Global vs. Local variables

1. 定義在函式內的變數區域 (local) 變數，只限函式內存取；定義在函式外的全域 (global) 變數，則整個程式都可存取。

   [dywang@deyu zzz]$ cat function7.py
   #!/usr/bin/python3
   # coding: utf-8
   
   total = 0; # This is global variable.
   # Function definition is here
   def sum( arg1, arg2 ):
   	# Add both the parameters and return them."
   	total = arg1 + arg2; # Here total is local variable.
   	print("Inside the function local total :", total)
   	return total;
   
   # Now you can call sum function
   sum( 10, 20 );
   print("Outside the function global total :", total)
   

2. 執行結果：函式內的區域變數 total=30，函式外的全域變數 total=0。

   [dywang@deyu zzz]$ ./function7.py 
   Inside the function local total : 30
   Outside the function global total : 0
   

3. 設定 global 變數 total 為 sum 函式的回傳值。

   [dywang@deyu zzz]$ cat function7a.py
   #!/usr/bin/python3
   # coding: utf-8
   
   total = 0; # This is global variable.
   # Function definition is here
   def sum( arg1, arg2 ):
   	# Add both the parameters and return them."
   	total = arg1 + arg2; # Here total is local variable.
   	print("Inside the function local total :", total)
   	return total;
   
   # Now you can call sum function
   total = sum( 10, 20 );
   print("Outside the function global total :", total)
   

4. 執行結果：函式內的區域變數 total=30，函式外的全域變數 total=30。

   [dywang@deyu zzz]$ ./function7a.py 
   Inside the function local total : 30
   Outside the function global total : 30