Explanation of Python variables and scopes, and explanation of python variable Fields

Explanation of Python variables and scopes, and explanation of python variable Fields

Scope

In python, the scope is divided into four situations: L: local, local scope, that is, the variables defined in the function;

E: enclosing: The local scope of nested parent functions, that is, the local scope of the upper-level functions that contain this function, but not global;

G: globa, global variable, which is defined at the module level; B: built-in, variable in the system fixed module, such as int and bytearray. The priority order of search variables is: local scope> outer scope> global in the current module> python built-in scope, that is, LEGB.

x = int(2.9) # int built-ing_count = 0 # globaldef outer():o_count = 1 # enclosingdef inner():i_count = 2 # local

Of course, local is relative to enclosing, And the enclosing variable is also local relative to the upper layer.

# Define variable a >>> a = 0 >>> print a0 # define FUNCTION p () >>> def p ():... print a... >>> p () 0 # define the function p2 () >>> def p2 ():... print... a = 3... print a... >>> p2 () # An error occurred while running. external variable a is referenced first and cannot be assigned Traceback (most recent call last): File "<interactive input>", line 1, in <module> File "<interactive input>", line 2, in p2UnboundLocalError: local variable 'A' referenced before assignment # define function p3 () >>> def p3 () :... a = 3 # assign values without referencing... print a... >>> p3 () 3 >>> print a0 # external variable a has not changed

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