如何在 python 函数中使用全局变量？

testVar = 0

def testFunc():
    global testVar
    testVar += 1

print testVar
testFunc()
print testVar

>>>
0
1

def testFunc2():
    print testVar

testVar = []
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