fileObject.truncate( [ size ])

假设 'foo.txt' 文件包含以下文本：
This is 1st line
This is 2nd line
This is 3rd line
This is 4th line
This is 5th line

#!/usr/bin/python3

fo = open("foo.txt", "r+")
print ("文件名为: ", fo.name)

line = fo.readline()
print ("读取行: %s" % (line))

fo.truncate()
line = fo.readlines()
print ("读取行: %s" % (line))

# 关闭已打开的文件
fo.close()

文件名为: foo.txt
读取行: This is 1s
读取行: []