用比较笨的方法实现了一下

with open('logtest.txt','r',encoding='utf-8') as f:
list=[]
for lines in f:
list.append(lines.split())

api_name={}
count={}
for i in list:
if i[0] not in api_name:
api_name.update({i[0]:(0-int(i[2]))})
count.update({i[0]:int("1")})
else:
if i[1] =="end":
api_name.update({i[0]:(int(i[2])+int(api_name[i[0]]))})
count.update({i[0]:(count[i[0]]+1)})
if i[1] == "start":
api_name.update({i[0]:(int(api_name[i[0]]-int(i[2])))})
count.update({i[0]:(count[i[0]]+1)})

for i in count.keys():
print('api',i,"average running time =",api_name[i] / count[i])