the sample code is very detailed, with some reference value of learning for all of us to learn or work, a friend in need can refer
Before looking at the global and local variables, we first look at the scope
a = 10
def func():
b = 20
def inner():
c = 30
To this program as an example above: print a, b, c
can see only a print 10, b and c are being given, this is the scope of the problem.
We put a .py file to see things a newly created module, a variable defined within a module, such as a, is a global variable of this module, acting on the overall situation, no matter in what can be called,
But b and c are defined inside a function, we called the local variables, can only act within the function. 
We look at a problem
func and inner functions can be called a variable it?
func function can be called variable c it?
The answer is: a global variable, you can call anywhere
but func function may not be called c, this time we put func seen as a whole, then the inner function is defined inside func, c is the inner internal variables 
Summary: variable definitions can be called from anywhere in the global definition, it can only be used within the function inside the function.
Variable lookup order: LEGB
Local scope> enclosing scope> current global module> Python built scope;
Two two methods on a global and local variables in it: global, nonlocal.
Directly on you an example: 
we can see that a locally defined, then we directly call a'll get an error
Only after the definition of call will be printed, and the value of a global variable will not change 
if I want to change the value of a local namespace how to do it? This time is necessary to use a global 
, we can see the value of a global variable has been modified to be 15.
The following is nonlocal: 
We see this when printing a, b, when wrong, the error message is no definition b
But a no error, this is because a global variables, and b is a local variable, so there is such a mistake, correct as follows: 
Because b is a local variable, so before calling with nonlocal statement, then you can call.
Namespaces
Namespace Classification
global namespace (Global): When creating each module loaded for execution, the variable record defined in the module, the module including a function defined in the class, introduction of other modules, module-level variables and constants.
Local namespace (Local): Each function has a name space, a record of all the variables defined in the function, the parameters including local variables function, internally defined.
Built-in namespace (Built-in): any module can be accessed, placed built-in functions and exceptions (such as: input, print, str, list , tuple ...).
Loading sequence namespace
Built-in namespace (before running load) a> global namespace (program execution: from top to bottom loading) a> local namespace (program execution: when the call load)
The value of the order of namespace
Local calls: a local namespace> a global namespace> Built namespace
In a global call: a global namespace> Built namespace
In summary, in the search for variables range from small, to large layer by layer to find the range.
Thank you very much to read
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