如何在 python 函数中使用全局变量？
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How do I use global variables in python functions?
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如何在 python 函数中设置全局变量？
要在函数内部使用global变量，你需要在函数内部使用global <varName>，像这样。
testVar = 0
def testFunc():
global testVar
testVar += 1
print testVar
testFunc()
print testVar
>>>
0
1
def testFunc2():
print testVartestVar = []
def testFunc1():
testVar = [2] # Will create a local testVar and assign it [2], but will not change the global variable.
def testFunc2():
global testVar
testVar = [2] # Will change the global variable.
def testFunc3():
testVar.append(2) # Will change the global variable.
count = 0
def funct():
global count
count += 1
return count
print funct() # prints 1
a = funct() # a = 2
print funct() # prints 3
print a # prints 2
print count # prints 3
def initCounter():
count = 0
def incrementCounter():
count += 1
return count
#notice how you're returning the function with no parentheses
#so you return a function instead of a value
return incrementCounter
myFunct = initCounter()
print myFunct() # prints 1
a = myFunct() # a = 2
print myFunct() # prints 3
print a # prints 2
print count # raises an error!
# So you can use count for something else if needed!
a = 1
def f():
# uses global because it hasn't been rebound
print 'f: ',a
def g():
# variable is rebound so global a isn't touched
a = 2
print 'g: ',a
def h():
# specify that the a we want is the global variable
global a
a = 3
print 'h: ',a
print 'global: ',a
f()
print 'global: ',a
g()
print 'global: ',a
h()
print 'global: ',a
global: 1
f: 1
global: 1
g: 2
global: 1
h: 3
global: 3
>>> c = 1
>>> def foo():
... c = 0
... c += 1
... print c
...
>>> def bar():
... global c
... c += 1
... print c
...
>>> foo()
1
>>> foo()
1
>>> foo()
1
>>> bar()
2
>>> bar()
3
#function
def test_f(x):
y = x + 2
return y
#execute function, and assign result as another variable
var = test_f(3)
#can use the output of test_f()!
print var #returns 5
print var + 3 #returns 8给出输出
testVar = 0
def testFunc():
global testVar
testVar += 1
print testVar
testFunc()
print testVar
>>>
0
1
def testFunc2():
print testVartestVar = []
def testFunc1():
testVar = [2] # Will create a local testVar and assign it [2], but will not change the global variable.
def testFunc2():
global testVar
testVar = [2] # Will change the global variable.
def testFunc3():
testVar.append(2) # Will change the global variable.
count = 0
def funct():
global count
count += 1
return count
print funct() # prints 1
a = funct() # a = 2
print funct() # prints 3
print a # prints 2
print count # prints 3
def initCounter():
count = 0
def incrementCounter():
count += 1
return count
#notice how you're returning the function with no parentheses
#so you return a function instead of a value
return incrementCounter
myFunct = initCounter()
print myFunct() # prints 1
a = myFunct() # a = 2
print myFunct() # prints 3
print a # prints 2
print count # raises an error!
# So you can use count for something else if needed!
a = 1
def f():
# uses global because it hasn't been rebound
print 'f: ',a
def g():
# variable is rebound so global a isn't touched
a = 2
print 'g: ',a
def h():
# specify that the a we want is the global variable
global a
a = 3
print 'h: ',a
print 'global: ',a
f()
print 'global: ',a
g()
print 'global: ',a
h()
print 'global: ',a
global: 1
f: 1
global: 1
g: 2
global: 1
h: 3
global: 3
>>> c = 1
>>> def foo():
... c = 0
... c += 1
... print c
...
>>> def bar():
... global c
... c += 1
... print c
...
>>> foo()
1
>>> foo()
1
>>> foo()
1
>>> bar()
2
>>> bar()
3
#function
def test_f(x):
y = x + 2
return y
#execute function, and assign result as another variable
var = test_f(3)
#can use the output of test_f()!
print var #returns 5
print var + 3 #returns 8请记住，如果您想进行分配/更改它们，您只需要在函数内声明它们 global。打印和访问不需要 global。
你可以的，
testVar = 0
def testFunc():
global testVar
testVar += 1
print testVar
testFunc()
print testVar
>>>
0
1
def testFunc2():
print testVartestVar = []
def testFunc1():
testVar = [2] # Will create a local testVar and assign it [2], but will not change the global variable.
def testFunc2():
global testVar
testVar = [2] # Will change the global variable.
def testFunc3():
testVar.append(2) # Will change the global variable.
count = 0
def funct():
global count
count += 1
return count
print funct() # prints 1
a = funct() # a = 2
print funct() # prints 3
print a # prints 2
print count # prints 3
def initCounter():
count = 0
def incrementCounter():
count += 1
return count
#notice how you're returning the function with no parentheses
#so you return a function instead of a value
return incrementCounter
myFunct = initCounter()
print myFunct() # prints 1
a = myFunct() # a = 2
print myFunct() # prints 3
print a # prints 2
print count # raises an error!
# So you can use count for something else if needed!
a = 1
def f():
# uses global because it hasn't been rebound
print 'f: ',a
def g():
# variable is rebound so global a isn't touched
a = 2
print 'g: ',a
def h():
# specify that the a we want is the global variable
global a
a = 3
print 'h: ',a
print 'global: ',a
f()
print 'global: ',a
g()
print 'global: ',a
h()
print 'global: ',a
global: 1
f: 1
global: 1
g: 2
global: 1
h: 3
global: 3
>>> c = 1
>>> def foo():
... c = 0
... c += 1
... print c
...
>>> def bar():
... global c
... c += 1
... print c
...
>>> foo()
1
>>> foo()
1
>>> foo()
1
>>> bar()
2
>>> bar()
3
#function
def test_f(x):
y = x + 2
return y
#execute function, and assign result as another variable
var = test_f(3)
#can use the output of test_f()!
print var #returns 5
print var + 3 #returns 8没有像我们在第一个函数中那样声明它 global ，它仍然会给出正确的值。
以 list 为例，您不能在不声明 global 的情况下分配 list，但您可以调用它的方法并更改列表。如下。
testVar = 0
def testFunc():
global testVar
testVar += 1
print testVar
testFunc()
print testVar
>>>
0
1
def testFunc2():
print testVartestVar = []
def testFunc1():
testVar = [2] # Will create a local testVar and assign it [2], but will not change the global variable.
def testFunc2():
global testVar
testVar = [2] # Will change the global variable.
def testFunc3():
testVar.append(2) # Will change the global variable.
count = 0
def funct():
global count
count += 1
return count
print funct() # prints 1
a = funct() # a = 2
print funct() # prints 3
print a # prints 2
print count # prints 3
def initCounter():
count = 0
def incrementCounter():
count += 1
return count
#notice how you're returning the function with no parentheses
#so you return a function instead of a value
return incrementCounter
myFunct = initCounter()
print myFunct() # prints 1
a = myFunct() # a = 2
print myFunct() # prints 3
print a # prints 2
print count # raises an error!
# So you can use count for something else if needed!
a = 1
def f():
# uses global because it hasn't been rebound
print 'f: ',a
def g():
# variable is rebound so global a isn't touched
a = 2
print 'g: ',a
def h():
# specify that the a we want is the global variable
global a
a = 3
print 'h: ',a
print 'global: ',a
f()
print 'global: ',a
g()
print 'global: ',a
h()
print 'global: ',a
global: 1
f: 1
global: 1
g: 2
global: 1
h: 3
global: 3
>>> c = 1
>>> def foo():
... c = 0
... c += 1
... print c
...
>>> def bar():
... global c
... c += 1
... print c
...
>>> foo()
1
>>> foo()
1
>>> foo()
1
>>> bar()
2
>>> bar()
3
#function
def test_f(x):
y = x + 2
return y
#execute function, and assign result as another variable
var = test_f(3)
#can use the output of test_f()!
print var #returns 5
print var + 3 #returns 8一个全局变量可以被任何函数访问，但是只有在函数内部使用'global'关键字显式声明它才能被修改。举个例子，一个实现计数器的函数。你可以用这样的全局变量来做到这一点：
testVar = 0
def testFunc():
global testVar
testVar += 1
print testVar
testFunc()
print testVar
>>>
0
1
def testFunc2():
print testVartestVar = []
def testFunc1():
testVar = [2] # Will create a local testVar and assign it [2], but will not change the global variable.
def testFunc2():
global testVar
testVar = [2] # Will change the global variable.
def testFunc3():
testVar.append(2) # Will change the global variable.
count = 0
def funct():
global count
count += 1
return count
print funct() # prints 1
a = funct() # a = 2
print funct() # prints 3
print a # prints 2
print count # prints 3
def initCounter():
count = 0
def incrementCounter():
count += 1
return count
#notice how you're returning the function with no parentheses
#so you return a function instead of a value
return incrementCounter
myFunct = initCounter()
print myFunct() # prints 1
a = myFunct() # a = 2
print myFunct() # prints 3
print a # prints 2
print count # raises an error!
# So you can use count for something else if needed!
a = 1
def f():
# uses global because it hasn't been rebound
print 'f: ',a
def g():
# variable is rebound so global a isn't touched
a = 2
print 'g: ',a
def h():
# specify that the a we want is the global variable
global a
a = 3
print 'h: ',a
print 'global: ',a
f()
print 'global: ',a
g()
print 'global: ',a
h()
print 'global: ',a
global: 1
f: 1
global: 1
g: 2
global: 1
h: 3
global: 3
>>> c = 1
>>> def foo():
... c = 0
... c += 1
... print c
...
>>> def bar():
... global c
... c += 1
... print c
...
>>> foo()
1
>>> foo()
1
>>> foo()
1
>>> bar()
2
>>> bar()
3
#function
def test_f(x):
y = x + 2
return y
#execute function, and assign result as another variable
var = test_f(3)
#can use the output of test_f()!
print var #returns 5
print var + 3 #returns 8现在，这一切都很好，但通常将全局变量用于除常量之外的任何东西都不是一个好主意。你可以有一个使用闭包的替代实现，这将避免污染命名空间并且更干净：
testVar = 0
def testFunc():
global testVar
testVar += 1
print testVar
testFunc()
print testVar
>>>
0
1
def testFunc2():
print testVartestVar = []
def testFunc1():
testVar = [2] # Will create a local testVar and assign it [2], but will not change the global variable.
def testFunc2():
global testVar
testVar = [2] # Will change the global variable.
def testFunc3():
testVar.append(2) # Will change the global variable.
count = 0
def funct():
global count
count += 1
return count
print funct() # prints 1
a = funct() # a = 2
print funct() # prints 3
print a # prints 2
print count # prints 3
def initCounter():
count = 0
def incrementCounter():
count += 1
return count
#notice how you're returning the function with no parentheses
#so you return a function instead of a value
return incrementCounter
myFunct = initCounter()
print myFunct() # prints 1
a = myFunct() # a = 2
print myFunct() # prints 3
print a # prints 2
print count # raises an error!
# So you can use count for something else if needed!
a = 1
def f():
# uses global because it hasn't been rebound
print 'f: ',a
def g():
# variable is rebound so global a isn't touched
a = 2
print 'g: ',a
def h():
# specify that the a we want is the global variable
global a
a = 3
print 'h: ',a
print 'global: ',a
f()
print 'global: ',a
g()
print 'global: ',a
h()
print 'global: ',a
global: 1
f: 1
global: 1
g: 2
global: 1
h: 3
global: 3
>>> c = 1
>>> def foo():
... c = 0
... c += 1
... print c
...
>>> def bar():
... global c
... c += 1
... print c
...
>>> foo()
1
>>> foo()
1
>>> foo()
1
>>> bar()
2
>>> bar()
3
#function
def test_f(x):
y = x + 2
return y
#execute function, and assign result as another variable
var = test_f(3)
#can use the output of test_f()!
print var #returns 5
print var + 3 #returns 8考虑以下代码：
testVar = 0
def testFunc():
global testVar
testVar += 1
print testVar
testFunc()
print testVar
>>>
0
1
def testFunc2():
print testVartestVar = []
def testFunc1():
testVar = [2] # Will create a local testVar and assign it [2], but will not change the global variable.
def testFunc2():
global testVar
testVar = [2] # Will change the global variable.
def testFunc3():
testVar.append(2) # Will change the global variable.
count = 0
def funct():
global count
count += 1
return count
print funct() # prints 1
a = funct() # a = 2
print funct() # prints 3
print a # prints 2
print count # prints 3
def initCounter():
count = 0
def incrementCounter():
count += 1
return count
#notice how you're returning the function with no parentheses
#so you return a function instead of a value
return incrementCounter
myFunct = initCounter()
print myFunct() # prints 1
a = myFunct() # a = 2
print myFunct() # prints 3
print a # prints 2
print count # raises an error!
# So you can use count for something else if needed!
a = 1
def f():
# uses global because it hasn't been rebound
print 'f: ',a
def g():
# variable is rebound so global a isn't touched
a = 2
print 'g: ',a
def h():
# specify that the a we want is the global variable
global a
a = 3
print 'h: ',a
print 'global: ',a
f()
print 'global: ',a
g()
print 'global: ',a
h()
print 'global: ',a
global: 1
f: 1
global: 1
g: 2
global: 1
h: 3
global: 3
>>> c = 1
>>> def foo():
... c = 0
... c += 1
... print c
...
>>> def bar():
... global c
... c += 1
... print c
...
>>> foo()
1
>>> foo()
1
>>> foo()
1
>>> bar()
2
>>> bar()
3
#function
def test_f(x):
y = x + 2
return y
#execute function, and assign result as another variable
var = test_f(3)
#can use the output of test_f()!
print var #returns 5
print var + 3 #returns 8输出：
testVar = 0
def testFunc():
global testVar
testVar += 1
print testVar
testFunc()
print testVar
>>>
0
1
def testFunc2():
print testVartestVar = []
def testFunc1():
testVar = [2] # Will create a local testVar and assign it [2], but will not change the global variable.
def testFunc2():
global testVar
testVar = [2] # Will change the global variable.
def testFunc3():
testVar.append(2) # Will change the global variable.
count = 0
def funct():
global count
count += 1
return count
print funct() # prints 1
a = funct() # a = 2
print funct() # prints 3
print a # prints 2
print count # prints 3
def initCounter():
count = 0
def incrementCounter():
count += 1
return count
#notice how you're returning the function with no parentheses
#so you return a function instead of a value
return incrementCounter
myFunct = initCounter()
print myFunct() # prints 1
a = myFunct() # a = 2
print myFunct() # prints 3
print a # prints 2
print count # raises an error!
# So you can use count for something else if needed!
a = 1
def f():
# uses global because it hasn't been rebound
print 'f: ',a
def g():
# variable is rebound so global a isn't touched
a = 2
print 'g: ',a
def h():
# specify that the a we want is the global variable
global a
a = 3
print 'h: ',a
print 'global: ',a
f()
print 'global: ',a
g()
print 'global: ',a
h()
print 'global: ',a
global: 1
f: 1
global: 1
g: 2
global: 1
h: 3
global: 3
>>> c = 1
>>> def foo():
... c = 0
... c += 1
... print c
...
>>> def bar():
... global c
... c += 1
... print c
...
>>> foo()
1
>>> foo()
1
>>> foo()
1
>>> bar()
2
>>> bar()
3
#function
def test_f(x):
y = x + 2
return y
#execute function, and assign result as another variable
var = test_f(3)
#can use the output of test_f()!
print var #returns 5
print var + 3 #returns 8基本上，当您需要每个函数访问同一个变量(对象)时，您会使用全局变量。不过，这并不总是最好的方法。
在下面的示例中，我们在任何其他函数之外定义了一个变量 c。在 foo 中，我们还声明了一个 c，将其递增并打印出来。您可以看到重复调用 foo() 将一遍又一遍地产生相同的结果，因为 foo 中的 c 在函数范围内是本地的。
然而，在bar 中，关键字global 被添加到c 之前。现在，变量 c 引用了在全局范围内定义的任何变量 c(即，我们在函数之前定义的 c = 1 实例)。调用 bar 重复更新全局 c 而不是本地范围的。
testVar = 0
def testFunc():
global testVar
testVar += 1
print testVar
testFunc()
print testVar
>>>
0
1
def testFunc2():
print testVartestVar = []
def testFunc1():
testVar = [2] # Will create a local testVar and assign it [2], but will not change the global variable.
def testFunc2():
global testVar
testVar = [2] # Will change the global variable.
def testFunc3():
testVar.append(2) # Will change the global variable.
count = 0
def funct():
global count
count += 1
return count
print funct() # prints 1
a = funct() # a = 2
print funct() # prints 3
print a # prints 2
print count # prints 3
def initCounter():
count = 0
def incrementCounter():
count += 1
return count
#notice how you're returning the function with no parentheses
#so you return a function instead of a value
return incrementCounter
myFunct = initCounter()
print myFunct() # prints 1
a = myFunct() # a = 2
print myFunct() # prints 3
print a # prints 2
print count # raises an error!
# So you can use count for something else if needed!
a = 1
def f():
# uses global because it hasn't been rebound
print 'f: ',a
def g():
# variable is rebound so global a isn't touched
a = 2
print 'g: ',a
def h():
# specify that the a we want is the global variable
global a
a = 3
print 'h: ',a
print 'global: ',a
f()
print 'global: ',a
g()
print 'global: ',a
h()
print 'global: ',a
global: 1
f: 1
global: 1
g: 2
global: 1
h: 3
global: 3
>>> c = 1
>>> def foo():
... c = 0
... c += 1
... print c
...
>>> def bar():
... global c
... c += 1
... print c
...
>>> foo()
1
>>> foo()
1
>>> foo()
1
>>> bar()
2
>>> bar()
3
#function
def test_f(x):
y = x + 2
return y
#execute function, and assign result as another variable
var = test_f(3)
#can use the output of test_f()!
print var #returns 5
print var + 3 #returns 8在函数中使用 global <variable name> 显式声明应该会有所帮助
几天来我一直在努力解决同样的问题/误解了我想要的东西，我认为您可能想要完成的是让函数输出结果，可以在函数完成运行后使用。
您可以在上面完成的方法是使用返回"一些结果"，然后将其分配给函数之后的变量。
下面是一个例子：
testVar = 0
def testFunc():
global testVar
testVar += 1
print testVar
testFunc()
print testVar
>>>
0
1
def testFunc2():
print testVartestVar = []
def testFunc1():
testVar = [2] # Will create a local testVar and assign it [2], but will not change the global variable.
def testFunc2():
global testVar
testVar = [2] # Will change the global variable.
def testFunc3():
testVar.append(2) # Will change the global variable.
count = 0
def funct():
global count
count += 1
return count
print funct() # prints 1
a = funct() # a = 2
print funct() # prints 3
print a # prints 2
print count # prints 3
def initCounter():
count = 0
def incrementCounter():
count += 1
return count
#notice how you're returning the function with no parentheses
#so you return a function instead of a value
return incrementCounter
myFunct = initCounter()
print myFunct() # prints 1
a = myFunct() # a = 2
print myFunct() # prints 3
print a # prints 2
print count # raises an error!
# So you can use count for something else if needed!
a = 1
def f():
# uses global because it hasn't been rebound
print 'f: ',a
def g():
# variable is rebound so global a isn't touched
a = 2
print 'g: ',a
def h():
# specify that the a we want is the global variable
global a
a = 3
print 'h: ',a
print 'global: ',a
f()
print 'global: ',a
g()
print 'global: ',a
h()
print 'global: ',a
global: 1
f: 1
global: 1
g: 2
global: 1
h: 3
global: 3
>>> c = 1
>>> def foo():
... c = 0
... c += 1
... print c
...
>>> def bar():
... global c
... c += 1
... print c
...
>>> foo()
1
>>> foo()
1
>>> foo()
1
>>> bar()
2
>>> bar()
3
#function
def test_f(x):
y = x + 2
return y
#execute function, and assign result as another variable
var = test_f(3)
#can use the output of test_f()!
print var #returns 5
print var + 3 #returns 8普通变量只能在函数内部使用，全局变量可以在函数外部调用，但如果不需要，请不要使用它，它会产生错误，大型编程公司认为这是一个菜鸟要做的事情。