Python 大小写转换

def low_UPER():
oldNme='demo.txt'
newName='my.txt'
fp = open(oldNme,"r+")
newFp = open(newName,"w")
for eachline in fp.readlines():
newStr = eachline.replace(" ","").replace("\t","").strip()

print "Write:",newStr

newFp.write(newStr.upper())
fp.close()
newFp.close()
#
doc=os.getcwd()
mytree=os.listdir(doc)
print mytree
for i in mytree:
if i == oldNme:
mytree.remove(i)
os.rename(newName,oldNme)