我的Python程序太慢了。我该如何提速？

newlist = []for word in oldlist:   newlist.append(word.upper())

newlist = map(str.upper, oldlist)

newlist = [s.upper() for s in oldlist]

iterator = (s.upper() for s in oldlist)

def func():   upper = str.upper   newlist = []   append = newlist.append   for word in oldlist:      append(upper(word))   return newlist

from time import timemyStr =''a='gjhbxjshbxlasijxkashxvxkahsgxvashxvasxhbasxjhbsxjsabxkjasjbxajshxbsajhxbsajxhbasjxhbsaxjash'l=[]# Using the + operatort=time()for i in range(1000):   myStr = myStr+a+repr(i)print(time()-t)

0.003464221954345703

from time import timemyStr =''a='gjhbxjshbxlasijxkashxvxkahsgxvashxvasxhbasxjhbsxjsabxkjasjbxajshxbsajhxbsajxhbasjxhbsaxjash'l=[]# Using the + operatort=time()for i in range(1000):   l.append(a + repr(i))z = ''.join(l)print(time()-t)

0.000995635986328125