python这哪里错了,检查了好多遍啊

 #!/usr/bin/python
# Filename: func_global.py

def func():
  global x

print 'x is',x 在这显示global name 'x' is not defined
x = 2
print 'Changed local x to',x 

x = 50
func()
print 'Value of x is',x

你需要最开始定义x

  #!/usr/bin/python
# Filename: func_global.py

x = 0   #定义x

def func():
  global x

print 'x is',x 在这显示global name 'x' is not defined
x = 2
print 'Changed local x to',x 

x = 50
func()
print 'Value of x is',x