python如何判断一个文件的行数

#encoding=utf-8

#文件比较小

count=len(open(r"train.data",'rU').readlines())

print(count)

#文件比较大

count=-1

for count, line in enumerate(open(r"train.data",'rU')):

pass

count+=1

print(count)

#更好的方法

count=0

thefile=open("train.data")

while True:

buffer=thefile.read(1024*8192)

if not buffer:

break

count+=buffer.count('\n')

thefile.close()

print(count)