关于python etree文件操作的一个问题

Question

#coding=utf-8 

import tempfile 
import os 
import re 
import time 
import xml.etree.cElementTree as ET


def uidump():
os.popen("adb shell uiautomator dump /data/local/tmp/uidump.xml")
os.popen("adb pull /data/local/tmp/uidump.xml D:/ ")


def element(attrib, name):
"""
同属性单个元素，返回单个坐标元组
"""
uidump()
with open("uidump.xml",'r+', encoding="utf-8" ,errors='ignore') as xml_file:
tree = ET.parse(xml_file)
treeIter = tree.iter(tag="node")
for elem in treeIter:
if elem.attrib[attrib] == name:
bounds = elem.attrib["bounds"]
coord = re.compile(r"\d+").findall(bounds)
Xpoint = (int(coord[2]) - int(coord[0])) / 2.0 + int(coord[0])
Ypoint = (int(coord[3]) - int(coord[1])) / 2.0 + int(coord[1])

return Xpoint, Ypoint
uidump()
e1=element("text","公众号")
我写了一个代码， 从python调用adb连接安卓手机，通过一个名为uidump.xml的文件解析当前界面的信息，但是执行后一直提示FileNotFoundError: [Errno 2] No such file or directory: 'uidump.xml'，即解析之前不会先拉取文件，而是先解析然后报错之后会正常拉取文件，这是什么原因呢？谢谢！