问题
I'm learning python, and am having a problem with global variables/lists. I'm writing a basic manual tower of hanoi program, here's the program currently:
pilar1 = [5,4,3,2,1,0]
pilar2 = [0,0,0,0,0,0]
pilar3 = [0,0,0,0,0,0]
def tower_of_hanoi():
global pillar1
global pillar2
global pillar3
print_info()
def print_info():
global pillar1
global pillar2
global pillar3
for i in range(4,-1,-1):
print(pillar1[i], " ", pillar2[i], " ", pillar3[i])
I've tried a few variations, but every time I got the error "NameError: global name 'pillar1' is not defined".
What would be the best way to handle a global list in this setting? I'd prefer to just use one source file, if possible. Thanks!
回答1:
It's because you've "declared" it as pilar1, not pillar1
回答2:
The problem you encounter is pilar not being the same as pillar.
After you fix that, you will no longer need the global declarations:
pilar1 = [5,4,3,2,1,0]
pilar2 = [0,0,0,0,0,0]
pilar3 = [0,0,0,0,0,0]
def tower_of_hanoi():
print_info()
def print_info():
for i in range(4,-1,-1):
print(pillar1[i], " ", pillar2[i], " ", pillar3[i])
Only time you need to use global is if you assign a global variable in a non-global scope, such as function definition:
# global variable, can be used anywhere within the file since it's
# declared in the global scope
my_int = 5
def init_list():
# global variable, can be used anywhere within the file after
# init_list gets called, since it's declared with "global" keyword
global my_list
my_list = [1, 2, 3]
def my_function():
# local variable, can be used only within my_function's scope
my_str = "hello"
# init's global "my_list" variable here, which can then be used anywhere
init_list()
my_list.append(5)
my_function()
print(my_list)
However you shouldn't use globals too much, instead use function parameters to pass values around.
来源：https://stackoverflow.com/questions/14402557/python-global-lists