Zed Shaw，练习 16 [重复]

Question

我正在阅读 Zed Shaw 的 Python 书。现在我正在尝试通过稍微调整来进一步完成练习 16：

from sys import argv

script, filename = argv

print "We're going to erase %r." % filename
print "If you don't want that, hit CTRL-C (^C)."
print "If you do want that, hit RETURN."

raw_input("?")

print "Opening the file..."
target = open(filename, 'r+')
print "Displaying the file contents:"
print target.read()

print "Truncating the file. Goodbye!"
target.truncate()

print "Now I'm going to ask you for three lines."

line1 = raw_input("line 1: ")
line2 = raw_input("line 2: ")
line3 = raw_input("line 3: ")

print "I'm going to write these to the file."

target.write(line1)
target.write("\n")
target.write(line2)
target.write("\n")
target.write(line3)
target.write("\n")

print "And finally, we close it."
target.close()

请注意，我使用“r+”而不是“w”，因为我想在练习中读写，但发生了一些事情：target.truncate() 不起作用；文件中的信息仍然存在。为什么程序会这样进行？

Answer 1

truncate

默认在 current 位置截断文件，在

read

调用后，该位置将位于文件末尾。如果您想清除整个文件，请使用

truncate(0)

。