如何让函数在被调用时相互感知，例如使用 ElementTree 包时

Question

如果标题问题表述不清楚，下面的代码会更好的解释。此代码工作正常：

#!/usr/bin/python3
import sys
import os
import xml.etree.ElementTree as ET
from xml.etree.ElementTree import *

country_arg = 'usa'
transport_name_arg = 'train'
route_data = "some route"

world = ET.Element('world')
country = ET.SubElement(world, 'country')
country.text = country_arg
event = ET.SubElement(world, 'event')
transport = ET.SubElement(event, 'transport')
transport.set('name',transport_name_arg)
route = ET.SubElement(event, 'route')

comment = Comment(route_data)
route.append(comment)
c = ET.SubElement(event, 'c')

tree = ET.ElementTree(world)
tree.write("filename.xml")

但是我需要创建和使用在实际脚本的不同位置调用它们的函数。我认为当函数运行时它与它所代表的代码块运行时相同。然而， function_1 的结果似乎没有保存在内存中？这是与上面相同的脚本，但代码被分成两个函数并且它不起作用，就好像一旦 function_2 被调用，function_1 的结果就丢失了：

#!/usr/bin/python3
import sys
import os
import xml.etree.ElementTree as ET
from xml.etree.ElementTree import *

country_arg = 'usa'
transport_name_arg = 'train'
route_data = "some route"

def function_1():
    world = ET.Element('world')
    country = ET.SubElement(world, 'country')
    country.text = country_arg
    event = ET.SubElement(world, 'event')
    transport = ET.SubElement(event, 'transport')
    transport.set('name',transport_name_arg)
    route = ET.SubElement(event, 'route')

def function_2():
    comment = Comment(route_data)
    route.append(comment)
    c = ET.SubElement(event, 'c')

function_1()
function_2()

tree = ET.ElementTree(world)
tree.write("filename.xml")

错误：

Traceback (most recent call last):
  File "test-WITH-functions-xml.py", line 26, in <module>
    function_2()
  File "test-WITH-functions-xml.py", line 22, in function_2
    route.append(comment)
NameError: name 'route' is not defined

Answer 1

这段代码有效，谢谢大家，很好的学习经验：

#!/usr/bin/python3
import sys
import os
import xml.etree.ElementTree as ET
from xml.etree.ElementTree import *

country_arg = 'usa'
transport_name_arg = 'train'
route_data = "some route"

def function_1():
    global world
    global country
    global event
    global transport
    global route
    world = ET.Element('world')
    country = ET.SubElement(world, 'country')
    country.text = country_arg
    event = ET.SubElement(world, 'event')
    transport = ET.SubElement(event, 'transport')
    transport.set('name',transport_name_arg)
    route = ET.SubElement(event, 'route')

def function_2():
    global comment
    global c
    comment = Comment(route_data)
    route.append(comment)
    c = ET.SubElement(event, 'c')

function_1()
function_2()

tree = ET.ElementTree(world)
tree.write("filename.xml")

如何让函数在被调用时相互感知，例如使用 ElementTree 包时

How to make the functions be aware of each other when they are called, e.g. when using the ElementTree package

xml

function

elementtree

python-3.x